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. 2026 Apr 1;109(1):478–493. doi: 10.1111/jfb.70397

Reproductive biology of the starry grouper, Epinephelus labriformis (Perciformes: Serranidae): Gonadal development, sex change and sexual pattern

Rebeca Sánchez‐Cardenas 1, Josué López‐Cardiel 1, Juan Manuel Martínez‐Brown 2, Luis Antonio Rendón‐Martínez 3, Rodrigo Martínez‐Moreno 4, Leonardo Ibarra‐Castro 5,6,✉
PMCID: PMC13397241  PMID: 41919985

Abstract

The reproductive biology of the starry grouper, Epinephelus labriformis, in Mazatlan Bay, Mexico, was studied through histological analysis of the gonads. A total of 527 fish were examined through weekly sampling from March 2017 to March 2018. In this species, the gonads are bilobed and connected to a common gonoduct. E. labriformis exhibits monandric protogynous hermaphroditism, with a female‐to‐male proportion of 1.5 females:1 male in fully mature animals. In females, six ovarian phases were identified, and the oogenic cycle was analysed in 314 females, classified as asynchronous. The gonadosomatic index increased from 0.13 in the immature phase to 3.35 at maturity, declining to 1.16 post‐spawning. Transforming testes (n = 95) revealed four stages of sex change, during which ovarian tissue is progressively replaced by testicular tissue. Males and transforming individuals appeared in larger size classes, with no females recorded beyond 27.5 cm total length (L t). Females reach sexual maturity at 17.2 cm L t. In comparison, males mature at 19.42 cm L t. Sex change occurs in individuals with total lengths ranging from 20 cm to 33.5 cm L t, with an average size for sex change of 24.7 cm. Our findings define the reproductive strategy of E. labriformis. They also provide actionable guidelines for fisheries management in Mexico. In the absence of specific regulations in Mexico, we recommended establishing a minimum catch size between 24 and 27 cm L t and seasonal protection during the reproductive period to preserve spawning potential and maintain a balanced sex ratio in the population.

Keywords: grouper, hermaphroditism, histology, protogyny, reproduction

1. INTRODUCTION

The family Epinephelidae (Actinopteri: Perciformes) includes 16 genera and 176 valid species worldwide (Fricke et al., 2025). In the Tropical Eastern Pacific, this family is represented by the genera Alphestes, Dermatolepis, Cephalopholis, Epinephelus, Hyporthodus and Mycteroperca (Robertson & Allen, 2024). Most of the species in this family are of commercial interest (Aburto‐Oropeza et al., 2008). Epinephelus labriformis, commonly known as the starry grouper, is distributed from Baja California and the Gulf of California (Mexico) to Peru, including Revillagigedo (Mexico), Coco (Costa Rica) and the Galapagos Islands (Ecuador) (Froese & Pauly, 2025). Adults inhabit rocky terrain and coral reefs at depths up to 50 m (Robertson & Allen, 2015), while juveniles inhabit shallower, more protected reefs and mangroves areas (Aburto‐Oropeza et al., 2008). E. labriformis plays a key ecological role as a mesopredator in reef communities (Aburto‐Oropeza et al., 2008), preying on fishes, octopuses, squids, shrimps and crabs (Raymundo‐Huizar, 2016). Consequently, uncontrolled extraction of E. labriformis may reduce both its population and its ecological function in reef ecosystems (Coleman et al., 1996; Erisman et al., 2010; Ruiz‐Ramírez et al., 2018).

The family Epinephelidae exhibits protogynous hermaphroditism as its predominant reproductive strategy (Pla et al., 2022). An individual who is hermaphroditic switches its sex to the opposite sex at some stage of their life. However, to be classified as a hermaphrodite, the majority of individuals in the population must possess the hermaphroditic reproduction pattern (Sadovy & Shapiro, 1987). Among 294 hermaphroditic teleost species reviewed by Pla et al. (2022), most (84.4%) were sequential hermaphrodites, while the remainder (15.6%) were simultaneous hermaphrodites. Within sequential hermaphrodites, protogyny is the most common form (79%), followed by protandry (14.5%) and bidirectional hermaphroditism (6.5%). In protogynous species, individuals first mature as females and later change sex to males. Protogynous species may form either monandric and diandric populations: in monandric populations all males arise from sex‐changed females and are termed secondary males (Sadovy & Shapiro, 1987), whereas in diandric populations, two male types occur, primary males (maturing directly as males) and secondary males (derived from females) (Sadovy & Shapiro, 1987; Warner, 1975).

In the Epinephelidae family, we have monandric‐type species such as E. aeneus (Bruslé & Bruslé, 1975), E. drummondhayi (Brulé et al., 2000), E. guttatus (Sadovy, Rosario, & Roman, 1994), E. marginatus (Bruslé & Bruslé, 1975), E. morio (Brulé et al., 1999; Moe, 1969) and Plectropomus leopardus (Ferreira, 1995). Based on the above information, monandry is common among protogynous hermaphrodites in the Epinephelidae family, where all males are considered secondary, derived from sex‐changed females, therefore it is expected that E. labriformis exhibits protogynous hermaphroditism with monandrous populations, as this species has been reported to date as a protogynous hermaphrodite (Del Moral‐Flores, 2007; Hernández‐Flores, 2015; Ruiz‐Ramírez et al., 2018). To date, male individuals have not been clearly identified at the smallest sizes (<19 cm total length [L t]) (Del Moral‐Flores, 2007), and no resting phase has been observed in males under examination with the naked eye (Hernández‐Flores, 2015). On the other hand, immature males have been observed in larger size individuals (>19 cm L t), but no histological evidence was described (Ruiz‐Ramírez et al., 2018), leaving uncertainty as to whether these individuals represent primary, secondary or both male types. Identifying the type of hermaphroditism can be challenging if the sampling does not encompass a wide range of fish sizes and if the sampling periods for the organisms are too infrequent. This was the case of E. striatus, which had been initially reported as a protogynous hermaphrodite (Colin, 1992); however, it was subsequently reported that the sexual pattern present in this species showed a bisexual stage in the juvenile period and was gonochoric in the adult stage (Sadovy & Colin, 1995). Another similar case is that of Paralabrax nebulifer, in which a gonochoric sexual pattern was diagnosed; however, it has the potential for sex change (Baca‐Hovey et al., 2002). Due to this, it can be hypothesized that hermaphroditism in Epinephelidae exhibits a wide range of plasticity and its accurate diagnosis requires species‐specific histological evidence across a broad range of sizes (Sadovy & Colin, 1995).

To design and implement conservation and management plans for Epinephelidae fish on the Mexican Pacific coast, specifically in the state of Sinaloa, it is essential to understand their reproductive biology. E. labriformis is highly vulnerable to fishing pressure and requires management measures to ensure sustainable stock replacement. In fact, overexploitation can affect the population dynamics of protogynous hermaphroditic species in three ways: (i) reducing the abundance of males limits the ability to fertilize eggs, (ii) the replacement of missing males by more dominant (usually larger) females could reduce the average size of active females and thus the fecundity of the breeding group, and (iii) spawning disruption occurs due to reduction of one of the sexes in the population structure (Bannerot, 1987; Coleman et al., 2000; Huntsman et al., 1999; Koenig et al., 1996; Rhodes & Sadovy, 2002; Sadovy & Liu, 2008; Vincent & Sadovy, 1998). Such imbalances can reduce recruitment and lead to a progressive decline in population, therefore understanding the sexual pattern, size at maturity and size at sex change in E. labriformis is essential for interpreting and predicting population dynamics. We hypothesize that E. labriformis from the coast of Mazatlan, Sinaloa, Mexico, exhibits monandric protogynous hermaphroditism within a population composed primarily of females and secondary males, with a predominance of females in smaller sizes and males in larger sizes. To test this hypothesis, we examined the sexual pattern and reproductive biology of E. labriformis, characterizing gonadal development, sequential sex change, size at sexual maturity, size at sex change and overall sexual composition. The findings provide new insight into the species' reproductive biology and may support the development of management measures within Mexico's National Fishing Charter (D.O.F. 08/25/2006).

2. MATERIALS AND METHODS

2.1. Fish gonad samples

Fish samples were collected from the artisanal fishing fleet at Playa Norte beach, Mazatlan Bay, Sinaloa, Mexico. Fishing trips were conducted in nearshore areas in the southwestern Gulf of California (23.17°N, 106.38 W to 23.31°N, 106.49 W). Samples were collected in rocky bottom regions and fishing grounds near local islands and the coastline, at depths ranging from 5 to 30 m, representing the primary habitats where E. labriformis are found. The fishers used a handline and squid as bait to catch the fish. The fish caught were placed in a livewell on the fishing boat, keeping them alive until they arrived at the landing place in Playa Norte beach, where they were transferred to a 500 L saltwater tank with pure oxygen bubblers and then transported to the laboratory facility. At the laboratory, the fish were sacrificed with an overdose of clove oil. Subsequently, the total weight (W ± 1 g) and total length (L t ± 0.1 cm) were obtained. Then, the fish were dissected, and the liver weight (W L ± 0.01 g), gonad weight (W G ± 0.01 g) and eviscerated fish weight (W E ± 1 g) were recorded. All gonads were fixed in 10% formalin for 24 h, then rinsed and preserved in 70% ethyl alcohol until histological examination. From March 2017 to March 2018, we selected 10 fish weekly from artisanal fishing.

2.2. Histological techniques

Ovaries and testes were sectioned to obtain a cross‐section of the middle part of the gonadal lobe. Briefly, testicular and ovarian tissues were dehydrated and cleared with isopropyl alcohol and mineral oil treatments, then were impregnated with liquid paraffin (Buesa & Peshkov, 2009) and included in paraffin blocks. From these blocks, 5 μm thick sections were obtained using a Thermo Fisher Scientific HM355S microtome, then mounted on slides and stained using the Harris haematoxylin–eosin stain technique (Bancroft & Gamble, 2013; Humason, 1979). Once the tissues were stained, synthetic resin (Cytoseal) was applied to the tissue and a cover slip was placed for protection, storage and subsequent observation. Histological preparations were observed and photographed using an optical microscope (Carl Zeiss Axiolab 5, Axiocam 208 colour camera system).

2.3. Histological data

From all histological sections, we took colour digital magnification photographs, from which quantitative data were recorded. We randomly measured the diameter (D ± 0.1 μm) of 1300 oocytes with a visible nucleus and 160 spermatogenic cells at different stages of maturation. Measurements were made using the Sigma Scan Pro software (version 5.0, Systat Software, Inc.). The area (A) of each cell was measured, and then their diameters (D) were calculated from a geometric formula for a circle (Baldor, 2019). Estimates of the mean D were calculated for each oogenenic stage and different gonadal phases. The gonadal wall width (W W ± 0.1 μm) was measured from 527 histological sections and the mean (W W) was calculated for each gonadal phase. The number of oocytes in one gonadal lamellae (Ol) was recorded from histological sections of gonads in the process of sex change (n = 95), and the average number of Ol was calculated per transitional sex‐change phase. The number of atretic oocytes (Al) was recorded for each histological section.

2.4. Gonadal development

Female and male gonadal developmental patterns in E. labriformis were described from 527 fish. The gonadal development phases were described following accepted stages (Schulz et al., 2010; Wallace & Selman, 1981; West, 1990); Brown‐Peterson et al., 2011; Maldonado‐Amparo et al., 2017; Márquez‐Cuétara, 2018; Ruiz‐Ramírez et al., 2018. However, the descriptions were complemented with additional characteristics and criteria to better characterize the gonadal cycle, including distinctions between subphases (Brown‐Peterson et al., 2011). The diagnosis considered cellular and tissue characteristics, such as oogenesis and spermatogenesis germ cell stages, ovary and testicle wall thickness, and the presence/absence of post‐ovulatory follicles, atresia and oocyte coverage (Oc, ~%). In addition, the D per oogenesis stage was estimated for each ovarian developmental phase (ODP) and the gonadosomatic index (GSI ± standard error) was estimated for each ODP and testicular development phase (TDP) according to Devlaming et al. (1982). We incorporated W G and W E, at each stage looking for more representative information than just the GSI. Organisms with testicular tissue and lamellae with oocytes at any stage of development were considered active‐transforming males (ATMs) if they presented sperms crypts or spermatozoa in their testicular tissue, and if they did not, they were deemed inactive‐transforming males (ITMs) (Lluch‐Cota, 1995), and their gonads were called transforming testicles (TTs).

2.5. Sex‐change process

The sex‐change process by which the ovary loses the female tissue as it adopts a male function was described by sex‐change stages (SCSs). These stages were defined based on 95 histological preparations of gonads undergoing sex change, presenting both male and female tissue, following the observations proposed by Mackei (2000), Estrada‐Godínez et al. (2011) and Ruiz‐Ramírez et al. (2018). The SCS was defined based on attributes such as the presence and stages of oocytes, spermatocytes, spermatids and sperm, number of oocytes in one gonadal lamellae (Ol), thickness of the ovarian wall (W W), testicular tissue coverage (T c, ~%), presence of post‐ovulatory follicles, atresia, crypts, and the organization and architecture of the gonadal tissue.

2.6. Sexual composition

The population's sexual composition and sex‐size structure were analysed by the number of females per male. This sex ratio (n:1) was calculated by dividing the number of females by the number of males for the total sample and for each size interval. The sex ratio (n:1) was compared with an expected ratio of 1:1, using a chi‐squared test (χ 2) with a significance value of α = 0.05 (Zar, 2010). Additionally, the percentage of females, ITMs, ATMs and males was calculated for each size interval.

2.7. Size at sexual maturity

The size at sexual maturity (L m50), defined as the size at which 50% of organisms are adults (Binohlan, 1998), was estimated from the logistic model Y = 1/1 + AeBX, where Y is the adult ratio for the midpoint of a class interval of L t (X), and A, B and C are undetermined parameters (Somerton, 1980). The model was fitted separately by sex using the method of minimizing the sum of squared residuals (Siegel & Loeb, 1994). The class intervals of L t were 1 cm and the adult ratio was estimated by dividing the number of adults by the total number of individuals (juveniles plus adults) in the class interval. The sizes at which 60% (L m60), 70% (L m70), 80% (L m80), 90% (L m90) and 99% (L m99) of organisms are adults (Froese & Binohlan, 2000) were also calculated from the model. The minimum size at sexual maturity (L mα) was defined as the size of the smallest observed adult. The L m99 was considered the maximum size at sexual maturity (L mω). All estimations were made separately for females and males.

2.8. Size at sex change

The size at sex change (L c50) or the size at which 50% of sex‐transitional individuals in the population has occurred was estimated from the logistic model Y = 1/1 + AeBX, where Y is the cumulative proportion of sex‐transitional individuals for the midpoint of a class interval of L t (X), and A, B and C are undetermined parameters. The model was fitted using the minimization method of the sum of squared residuals (Siegel & Loeb, 1994). The class intervals of L t were 1 cm and the cumulative proportion of sex‐transitional individuals was estimated by dividing the number of sex‐transitional individuals (ITMs and ATMs) in the class interval of L t by the total number of sex‐transitional organisms in the population's sample. The sizes at which 60% (L c60), 70% (L c70), 80% (L c80), 90% (L c90) and 99% (L c99) of sex‐transitional individuals have occurred were also calculated from the model. The minimum size at sex change (L cα) was defined as the size of the smallest sex‐transitional individual. The L c99 was considered the maximum size at sex change (L cω).

2.9. Characterization and classification of hermaphroditism

The protogynous hermaphroditism of E. labriformis was reassessed to define more details of the sexual pattern and the protogyny subtype. This was performed through detailed diagnosis based on qualitative and quantitative histological data, primarily considering the criteria of Reinboth (1962, 1980), Smith (1965), Warner (1975), Sadovy and Shapiro (1987), and Lluch‐Cota (1995). The attributes considered in the analysis were the percentage of individuals in sexual transition, the presence of atretic bodies within the gonads, the architecture of gonadal stroma before, during and after the sex change, the population's sexual composition by size, the width of the ovary wall (W W), the number of oocytes in lamellae (Ol), the number of atretic oocytes (Al), testicular tissue coverage (Tc) and the start of spermatids and spermatozoa.

3. RESULTS

3.1. Gonad

The ovary and testes consist of two lobules fused at the posterior end, connecting to the gonoduct leading to the genital pore. In both, the gonadal stroma consists of tissue folds or lamellae that both contain and provide support to oogenesis or spermatogenesis. These structures are connected to the proximal region, covering approximately half of the ovarian or testicle lobe's wall (Figure 2f1).

FIGURE 2.

FIGURE 2

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Photomicrographs of histological sections of the testicular developmental phases and sub‐phases from Epinephelus labriformis. (a1, a2) Inactive showing thick wall (tw) spermatocytes (sc), perinucleolar oocytes (pn) and red blood cells (rbc) (tw). (b1) Early development showing spermatogonia (sg) and spermatocytes (sc). (b2) Advanced development showing spermatogonia (sg), spermatocytes (sc) and spermatozoa (sz). (c1) Intensive ejaculation showing spermatozoa (sz). (c2) Final ejaculation showing spermatocytes (sc) and spermatozoa (sz). (d1, d2) Post‐ejaculation showing brown cells (bc). (e1–e4) The gain in testicular tissue coverage during sex change: (e1) sex‐change stages I; (e2) sex‐change stage II; (e3) sex‐change stage, showing spermatocytes, spermatozoa and more less perinucleolar oocytes per lamellae; (e4) sex‐change stages IV. (e1) Gonadal architecture showing the proximal conection, position and compaction of the ovarian lamellae in across section. The Harris haematoxylin–eosin stain technique was used.

3.2. Gonadal development

3.2.1. Oogenesis in E. labriformis

We examined gonadal development in 314 females. We identified 10 different stages in this process: oogonia (D = 5.03 ± 0.13 μm), chromatin nucleus (D = 49.34 ± 0.42 μm), perinucleolar (D = 78.28 ± 0.77 μm), cortical alveolus (D = 120.70 ± 1.89 μm), vitellogenesis‐I (D = 159.49 ± 1.91 μm), vitellogenesis‐II (D = 241.62 ± 2.94 μm), vitellogenesis‐III (D = 355.53 ± 1.94 μm), migratory nucleus (D = 373.55 ± 6.01 μm), coalescence (D = 373.55 ± 6.01 μm) and hydrated (D = 281.32 ± 10.07 μm) (Figure 1). From the oogonia stage to vitellogenesis‐III, germinal cell size increased by 85.3% during the ovogenesis process. At the perinucleolar oocyte stage, we observed an average of 4.3 ± 0.30 nucleoli in the nucleus periphery. Subsequently, after vitellogenesis‐III, we observed the migratory nucleus oocyte stage, with an average diameter of the nucleus of 15.47 ± 0.87 μm. The formation of lipid droplets around the nucleus characterized the initial stage of maturation. This maturation process continued until a single lipid droplet became visible, preceding the hydration and ovulation stages.

FIGURE 1.

FIGURE 1

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Photomicrographs of histological sections of the ovarian developmental phases and sub‐phases from Epinephelus labriformis. (a1–a3) Immature showing oogonia (oo), chromatin nucleolar oocytes (cn), perinucleolar oocytes (pn) and the thin ovarian wall. (b1) Early development showing cortical alveolar oocytes (ca). (b2) Advanced development showing vitellogenesis primary oocytes (v‐I), vitellogenesis secondary oocytes (v‐II) and vitellogenesis tertiary oocytes (v‐III). (c1, c2) Maturity showing vitellogenesis tertiary oocytes (v‐III), coalescence oocytes (c) and hydrated oocytes (h). (d1, d2) Spawning showing postovulatory follicles (pof). (e1, e2) Recovering showing atretic oocytes (at). (f1, f2) Rest ovary showing the thick wall (ow), oogonia (oo) and perinucleolar oocytes (pn). The Harris haematoxylin–eosin stain technique was used.

The ovarian cycle in E. labriformis was described as consisting of six ODPs: immature, development, maturity, spawning, recovering and rest (see Table 1 and Figure 1). Additionally, two sub‐phases within the development phase were distinguished in the ovaries: early and advanced. From the immature phase to the maturity phase, the gonadosomatic index (GSI) increased from an average of 0.13 ± 0.014 to 3.35 ± 0.27. During the recovery phase (after the female's spawn), the GSI decreased to 1.16 ± 0.10. In the rest phase, the average GSI was 0.37 ± 0.041. This final phase marks the beginning of the new ovarian cycle. While the immature and rest phases share similarities in size and stromal features, they can be differentiated by the width of the ovarian wall (Figure 1a1,f1). In this case, the average width was 33.22 ± 1.84 μm (n = 40) for the immature phase and 60.59 ± 3.03 μm (n = 58) for the rest phase.

TABLE 1.

Ovarian and testicular developmental phases (ODP and TDP) and sub‐phases in Epinephelus labriformis.

Ovarian developmental phases Testicular developmental phases
Immature: The oocyte stages present are chromatin nucleus and perinucleolar in lamellae. The ovary walls are thin (W W = 33.22 ± 1.84 μm). The wall and stroma are well compacted. The GSI is 0.13 ± 0.01 g (Figure 1a1–a3)

The immature phase was not found in the testicles. Instead, the inactive phase was described.

Inactive: The spermatogonia and spermatocytes occur together with remnant oocytes at any oogenesis stage in lamellae. The distribution of spermatocytes and oocytes is undelimited. There are not spermatozoa. The W W is 91.40 ± 36.68 μm. The GSI is 0.31 ± 0.11 g (Figure 2a1).
Development phase Development phase

Early development sub‐phase: The chromatin nucleus and perinucleolar oocytes are still present, and in addition occur cortical alveolus, and vitellogenesis‐I oocyte stages. The W W is 36.88 ± 1.27 μm. The GSI is 1.24 ± 0.20 g (Figure 1b1)

Advanced development sub‐phase:

In addition to the oocyte stages observed at the last sub‐phase, the advanced development is distinguished by the presence and large coverage of oocytes in vitellogenesis II and vitellogenesis III of about 60–80%. The W W is 41.13 ± 1.99 μm. The GSI is 2.28 ± 0.21 g (Figure 1b2).

Early development sub‐phase: The spermatogonia, spermatocytes and spermatids in proliferation are present. They could co‐occur with remnant oocytes at any oogenesis stage. The spermatozoa are contained only in spermatic crypts or acini. The W W is 37.15 ± 4.26 μm. The GSI is 0.24 ± 0.07 g (Figure 2b1)

Advanced development sub‐phase: In addition to the observed at the last sub‐phase, all the cell stages of spermatogenesis are more abundant in spermatic crypts. Also, a small amount of spermatozoa is found in the ejaculation or efferent ducts. The W W is 25.16 ± 4.11 μm. The GSI is 0.16 ± 0.01 g (Figure 2b2).
Maturity phase: The oocytes in previtellogenesis (chromatin nucleus, perinucleolar and cortical alveolus) are present. All or some vitellogenesis (I, II and III) stages can be observed simultaneously in this phase. In addition, the presence of oocytes in final maturation (migratory nucleus, coalescence or hydrated stages) is the distinctive feature of this phase. The W W is 36.34 ± 2.06 μm. The GSI is 3.52 ± 0.38 g (Figure 1c1,c2).

Ejaculation phase

Intensive ejaculation sub‐phase: The spermatocytes, spermatids and spermatozoa are abundant in spermatic crypts. In addition, spermatozoa have a greater presence and in‐flow in the ejaculation ducts. The walls are less thick than in the previous phase. The W W is 20.53 ± 2.28 μm. The GSI is 0.21 ± 0.01 g (Figure 2c1).
Spawning phase: All stages of previtellogenesis and vitellogenesis oocytes can be observed simultaneously. The distinctive feature is the presence of postovulatory follicles. Some spaces between lamellae and remnants of final maturation oocytes can occurred. The W W is 50.96 ± 5.57 μm. The GSI is 1.65 ± 0.39 g (Figure 1d1,d2) Final ejaculation sub‐phase: The spermatocytes and spermatids are less abundant in spermatic crypts. The sperm are still abundant in the spermatic crypts and ducts ejaculation. The gonadal wall and stroma are receding and thin. The W W is 30.10 ± 3.88 μm. The GSI is 0.21 ± 0.02 g (Figure 2c2).
Recovering: The previtellogenesis oocytes are present. The distinctive feature is the presence of atresia from mostly vitellogenesis and final maturation oocytes. The postovulatory follicles cannot be identified because they are not the distinctive architecture. The W W is 60.59 ± 3.03 μm. The GSI is 0.99 ± 0.11 g (Figure e1,e2). Post‐ejaculation: Remnants of cell‐stages of spermatogenesis are present in some spermatic crypts. The ejaculation ducts have little number of spermatozoa, not enough to ejaculation. The gonadal wall and stroma begin to be thicker. The W W is 33.48 ± 2.74 μm. The GSI is 0.23 ± 0.05 g (Figure 2d1,d2).
Rest: The ovarian stroma presents thickened connective tissue. The with spaces between the lamellae and oocytes in primary growth can be observed. The ovarian wall is thicker (W W = 64.41 ± 2.04 μɱ) with respect the other ovarian phases. GSI = 0.36 ± 0.04 g (Figure 1f1,f2)
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Note: The data are represented by the mean ± standard deviation.

Abbreviations: D, oocyte diameter; GSI, gonadosomatic index; W W, wall width.

The oogenesis pattern was classified as asynchronous, as more than two oocyte cohorts in different stages were observed simultaneously. Moreover, during the maturity and spawning phases, more than two advanced oocyte stages were observed simultaneously, including vitellogenesis‐III, migratory nucleus and oocyte hydration (Figure 1c1,c2,d1,d2). The spawning pattern was noted as partial, indicating that a female can release multiple batches of oocytes over several days (up to 1 week). This is evident as postovulatory follicles and oocytes in the migratory nucleus and vitellogenesis‐III stages are observed concurrently in the spawning phase.

3.2.2. Spermatogenesis and testicular development in E. labriformis

The data were gathered from 118 testicles and 95 TTs (testicles undergoing a sex‐change process). The inclusion of TTs in this study was due to concurrent spermatogenesis during the sex‐change process. We identified four stages of spermatogenesis: spermatogonia (D = 4.11 ± 0.08 μm), spermatocytes (D = 2.87 ± 0.07 μm), spermatids (D = 2.19 ± 0.03 μm) and spermatozoa (Head D = 1.44 ± 0.02 μm). These cells decrease in size by 65% during spermatogenesis, from spermatogonia to spermatozoa.

The testicular cycle of E. labriformis for spermatozoa production can be described in four TDPs: inactive, development, ejaculation and post‐ejaculation (Table 1) (Figure 2a1,b1,b2,c1,c2,d1,d2). Furthermore, two sub‐phases of the development phase and the ejaculation phase were identified: early development and advanced development, and intensive ejaculation and final ejaculation, respectively. TTs exhibited lower spermatogenesis intensity compared to post‐sex‐change male testicles. However, the accumulation of spermatozoids in the sperm crypts and efferent ducts appears sufficient for successful ejaculation, making them functionally viable (Figure 2e2–e4).

During the testicular function, the testicles decrease in size from GSI = 0.31 ± 0.11 g in the inactive or post‐ejaculation phase to their maximum size of GSI = 0.23 ± 0.01 g during the ejaculation phase. Subsequently, they decrease in size as sperm release concludes and enter the post‐ejaculation phase, at which point the testicular cycle restarts. Testicles in the inactive and early development phases may exhibit a high oocyte coverage (~85–95% in inactive and ~0%–85% in early development) and wall thicknesses of 91.40 ± 36.68 μm and 35.62 ± 3.79 μm, respectively, like the resting ovaries' wall thickness (60.59 ± 3.03 μm) (Figure 2: a1,e1,b1). This suggests that the testicular cycle originates from resting females, skipping the immature phase typically observed in juvenile individuals without prior reproductive experience.

The distribution of spermatogenesis in the lamellae is undelimited, where male and female tissues are intermixed without separation by connective tissue (Figure 2). The spermatogenesis pattern is continuous, enabling the testis to maintain sperm production during periods of release. This indicates that a male can participate in more than one spawning event within a day's spawn.

3.3. Sex‐change process

The sex‐change process was observed in 95 TTs and classified into four distinct stages: 1‐SCS, 2‐SCS, 3‐SCS and 4‐SCS (Table 2). Across these four stages, the gonad undergoes a transition from female tissue (oocytes) to testicular tissue, eventually occupying 100% of the gonadal stroma. The abundance of oocytes decreases during sex change, with vitellogenic oocytes being the first to disappear, while some previtellogenic oocytes persist until the end of the transformation. Moreover, the ovigerous lamellae fuse and tend to show fewer lamellae within the gonadal stroma of testicles, leading to a reduction in the lumen size (Figure 2f1). Simultaneously, the ejaculatory duct forms in the proximal region of each gonadal lobe.

TABLE 2.

Sex‐change stages (SCS) of Ephinephelus labriformis.

Sex‐change stage
1‐SCS The (TTs) presented 117 ± 58 oocytes in previtellogenesis by lamella and some atresia of vitellogenic oocytes (Al = 40 ± 18). The testicular tissue (spermatogonia and spermatocytes) occupies ~5–15% of the lamellae and is distributed in an undefined manner with respect to the female tissue (oocytes) in the stroma of the TTs. The lamellae are observed to have a clear separation between them. The wall of the TT is thick (W W = 91.40 ± 36.68 μm) and the GSI was 0.31 ± 0.10 μm. This stage occurred in individuals with sizes between 20 and 22.5 cm L t (Figures 2e1 and 3).
2‐SCS The TTs presents 79 ± 65 oocytes in previtellogenesis per lamella and Al = 22 ± 17. The sperm crypts are clearly distinguished and may contain all cell stages of spermatogenesis, occupying ~15–30% of the TT stroma. The lamellae are observed with a clear separation between them. The wall of the TT is thick (W W = 58.85 ± 7.91 μm) and the GSI was 0.22 ± 0.057. This stage was observed in individuals with sizes between 21 and 26 cm Lt (Figures 2e2 and 3).
3‐SCS The TTs presents 22 ± 20 oocytes in previtellogenesis per lamellae, and some TT could present Al = 10 ± 7 atresia. The sperm crypts may contain all the cell stages of spermatogenesis, occupying ~30–80% of the TT stroma. The lamellae are observed with a smaller separation between them and some are ~double in width compared to previous SCS, indicating fusion of lamellae. The wall of the TT is slightly less thick (W W = 48.89 ± 6.65 μm) and the GSI was 11 ± 0.015. This SCS occurred in individuals with sizes between 22 and 29 cm L (Figures 2e3 and 3).
4‐SCS The TT presented 3 ± 3 previtellogenesis oocytes per lamellae and they are deteriorated (apoptotic). The sperm crypt occupies ~80%–100% of the TT stroma and may contain all cell stages of spermatogenesis. The lamellae are more compacted between them, with few inter‐lamellae spaces observed. The wall of the TT is thin (W W = 30.14 ± 2.57 μm) and the GSI was 0.23 ± 0.05. This stage was observed in individuals with sizes between 21 and 33.5 cm L t (Figures 2e4 and 3).
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Note: Data are presented as the mean ± standard deviation (μm). GSI, gonadosomatic index; TTs, transformed testicles; Ol, the number of oocytes in one gonadal lamella; Al, the number of atretic oocytes per histological section.

In the 1‐SCS, the TTs do not produce sperm yet and are classified as inactive based on their TDP. Individuals with these testicles are referred to as ITMs (Figure 2a1,a2,e1). Meanwhile, in the 2‐SCS, 3‐SCS and 4‐SCS, the TTs are already producing sperm at different TDPs, concurrent with the sex‐change process (Figure 1e2–e4). These individuals are categorized as ATMs.

3.4. Sexual composition

The sex ratio in the complete fish sample was 1.5 females per male (χ 2 = 19.35, p < 0.001). This result indicates a bias toward a higher number of females in the population. The size intervals in the total sample ranged from 15.5 to 33.5 cm L t and 50 to 615 g W. Specifically, the size ranges for each sexual condition were as follows: 15.5–27.5 cm and 50–355 g for females, 20–23.5 cm and 120–190 g for ITMs, 19–29 cm and 115–380 g for ATMs, and 19–33.5 cm and 110–615 g for males (Figure 4).

FIGURE 4.

FIGURE 4

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Sexual composition of Epinephelus labriformis by size, represented through frequencies (%) of females (white bars), transforming males (light grey) and males (dark grey), as well as the number of females per one male (black dot) and the reference of one male (dotted line). The asterisk (*) indicates statistical differences from a 1:1 sex ratio (p < 0.05).

The sex ratio by size interval revealed a shift in dominance as size increased. Smaller sizes, below 19 cm L t, consisted exclusively of females, while ITMs, ATMs and males were increasingly observed as sizes grew larger (Figures 3 and 4). Larger females were not found at sizes of 27.5 cm L t or larger, only ATMs and males were recorded at these size ranges (Figure 4). A sex ratio of 1:1 was observed only in the size classes of 15.5 cm L t (χ 2 = 2, p = 0.16), 22.5 cm L t (χ 2 = 1.64, p = 0.20) and 23 cm L t (χ 2 = 0.18, p = 0.67) (Figure 4).

FIGURE 3.

FIGURE 3

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Sex‐change stage frequencies per testicular developmental phases (TDPs) and the corresponding total length frequencies (immediate superior figure) with the distinction of the transforming testicles from transformed testicles of Epinephelus labriformis. Sex‐change stages: SCS‐1, SCS‐2, SCS‐3 and SCS‐4.

3.5. Size at sexual maturity

Females: The L m50 was 17.20 cm, the L m60 was 17.50 cm, the L m70 was 17.83 cm, the L m80 was 18.22 cm, the L m90 was 18.80 cm and the L mω was 27.5 cm of L t according to the parameters A = 1.06, B = 110,361 and C = −1.34 (Figure 5). The L mα was 15.50 cm and the larger immature female had a size of 19.50 cm of L t.

FIGURE 5.

FIGURE 5

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Models of population sexual maturity display through size for females and males of Epinephelus labriformis inhabiting Mazatlán bay, Sinaloa, Mexico.

Males: The L m50 was 19.42 cm, the L m60 was 19.65 cm, the L m70 was 19.90 cm, the L m80 was 20.26 cm, the L m 90 was 20.71 cm and the L mω was 33.5 cm of L t according to the parameters A = 0.98, B = 254,604 and C = −1.82 (Figure 5). The L mα was 18.50 cm and the larger inactive male had a size of 23.50 cm of L t.

3.6. Size at sex change

The L c50 was 24.70 cm, the L c60 was 25.21 cm, the L c70 was 25.75 cm, the L c80 was 26.43 cm, the L c90 was 27.50 cm and the L cω was 33.5 cm of L t according to the parameters A = 0.95, B = 1.03 and C = −5.64 (Figure 6). The model was fit from the data obtained from 95 organisms with testicles in the transformation process. The L cα was 20 cm and the largest individual in the process of sex change had a size of 33.5 cm of L t.

FIGURE 6.

FIGURE 6

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Model of population sex‐change displays through size in Epinephelus labriformis inhabiting Mazatlán Bay, Sinaloa, Mexico.

3.7. Hermaphroditism

Previous observations indicate that individuals of E. labriformis initially differentiate and reach sexual maturity as females, followed by a subsequent transition to males. Consequently, all males in our sample are considered secondary males, derived from sexually mature females. This reproductive strategy corresponds to a sexual pattern known as monandric protogynous hermaphroditism. Several key characteristics align with this pattern, as described briefly here.

Hermaphroditism: Individuals undergoing sex change were identified within a size range of 20 to 27.5 cm L t) (Figure 4). Only males were observed in larger class sizes, while smaller class sizes were exclusively occupied by females (Figure 4).

Protogyny: Evidence of protogyny was identified by the presence of sperm crypts within well‐defined ovigerous lamellae (Figure 2e2–e4,f1), as well as atretic oocytes in both previtellogenic and vitellogenic stages within the transforming testicular stroma (Figure 2e2–e4). Remnants of the ovarian lumen were also observed (Figure 2f1). The female‐to‐male ratio was calculated at 1.5:1, with females predominantly found in size classes smaller than 19 cm L t (Figure 4).

Monandria: The gonadal stroma in all individuals displayed well‐defined lamellae in females, lamellae undergoing compaction in individuals transitioning to males (ITMs and ATMs) or compacted lamellae in males (Figure 2e1–e4,f1). Males were observed starting from a size of 20 cm L t, with only males present in size classes greater than 27.5 cm L t (Figure 4). The thickness of the walls of TTs in the inactive TDP phase (early stages of sex change) averaged 91.40 ± 36.68 μm, which is comparable to the wall thickness of ovaries in the resting phase (ODP), suggesting that sex change originates from adult females (Figures 1f1 and 2a2,e1).

4. DISCUSSION

4.1. Gonadal development

The oogenic stages identified in E. labriformis were consistent with those documented for other teleost fishes (Brown‐Peterson et al., 2011; Erisman et al., 2007; Varzzoler, 1996; Wallace & Selman, 1981). We described and defined the developmental phases of gametogenesis based on a number of distinct parameters, including stromal attributes, oocyte diameter, width of the ovarian wall, tissue organization and atresia (West, 1990). The ovarian wall provides a reliable criterion to differentiate between immature and resting females (Ganias et al., 2014) because oocyte stages in both phases are similar to one another (Maldonado‐Amparo et al., 2017). This change in the architecture of the ovarian wall occurs because as the size of the gonad increases through the maturation process, the gonadal wall stretches and expands due to the generation of new connective tissue (Varzzoler, 1996). During gonadal recovery, new connective tissues contract, but are not reabsorbed. This thickening is noticeable in both the walls of the ovary as well as the walls of the gonadal stroma (e.g. lamellae) (Brown‐Peterson et al., 2011; Maldonado‐Amparo et al., 2017; Ruiz‐Ramírez et al., 2018; Varzzoler, 1996; Wallace & Selman, 1981; West, 1990).

Histological evidence indicates that E. labriformis exhibits an asynchronous oogenic pattern and functions as a serial spawner. Females are capable of spawning at least three times in a few days, confirming the species' high reproductive frequency. Post‐ovulatory follicles and oocytes at the migratory nucleus and late vitellogenesis‐III stages were observed contemporaneously during the spawning phase. The three sub‐phases (ejaculation, intensive and final) suggest that males may perform multiple ejaculations during the spawning season. Several reports support that E. labriformis exhibits a haremic mating system in which females mate with multiple males and males, in turn, mate with several females (Adreani et al., 2004; Warner, 1988). This pattern aligns with previous descriptions of opportunistic males (parasitic) present within harems formed by dominant males (Colin, 1992; Erisman & Allen, 2005; Starr et al., 2018; Warner, 1988). Additionally, females can move between harems, allowing their eggs to be fertilized by different males (Kline et al., 2011). The participation of other opportunistic males may result from limited sperm production by a single male, which may be insufficient to fertilize all the eggs released during a spawning season (Coleman et al., 1996; Rhodes & Sadovy, 2002; Sadovy, Colin, & Domeier, 1994; Sadovy, Rosario, & Roman, 1994). This phenomenon of sperm limitation was also evident during the captive spawning of E. labriformis, as evidenced by low fertilization rates. The captive harem consisted of one dominant male and three females, and the presence of an opportunistic male. Under these conditions, a reduction in sperm was evident (unpublished data).

Some differences were identified in the ovarian and testicular developmental phases (ODP and TDP) compared with previously available information on E. labriformis. Several of these differences stem from a previous lack of histological examination (West, 1990), as seen in Hernández‐Flores (2015), where the maturity phase, characterized by the migratory nucleus and hydrated oocyte stages (final oocyte maturation), was not reported. It is important to note that even when histological analyses are performed, final oocyte maturation stages are rarely observed in tropical species because they occur for only a few hours. For example, in serranids such as Paralabrax clathratus, P. maculatofasciatus and P. nebulifer, final oocyte maturation occurs within about 15 h (Oda et al., 1993), typically synchronized with specific phases of the lunar cycle (Takemura et al., 2010). Therefore, monthly sampling must coincide precisely with these short periods to capture final maturation stages. However, in the present study, these stages were successfully recorded thanks to the weekly sampling, which increased the likelihood of detection. Additional differences were found when compared with Ruiz‐Ramírez et al. (2018), who used only four reproductive phases (immature, developing, mature and spawned) and did not distinguish the gonadal reabsorption and resting phases. These latter two phases are essential for understanding the full reproductive cycle and defining the reproductive recrudescence period. Although gonadal development has been described in other protogynous hermaphrodites, such as Hypoplectrodes muccullochi (Webb & Kingsford, 1992), P. maculatofasciatus (Oda et al., 1993), E. guttatus (Sadovy, Rosario, & Roman, 1994), E. rivulatus (Mackei, 2000), E. polyphekadion (Rhodes & Sadovy, 2002), E. fuscoguttatus (Pears et al., 2007) and Cephalopholis panamensis (Erisman et al., 2010), the resting phase has often been omitted or undescribed. This phase, however, is critical because it distinguishes individuals that have already spawned from those maturing for the first time.

4.2. Sex change

Based on histological evidence, 95 individuals were identified as undergoing a sex‐change process, and they were classified into four stages (SCS‐1 to SCS‐4) representing the progressive pathway of this process in E. labriformis. This process involves a gradual loss of ovarian tissue (reduced atresia and previtellogenic oocytes), proliferation of testicular tissue and a transformation of gonadal architecture from a lamellar structure to a compact stroma. These findings agree with the hypothesis of Bruslé and Bruslé (1975) regarding the restructuring and degeneration of tissue of opposite‐sex tissue within Epinephelus species, characterized by the disintegration of ovarian tissue. Similar observations were reported by Kumar‐Bhandari et al. (2003) for Epinephelus merra. Ruiz‐Ramírez et al. (2018) also noted simultaneous oocyte degeneration and spermatogenic tissue in E. labriformis, though without describing the progression of the sex change.

All individuals in the first stage (SCS‐1) showed marked thickening of the width of the ovarian wall, indicating that the sex change begins in resting‐phase females. This thickening likely results from expansion (stretching would make it thinner) during oocyte maturation (Varzzoler, 1996) and subsequent remodelling once reproduction ceases. Thus, all males originate from females that have previously reproduced as females (Bruslé & Bruslé, 1975; Clavijo, 1982; Dipper & Pullin, 1979; Fishelson, 1975; Jones, 1980; Reinboth, 1962; Shapiro & Lubbock, 1980; Warner, 1975). Individuals in SCS‐1 are also considered inactive males (Lluch‐Cota, 1995), exhibiting spermatogonia and spermatocytes in approximately 5%–15% of the lamellae, but without clear sperm production.

In E. labriformis, the gonads rapidly acquire testicular function during sex change, while the resorption of ovarian tissue appears to be gradual and concurrent with spermatogenesis. This gradual transition suggests that remnants of ovarian tissue may persist through more than one reproductive period, as testicular structures observed in the final stage (SCS‐4) correspond to post‐ejaculatory gonads retaining roughly 20% of female‐type stroma. In other tropical fishes, sex change occurs over a short period, typically weeks to months, depending on the species (Gemmell et al., 2019). Consequently, locating transitional individuals in the wild can be challenging (Sadovy & Shapiro, 1987).

During this process, developing testicular tissue intermixes freely with residual ovarian tissue, with no separating membrane or gonadal epithelium, thus forming non‐delimited germinal tissues, as described by Sadovy and Shapiro (1987). This condition is characteristic of several Epinephelids (Kumar‐Bhandari et al., 2003; Ruiz‐Ramírez et al., 2018; Sadovy & Colin, 1995). Moreover, gonadal architecture at the onset of sex change (SCS‐1) retains a lamellar structure typical of females (Sadovy & Shapiro, 1987). As individuals progress through SCS‐2 to SCS‐4, these lamellae coalesce into a single compact mass. Both characteristics, non‐delimited germinal tissue and lamellar compaction, likely enhance sperm storage capacity.

Sex change in Epinephelidae appears to be socially controlled (Coleman et al., 1996; Gemmell et al., 2019; Shapiro, 1981, 1987; Shapiro & Lubbock, 1980; Warner, 1982) and functions to maintain adequate male availability for fertilization and reproductive success (Coleman et al., 1996; Rhodes & Sadovy, 2002; Warner, 1975). Thus, the ability of transitioning gonads to produce sperm rapidly, even before the process is complete, and to utilize lamellar (non‐delimited germinal tissues) enables individuals to exploit favourable spawning conditions (Ferreira, 1995; Mackei, 2000; Rhodes & Sadovy, 2002; Shapiro, 1984; Sadovy & Shapiro, 1987). This physiological flexibility may ensure sperm availability and maximize reproductive output within a limited time frame.

4.3. Sexual composition

The sex ratio of adult E. labriformis (1 male [M]:1.5 females [F]) showed a female‐biased population, a common feature among protogynous hermaphroditism (Sadovy & Shapiro, 1987; Erisman, 2008; Pears et al., 2007; Núñez‐ Díaz, 2016; Hernández‐Flores, 2015; Ruiz‐Ramírez et al., 2018). Others studies have also reported female dominance including 1M:1.7F (Hernández‐Flores (2015), 1M:2.32F in adults from Loreto and Puerto Vallarta, México (Erisman, 2008) and 1M:1.3F in the Bahía de Navidad, Jalisco, Mexico (Ruiz‐Ramírez et al., 2018). Similarly, Núñez‐Díaz (2016) recorded annual sex ratios on the Sinaloa Coast (1M:0.56F in 2012, 1M:1.32F in 2013 and 1M:9.83F in 2015), indicating an apparent trend toward increasing female prevalence over time. At the same time, both mean size (x̄) and the mode (Mo) of captured individuals decreased progressively: x̄ = 22.21 cm and Mo = 22 cm L t in 2012, x̄ = 21.58 cm and Mo = 19.5 cm L t in 2013, and x̄ = 20.7 cm and Mo = 19.5 cm L t in 2015. In the present study, we observed that the proportion of females increased markedly at sizes below 23 cm L t. These differences between studies may reflect variations in the sampled size range, which are often influenced by sampling methods (Sadovy & Shapiro, 1987). In Mazatlan, Sinaloa, fishing gear has remained unchanged in recent years (Núñez‐Díaz, 2016), yet captured fish have become progressively smaller. This likely reflects fishing pressure, where selective removal of larger individuals leads to a reduced number of males in the population (Coleman et al., 1996; Rhodes & Sadovy, 2002; Sadovy, Colin, & Domeier, 1994). Spatial distribution must also be considered as males, particularly among Epinephelids, tend to inhabit deeper habitats than females (Aburto‐Oropeza et al., 2008). However, whether E. labriformis exhibits such vertical segregation remains unknown. The imbalance in sex ratios is a concern for management of protogynous hermaphrodites, such as E. labriformis, as it can strongly influence size at maturity, timing of sex change and male availability. Consequently, reduced abundance may lower fertilization success and sperm capacity, ultimately limiting reproductive output and recruitment (Bannerot, 1987; Coleman et al., 2000; Huntsman et al., 1999; Koenig et al., 1996; Vincent & Sadovy, 1998).

4.4. Size at sexual maturity

The size at sexual maturity for E. labriformis was estimated to be 17.20 cm L t for females and for 19.42 cm L t for males. Núñez‐Díaz (2016) reported a mean maturity size of 17.93 cm L t for both sexes, closely matching the value obtained for females in the present study. Other studies found higher estimates: Hernández‐Flores (2015) reported 20.48 cm L t for females and 22.03 cm L t for males, while Ruiz‐Ramírez et al. (2018) reported maturity sizes for females of 29.6 and 31.3 cm L t for males. Apparent reduction in size at sexual maturity over time should be interpreted cautiously, as methodological biases limit direct comparison. Nuñez‐Díaz (2016) applied an indirect approach using the empirical equation of Froese and Binohlan (2000). In contrast, Hernández‐Flores (2015) and Ruiz‐Ramírez et al. (2018) employed logistic models derived from direct observations of gonadal histology, as we did in the present study. However, Hernández‐Flores (2015) used a macroscopic technique, based on gonadal appearance, which can be unreliable due to the uncertain morphochromatic distinction between the immature and resting phases. To fit their model, only cumulative frequencies of adults in developmental, mature and post‐spawning phases were used, resulting in overestimation relative to the findings presented here. Subsequent observations, together with the similarity in gonadal architecture between sexes observed here, indicate that distinguishing sex during reproductive inactivity based solely on appearance remains unreliable (Núñez‐Díaz, 2016). Ruiz‐Ramírez et al. (2018) by contrast, applied histological diagnosis, a more precise method than macroscopic analysis (West, 1990) and used a frequency estimator for size similar to that in the present study. Nevertheless, their estimates correspond to a different population inhabiting the coasts of Jalisco and on the southern Gulf of California (Ruiz‐Ramírez et al., 2018). These differences in size at maturity may reflect ecological and population‐level variability. Additionally, the selection of larger individuals, typically males in protogynous species, imposes evolutionary pressure favouring earlier maturation and sex change at smaller sizes (Bannerot, 1987; Koenig et al., 1996; Vincent & Sadovy, 1998; Huntsman et al., 1999; Coleman et al., 2000 in Rhodes & Sadovy, 2002). According to local fishers from Playa Norte, E. labriformis populations along the Mazatlan coast have been abundant but heavily exploited for more than two decades. Although our study did not aim to test this hypothesis, causality cannot be confirmed; size‐selective harvest may promote earlier maturation at smaller sizes in protogynous species.

4.5. Size at sex change

Sex change in E. labriformis occurs between 20 and 27.5 cm L t, with an estimated L c50 of 24.7 cm L t representing 50% of transitional individuals in the population. Despite the methodological and latitudinal sampling differences (Nayarit and Jalisco), the reported size range for sex change overlaps with those observed in the present study. On the Nayarit coast, Hernández‐Flores (2015) suggested that sex change occurs between 24 and 26 cm L t based on the sex ratio by size, whereas Núñez‐Díaz (2016) estimated a range of 17–20.7 cm L t using histological confirmation of actively developing males (active spermatogenesis and available sperm). In contrast, along the Mazatlan coast, we observed previtellogenic oocytes in individuals of comparable sizes. On the Jalisco coast, Ruiz‐Ramírez et al. (2018) found that the smallest transitional individuals at 26 cm L t, marking the onset of sex change, which continued up to 36 cm L t. This finding was supported by histological analysis of 33 individuals identified as undergoing sex change. These observations suggest that the sex change in the Mazatlan Bay populations begins at smaller sizes compared to the Jalisco coast. We propose that these differences likely result from local environmental factors, social structure and fishing pressure between regions.

4.6. Monandric protogynous hermaphroditism

Protogynous hermaphroditism is a common sexual pattern among members of the Epinephelidae family, including E. adscensionis (Kline et al., 2011), E. aeneus (Bruslé y Bruslé 1975), E. drummondhayi (Brulé et al., 2000), E. fuscoguttatus (Pears et al., 2007), E. guttatus (Sadovy, Rosario, & Roman, 1994), E. aeneus and E. guaza (Bruslé y Bruslé, 1975), E. morio (Brulé et al., 1999; Moe, 1969), E. rivulatus (Mackei, 2000), Hyporthodus quernus (De Martini et al., 2011), Plectropomus leopardus (Ferreira, 1995) and E. labriformis (Ruiz‐Ramírez et al., 2018). Monandry within protogynous hermaphrodites, where males are derived exclusively from females, is frequent in the Epinephelinae. However, confirming this sexual pattern often depends on the quality and type of evidence available, and few cases have been rigorously validated. The present study provides detailed histological and population‐level evidence describing the sex‐change process and sex composition by size, confirming that E. labriformis exhibits monandric protogynous hermaphroditism.

Various criteria have been proposed for theoretically diagnosing protogynous hermaphroditism in fishes (Sadovy & Shapiro, 1987), including a mathematical approach (Warner, 1975) and histological approaches (Sadovy & Shapiro, 1987). The latter relies on indicators such as membrane‐lined cavities within testes, transitional individuals, atretic oocytes (stages 1–3) within testicular tissue, sperm sinuses in the gonadal wall and population size structure (Brulé et al., 1999; Oda et al., 1993; Pears et al., 2007; Rhodes & Sadovy, 2002; Sadovy & Shapiro, 1987; Webb & Kingsford, 1992). In E. labriformis, we observed sperm crypts within well‐defined ovigerous lamellae, atretic oocytes in previtellogenic and vitellogenic stages embedded in transforming testicular stroma and remnants of the ovarian lumen. The female‐to‐male ratio was 1.5:1 and all individuals smaller than 19 cm L t were female. Notably, 95 transitional individuals were identified, including inactive males with thickened ovarian walls, revealing a sequence of sexual transition involving degeneration of ovarian tissue and proliferation of testicular tissue. The initial ovarian tissue disappeared following sex reversal, but the testes retained the ovarian lumen and lamellar ovarian configuration (Sadovy & Shapiro, 1987). The presence of an ovarian lumen within a testis provides strong evidence of previous female function (Reinboth, 1980). Additionally, newly formed spermatic crypts were found in female‐derived males (Sadovy & Shapiro, 1987). In E. labriformis, gonadal stroma in all individuals consisted of well‐defined lamellae: females exhibited lamellar structures, transitional individuals (ITMs and ATMs) displayed partial compaction and males presented compacted lamellae. Males appeared from 19 cm L t onward, with only males found above 28 cm L t. The wall thickness of all TTs in inactive TDP, representing early stages of sex change, averaged 91.40 ± 36.68 μm, similar to that of ovaries in resting phase (ODP), suggesting that sex change originates from adult females. Histological evidence further indicates that the sex change occurs after a resting phase: the female gonad transitions to an inactive male gonad containing previtellogenic oocytes, followed by spermatids and spermatocytes (Lluch‐Cota, 1995; Reinboth, 1980; Sadovy & Shapiro, 1987). Given the year‐long weekly sampling and the high proportion (18%) of transitional individuals observed, these findings are considered robust, therefore we conclude that E. labriformis exhibits monandric protogynous hermaphroditism along the Mazatlan, Sinaloa coast, Mexico.

5. CONCLUSION

Gonadal development in E. labriformis parallels that of other teleost fishes, particularly in the use of stromal attributes, oocyte diameter measurements and ovarian wall characteristics to distinguish immature from resting females. The asynchronous oocyte production and partial spawning pattern indicate a polygynous mating system, characterized by a haremic structure. Four distinct stages of sex change were identified based on histological evidence, revealing a gradual loss of ovarian tissue, proliferation of testicular tissue and major transformations in gonadal architecture. The process begins in females during the resting ovarian phase, with males arising from females that have previously spawned. The natural population of E. labriformis is female‐biased, consistent with the reproductive strategy of protogynous hermaphrodites. The estimated size at sexual maturity (17.2 cm L t) and of males (19.4 cm L t) differs from previous reports, likely due to methodological differences among studies and sampling of different regional populations. The observed size range for sex change was 20–27.5 cm L t, with an estimated 50% transition (L c50) occurring at 24.7 cm L t. This study confirms that E. labriformis exhibits monandric protogynous hermaphroditism, where some males are classified as secondary males. Currently, Mexico lacks fishing regulations defining a minimum catch size or a seasonal closure for E. labriformis. Based on our present findings, we recommend establishing a minimum catch size between 24 and 27 cm L t to protect smaller females and larger males, thereby maintaining a balanced breeding sex ratio. Furthermore, implementing a closed fishing season during the reproductive period would promote successful spawning and enhance the sustainability of the species' population structure.

AUTHOR CONTRIBUTIONS

S.C.R.: Sample processing, writing and draft revision. L.C.J.: Sample processing, writing and draft revision. M.B.J.M.: Sampling design and draft review. M.L.A.: Field sampling, sample collection and draft review. M.M.R.: Financial support, field sampling and draft review. I.C.L.: Sampling design, writing and draft revision.

ACKNOWLEDGEMENTS

We sincerely thank the staff of the marine fish hatchery at CIAD, A.C., for their assistance in transporting the fish, as well as the Fisheries Ecology Laboratory and the Histology Laboratory of the Faculty of Marine Sciences of the University of Sinaloa for their valuable technical support throughout this project. We also acknowledge the Mexican Institute for Research in Sustainable Fisheries and Aquaculture (IMIPAS) for its collaboration and institutional support. Finally, we thank Mark Q. Martindale for his valuable assistance in editing the manuscript.

REFERENCES

  1. Aburto‐Oropeza, O. , Erisman, B. E. , Valdez‐Ornelas, C. , & Danemann, G. D. (2008). Serránidos de importancia comercial del Golfo de California: Ecología, pesquerías y conservación. ResearchGate. https://www.researchgate.net/publication/281333378
  2. Adreani, M. S. , Erisman, B. , & Warner, R. R. (2004). Courtship and spawning behavior in the California Sheephead, Semicossyphus pulcher (Pisces: Labridae). Environmental Biology of Fishes, 71(1), 13–19. 10.1023/b:ebfi.0000043177.98895.f7 [DOI] [Google Scholar]
  3. Baca‐Hovey, C. , Allen, L. G. , & Hovey, T. E. (2002). The reproductive pattern of barred sand bass (Paralabrax nebulifer) from southern California (pp. 164–169). California Cooperative Oceanic Fisheries Investigations Reports. http://www.calcofi.org/publications/calcofireports/v43/Vol_43_Baca-Hovey_etal.pdf [Google Scholar]
  4. Baldor, V. A. (2019). Geometría y Trigonometría 4A. Grupo editorial Patria. [Google Scholar]
  5. Bancroft, J. D. , & Gamble, M. (2013). Theory and practice of histological techniques. Churchill Livingstone/Elsevier. [Google Scholar]
  6. Bannerot, S. P. (1987). Reproductive strategies and the management of snapper and groupers in the Gulf of Mexico and Caribbean.
  7. Binohlan, C. (1998). The maturity table. In Froese R. & Pauly D. (Eds.), FishBase 98: Concepts, design and data sources (pp. 176–179). ICLARM. [Google Scholar]
  8. Brown‐Peterson, N. J. , Wyanski, D. M. , Saborido‐Rey, F. , Macewic, B. J. , & Lowerre‐Barbieri, S. K. (2011). A standardized terminology for describing reproductive development in fishes. Marine and Coastal Fisheries, 3(1), 52–70. 10.1080/19425120.2011.555724. [DOI] [Google Scholar]
  9. Brulé, T. , Colas‐Marrufo, T. , Tuz‐Sulub, A. , & Déniel, C. (2000). Evidence for protogynous hermaphroditism in the serranid fish Epinephelus drummondhayi (Perciformes: Serranidae) from the Campeche Bank in the southern Gulf of Mexico. Bulletin of Marine Science, 66(2), 513–521. [Google Scholar]
  10. Brulé, T. , Déniel, C. , Colas‐Marrufo, T. , & Sánchez‐Crespo, M. (1999). Red grouper reproduction in the southern Gulf of Mexico. Transactions of the American Fisheries Society, 128(3), 385–402. [Google Scholar]
  11. Bruslé, J. , & Bruslé, S. (1975). Ovarian and testicular intersexuality in two Protogynous Mediterranean groupers, Epinephelus aeneus and Epinephelus guaza . In Reinboth R. (Ed.), Intersexuality in the animal kingdom (pp. 222–227). Springer‐Verlag. 10.1007/978-3-642-66069-6_21 [DOI] [Google Scholar]
  12. Buesa, R. J. , & Peshkov, M. V. (2009). Histology without xylene. Annals of Diagnostic Pathology, 13(4), 246–256. [DOI] [PubMed] [Google Scholar]
  13. Clavijo, I. (1982). Aspects of the reproductive biology of the redband parrotfish Sparisoma aurofrenatum, (Doctoral thesis, University of Puerto Rico, Mayaguez, Puerto Rico).
  14. Coleman, F. C. , Koenig, C. C. , & Collins, A. L. (1996). Reproductive styles of shallow‐water groupers (Pisces: Serranidae) in the eastern gulf of México and the consequences of fishing spawning aggregations. Environmental Biology of Fishes, 47, 129–141. [Google Scholar]
  15. Coleman, F. C. , Koenig, C. C. , Huntsman, G. R. , Musick, J. A. , Eklund, A. M. , McGovern, J. C. , Chapman, R. W. , Sedberry, G. R. , & Grimes, C. B. (2000). Long‐lived reef fishes: The grouper‐snapper complex. Fisheries, 25(3), 14–21. [Google Scholar]
  16. Colin, P. L. (1992). Preliminary investigation of reproductive activity of the jewfish, Epinephelus itajara (Pisces: Serranidae). In Goodwin M. H. & Waugh G. T. (Eds.), Proceedings of 43rd Gulf and Caribbean Fisheries Institute(Vol. 43, pp. 138–147). Gulf and Caribbean Fisheries Institute. [Google Scholar]
  17. De Martini, E. E. , Everson, A. R. , & Nichols, R. S. (2011). Estimates of body sizes at maturation and at sex change, and the spawning seasonality and sex ratio of the endemic Hawaiian grouper (Hyporthodus quernus, F. Epinephelidae). Fishery Bulletin, 109(1), 123–134. [Google Scholar]
  18. Del Moral‐Flores, L. (2007). Contribución al conocimiento de la biología de la cabrilla verde Epinephelus labriformis (Jenys, 1840), dentro de la pesca artesanal en la playa Norte de Mazatlán, Sinaloa (Tesis licenciatura). Disponible en Biblioteca de la Universidad Autónoma de Sinaloa, Mazatlán, Sinaloa, Mexico, 81 pages.
  19. Devlaming, V. , Grossman, G. D. , & Chapman, F. (1982). On the use of the gonadosomatic index. Comparative Biochemistry and Physiology Part A Physiology, 73(1), 31–39. [Google Scholar]
  20. Dipper, F. A. , & Pullin, R. S. V. (1979). Gonochorism and sex‐inversion in British Labridae (Pisces). Journal of Zoology, 187, 97–112. [Google Scholar]
  21. Erisman, B. E. (2008). Reproductive biology and evolution of Epinephelid and Serranid fishes (Perciformes, Epinephelidae, Serranidae. (Doctoral thesis, University of California, USA). Retrieved from https://escholarship.org/content/qt8k74w8x9/qt8k74w8x9.pdf?t=lqhktv
  22. Erisman, B. E. , & Allen, L. G. (2005). Color patterns and associated behaviors in the kelp bass, Paralabrax clathratus (Teleostei: Serranidae). Bulletin ‐ Southern California Academy of Sciences, 104(2), 45–62. 10.3160/0038-3872(2005)104[45:CPAABI]2.0.CO;2 [DOI] [Google Scholar]
  23. Erisman, B. E. , Buckhorn, M. L. , & Hastings, P. A. (2007). Spawning patterns in the leopard grouper, Mycteroperca rosacea, in comparison with other aggregating groupers. Marine Biology, 151, 1849–1861. [Google Scholar]
  24. Erisman, B. E. , Craig, M. T. , & Hastings, P. A. (2010). Reproductive biology of the Panama graysby Cephalopholis panamensis (Teleostei: Epinephelidae). Journal of Fish Biology, 76, 1312–1328. 10.1111/j.1095-8649.2010.02567.x [DOI] [PubMed] [Google Scholar]
  25. Estrada‐Godínez, J. A. , Maldonado‐García, M. , Gracia‐López, V. , & Carrillo, M. (2011). Ciclo reproductivo de la cabrilla sardinera Mycteroperca rosacea en la bahía de La Paz, México. Ciencias Marinas, 37(4), 425–441. [Google Scholar]
  26. Ferreira, B. P. (1995). Reproduction of the common coral trout Plectropomus leopardus (Serranidae: Epinephelinae) from the central and northern great barrier reef, Australia. Bulletin of Marine Science, 56(2), 653–669. [Google Scholar]
  27. Fishelson, L. (1975). Ecology and physiology of sex reversal in Anthias squamipinnis (Peters) (Teleostei: Anthiidae). In Reinboth R. (Ed.), Intersexuality in the animal kingdom (pp. 284–294). Springer‐Verlag. [Google Scholar]
  28. Fricke, R. , Eschmeyer, W. N. , & Van der Laan, R. (2025). Eschmeyer's Catalog of Fishes: Genera, species, references. California Academy of Sciences. (https://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp). Electronic version accessed 09/04/2025 [Google Scholar]
  29. Froese, R. , & Binohlan, C. (2000). Empirical relationships to estimate asymptotic length, length at first maturity and length at maximum yield per recruit in fishes, with a simple method to evaluate length frequency data. Journal of Fish Biology, 56, 758–773. 10.1111/j.1095-8649.2000.tb00870.x [DOI] [Google Scholar]
  30. Froese, R. , & Pauly, D. (2025). FishBase. World Wide Electronic Publication. https://www.fishbase.org [Google Scholar]
  31. Ganias, K. , Murua, H. , Claramunt, G. , Dominguez‐Petit, R. , Gonçalves, P. , Juanes, F. , Keneddy, J. , Klibansky, N. , Korta, M. , Kurita, Y. , Lowerre‐Barbieri, S. , Macchi, G. , Matsuyama, M. , Medina, A. , Nunes, C. , Plaza, G. , Rideout, R. , Somarakis, S. , Thorsen, A. , … Yoneda, M. (2014). Chapter 4: Egg production. In Domínguez‐Petit R., Marua H., Saborido‐Rey F., & Trippel E. (Eds.), Handbook of applied fisheries reproductive biology for stock assessment and management (pp. 5–110). http://hdl.handle.net/10261/87768). Digital CSIC. [Google Scholar]
  32. Gemmell, J. N. , Told, V. E. , Goikoetxea, A. , Ortega‐Recalde, O. , & Hore, A. T. (2019). Natural sex change in fish. Current Topics in Developmental Biology, 134, 1–47. [DOI] [PubMed] [Google Scholar]
  33. Hernández‐Flores, E. (2015). Aspectos biológicos de la cabrilla verde Epinephelus labriformis (Jenyns, 1840) capturadas por la pesquería de playa Norte Mazatlán (Tesis de licenciatura). Disponible en la Universidad Autónoma de Sinaloa, México.
  34. Humason, G. L. (1979). Animal Tissue Techniques (4th ed.). W. H. Freeman Co. [Google Scholar]
  35. Huntsman, G. R. , Potts, J. , Mays, R. W. , & Vaughan, D. (1999). Groupers (Serranidae, Epinephelinae): Endangered apex predators of reef communities. American Fisheries Society, 23, 217–231. [Google Scholar]
  36. Jones, G. P. (1980). Growth and reproduction in the protogynous hermaphrodite Pseudolabrus celidotus (Pisces: Labridae) in New Zealand. American Society of Ichthyologists and Herpetologists, 4, 660–675. [Google Scholar]
  37. Kline, R. J. , Khan, I. A. , & Holt, G. J. (2011). Behavior, color change and time for sexual inversion in the Protogynous grouper (Epinephelus adscensionis). PLoS One, 6(5), 1–8. 10.1371/journal.pone.0019576 [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Koenig, C. C. , Coleman, F. C. , Collins, L. A. , Sadovy, Y. , & Colin, P. L. (1996). Reproduction in gag (Mycteroperca microlepis) (Pisces: Serranidae) in the eastern Gulf of Mexico and the consequences of fishing spawning aggregations. In Arreguín‐Sánchez F., Mundo J. L., Balgos M. C., & Pauly D. (Eds.), Biology, fisheries and culture of tropical groupers and snappers (pp. 307–323). International Center for Living Aquatic Resources Management. [Google Scholar]
  39. Kumar‐Bhandari, R. , Komuro, H. , Nakamura, S. , Higa, M. , & Nakamura, M. (2003). Gonadal restructuring and correlative steroid hormone profiles during natural sex change in Protogynous honeycomb grouper (Epinephelus merra). Zoological Science, 20, 1399–1404. [DOI] [PubMed] [Google Scholar]
  40. Lluch‐Cota, D. B. (1995). Aspectos reproductivos de la cabrilla arenera, Paralabrax maculatofascíafus (Pisces:Serranidae) en Bahía Magdalena‐Almejas, Baja California Sur, México (tesis de maestría, CICIMAR‐IPN, México). Disponible en Repositorio Digital IPN. http://www.repositoriodigital.ipn.mx/handle/123456789/15220
  41. Mackei, M. (2000). Reproductive biology of the halfmoon grouper, Epinephelus rivulatus, at Ningaloo reef, Western Australia. Environmental Biology of Fishes, 57, 363–376. [Google Scholar]
  42. Maldonado‐Amparo, M. A. , Sánchez‐Cárdenas, R. , Salcido‐Guevara, L. A. , & Ramírez‐Pérez, J. S. (2017). Gonadal development of Peprilus medius (Peters, 1869) (Perciformes: Stromateidae) from southeast of the Gulf of California, México. International Journal of Morphology, 35(1), 56–61. [Google Scholar]
  43. Márquez‐Cuétara, A. (2018). Ciclo reproductivo, fecundidad parcial y patrón sexual de Cephalopholis colonus (Teleostei: Serranidae) en el sudoeste del Golfo de California (tesis de maestría, CICIMAR‐IPN, México). Obtenido en. https://www.vliz.be/imisdocs/publications/320278.pdf
  44. Moe, M. A. (1969). Biology of the red grouper Epinephelus morio (Valenciennes) from the eastern Gulf of Mexico (Professional Papers Series, Florida Department of Natural Resources, Marine Research Laboratory, USA). Retrieved for https://www.researchgate.net/publication/34157325
  45. Núñez‐Díaz, A. (2016). Interanualidad en la estructura poblacional de la cabrilla verde Epinephelus labriformis (JENYNS, 1840) en la pesquería de Playa Norte, Mazatlán, México (Tesis de licenciatura, Universidad Autónoma de Sinaloa, México).
  46. Oda, L. D. , Lavenberg, R. J. , & Rounds, J. M. (1993). Reproductive biology of Paralabrax (Pisces: Serranidae). California Cooperative Oceanic Fisheries Investigations Reports, 34, 122–132. [Google Scholar]
  47. Pears, R. J. , Choat, J. H. , Mapstone, B. D. , & Beggs, G. A. (2007). Reproductive biology of a large, aggregation‐spawning serranid, Epinephelus fuscoguttatus (Forsska°l): Management implications. Journal of Fish Biology, 71, 795–817. 10.1111/j.1095-8649.2007.01545.x [DOI] [Google Scholar]
  48. Pla, S. , Benvenuto, C. , Capellini, I. , & Piferrer, F. (2022). Switches, stability and reversals in the evolutionary history of sexual systems in fish. Nature Communications, 13, 1–13. [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Raymundo‐Huizar, A. R. (2016). Hábitos alimentarios de Epinephelus labriformis en las Islas Marietas, Nayarit, México. Acta pesquera. Diciembre, 2019. Sitio web: http://www.enip.com.mx/ap7_3.pdf
  50. Reinboth, R. (1962). Morphologische und funktionelle zweigeschlechtigkeit bei marinen teleostiern (Serranidae, Sparidae, Centracanthidae and Labridae). Zoologische Jahrbücher. Abteilung für Allgemeine Zoologie Und Physiologie der Tiere, 69, 405–480. [Google Scholar]
  51. Reinboth, R. (1980). Can sex inversion be environmentally induced? Biology of Reproduction, 22, 49–59. [DOI] [PubMed] [Google Scholar]
  52. Rhodes, K. L. , & Sadovy, Y. (2002). Reproduction in the camouflage grouper (Pisces: Serranidae) in Pohnpei Federated States of Micronesia. Bulletin of Marine Science, 70(3), 851–869. [Google Scholar]
  53. Robertson, D. R. , & Allen, G. R. (2015). Peces Costeros del Pacífico Oriental Tropical. Instituto Smithsonian de investigaciones Tropicales. [Google Scholar]
  54. Robertson, D. R. , & Allen, G. R. (2024). Shorefishes of the Tropical Eastern Pacific: online information system. Version 3.0 Smithsonian Tropical Research Institute, Balboa, Panamá.
  55. Ruiz‐Ramírez, S. , Pérez‐Segoviano, M. A. , Lucano‐Ramírez, G. , Gonzales‐Sansón, G. , Aguilar‐Betancourt, G. , & Flores‐Ortega, J. R. (2018). Reproducción de la cabrilla pinta Epinephelus labriformis en la Bahía de Navidad, Jalisco, México. Revista de Biología Marina y Oceanografía, 53(3), 335–347. 10.22370/rbmo.2018.53.3.1358 [DOI] [Google Scholar]
  56. Sadovy, Y. , & Colin, P. L. (1995). Sexual development and sexuality in Nassau grouper. Journal of Fish Biology, 46, 961–976. [Google Scholar]
  57. Sadovy, Y. , Colin, P. L. , & Domeier, M. L. (1994a). Aggregation and spawning in the tiger grouper, Myteroperca tigris (Pisces: Serranidae). American Society of Ichthyologists and Herpetologists, 2, 511–516. [Google Scholar]
  58. Sadovy, Y. , & Liu, M. (2008). Functional hermaphroditism in teleosts. Fish and Fisheries, 9, 1–41. [Google Scholar]
  59. Sadovy, Y. , Rosario, A. , & Roman, A. (1994b). Reproduction in an aggregating grouper, the red hind, Epinephelus guttatus . Environmental Biology of Fishes, 41, 269–286. [Google Scholar]
  60. Sadovy, Y. , & Shapiro, D. Y. (1987). Criteria for the diagnosis of hermaphroditism in fishes. American Society of Ichthyologists and Herpetologists, 1, 136–156. [Google Scholar]
  61. Schulz, R. W. , De Franca, L. R. , Jacques‐Lareyre, J. , LeGac, F. , Chiarini‐Gracia, H. , Nobrega, R. E. , & Miura, T. (2010). Spermatogenesis in fish. General and Comparative Endocrinology, 165, 390–411. 10.1016/j.ygcen.2009.02.013 [DOI] [PubMed] [Google Scholar]
  62. Shapiro, D. Y. (1981). Size, maturation, and the social control of sex reversal in the coral reef fish Anthias squamipinnis (Peters). Journal Zoological London, 193, 105–128. 10.1111/j.1469-7998.1981.tb01494.x [DOI] [Google Scholar]
  63. Shapiro, D. Y. (1984). Sex reversal and sociodemographic processes in coral reef fishes. In Potts G. W. & Wooton R. J. (Eds.), Fish reproduction strategies and tactics (pp. 103–118). Academic Press. [Google Scholar]
  64. Shapiro, D. Y. (1987). Differentiation and evolution of sex change in fishes. Bioscience, 37(7), 490–497. [Google Scholar]
  65. Shapiro, D. Y. , & Lubbock, R. (1980). Group sex ratio and sex reversal. Journal of Theoretical Biology, 82, 411–426. [DOI] [PubMed] [Google Scholar]
  66. Siegel, V. , & Loeb, V. (1994). Length and age at maturity of Antarctic krill. Antarctic Science, 6(4), 479–482. [Google Scholar]
  67. Smith, C. L. (1965). The patterns of sexuality and classification of serranid fishes. American Museum Novitates, 2207, 1–20. [Google Scholar]
  68. Somerton, D. A. (1980). A computer technique for estimating the size of sexual maturity in crabs. Canadian Journal of Fisheries and Aquatic Sciences, 47, 1488–1494. [Google Scholar]
  69. Starr, R. M. , Ballesteros, E. , Sala, E. , & Llenas, J. M. (2018). Spawning behavior of the tiger grouper (Mycteroperca tigris) in a Caribbean atoll. Environmental Biology of Fishes, 101, 1641–1655. 10.1007/s10641-018-0813-4 [DOI] [Google Scholar]
  70. Takemura, A. , Rahman, M. S. , & Park, Y. J. (2010). External and internal controls of lunar‐related reproductive rhythms in fishes. Journal of Fish Biology, 76(1), 7–26. 10.1111/j.1095-8649.2009.02481.x [DOI] [PubMed] [Google Scholar]
  71. Varzzoler, M. A. (1996). Desenvolvimiento ovariano. In En Varzzoler M. A. (Ed.), Biologia da reprodução de peixes teleósteos: teoria e prática (pp. 48–57). Editora da Universidade Estadual de Maringá. [Google Scholar]
  72. Vincent, A. C. J. , & Sadovy, Y. (1998). Reproductive ecology in the conservation and management of fishes. In Caro T. (Ed.), Behavioural ecology and conservation biology (pp. 209–245). Oxford University Press. [Google Scholar]
  73. Wallace, R. A. , & Selman, K. (1981). Cellular and dynamic aspects of oocyte growth in teleosts. American Zoologist, 21, 325–343. [Google Scholar]
  74. Warner, R. R. (1975). The adaptive significance of sequential hermaphroditism in 109 animals. American Naturalist, 109, 61–82. [Google Scholar]
  75. Warner, R. R. (1988). Sex change in fishes: Hypotheses, evidence, and objections. Environmental Biology of Fishes, 22, 81–90. [Google Scholar]
  76. Warner, R. R. (1982). Mating systems sex change and sexual demography in the rainbow wrasse, Thalassoma lucasanum . American Society of Ichthyologist and Herpetologists, 3, 653–660. [Google Scholar]
  77. Webb, R. O. , & Kingsford, M. J. (1992). Protogynous hermaphroditism in the halfbanded sea perch, Hypoplectrodes maccullochi (Serranidae). Journal of Fish Biology, 40, 951–961. 10.1111/j.1095-8649.1992.tb02640.x [DOI] [Google Scholar]
  78. West, G. (1990). Methods of assessing ovarian development in fishes: A review. Australian Journal of Marine and Freshwater Research, 41, 199–222. [Google Scholar]
  79. Zar, J. H. (2010). Biostatistical analysis. Prentice Hall. [Google Scholar]

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