Data on the diet composition of Hippocampus guttulatus cuvier, 1829: Different prey preferences among habitats

Abstract

The data presented here support research article entitled ‘Trophic flexibility and prey selection of the wild long-snouted seahorse Hippocampus guttulatus Cuvier, 1829 in three coastal habitats’’ Ape et al., 2019. Determinations of the dietary composition, differences in prey selection and potential prey abundance and availability among three habitats at Taranto Mar Piccolo were based on the analysis of gut contents of seahorses and sediment samples. Both highly (Corallina elongata and Cladophora prolifera) and low complex (sandy bottom) habitats were investigated. Prey items were divided into two size classes: <1 mm and >1mm. Data about the total abundance of each prey size class in gut contents and sediments in three different habitats and PERMANOVA comparisons are given.

Specifications table

Subject area	Ecology
More specific subject area	Dietary and foraging ecology
Type of data	Tables
How data was acquired	Gut contents of seahorses were obtained by flushing method, while sediments used for the study of benthic fauna were manually sampled by three replicate cores. Organisms were counted and classified at the major taxa level of taxonomic discrimination using a stereomicroscope (after extraction from sediments and algal fragments in case of benthic organisms). Statistical analyses were performed using PRIMER v6 + software.
Data format	Raw and analyzed
Experimental factors	Gut contents of 83 individuals of Hippocampus guttulatus and samples of benthic fauna from three different habitats at Taranto Mar Piccolo were analyzed.
Experimental features	Taxonomical identification of the ingested prey from gut contents and potential prey from benthic faunal samples to determine diet of H. guttulatus and investigate the differences in the diet composition respect to the prey availability in different habitats.
Data source location	Taranto Mar Piccolo, Southern Italy
Data accessibility	Data are included in this article
Related research article	F. Ape, G. Corriero, S. Mirto, C. Pierri, T. Lazic, M. Gristina. Trophic flexibility and prey selection of the wild long-snouted seahorse Hippocampus guttulatus Cuvier, 1829 in three coastal habitats. Estuar. Coast. Shelf Sci., 224, 2019, 1–10.

Value of the data •The presented data show that gut content analysis is a valuable tool to determine the dietary composition of seahorses. Obtained dietary information can be used by other researchers. •Data enabled the determination of the dietary composition of long-snouted seahorses as well as differences in the prey preferences among investigated habitats. •Flushing method, adopted by this work and used to sample gut contents, allowed to appreciate the importance of prey without calcareous/chitinous exoskeleton, such as nematodes. •Overall, collected data could help to understand the variability and consistency of ecological requests of this species and could help to comprehend better the patchy distribution of seahorses.

1. Data

Data presented describe investigated habitats (Corallina elongata, sandy bottom and Cladophora prolifera; Table 1), total abundance of prey items found in seahorse gut contents and in sediments of each habitat (Table 2). In Table 3, Table 4, the results of PERMANOVA analyses, performed to establish differences in the diet among three habitats in terms of total abundance, abundance of the different size classes (<1mm, > 1mm), taxa richness and composition of prey, are reported. Finally, PERMANOVA analyses, carried out to determine the differences in total abundance of benthic fauna, abundance of different size classes (<1mm, > 1mm), taxa richness and community composition among investigated habitats, are presented in Table 5, Table 6.

Table 1.

Descriptions, extensions (m²) and depth ranges (m) of the sampled habitat types (Corallina elongata, sandy bottom and Cladophora prolifera).

Habitat	Description	Surface (m2)	Depth range (m)
Corallina elongata	Corallina elongata forms a dense turf on the vertical side of the concrete wall. The algal turf, interrupted by brown algae (Cystoseira sp., Dictyota dichotoma) and filter feeders (large sabellids, both colonial and solitary ascidians, demosponges, bryozoans and hydrozoans), provides substratum and refuges for diverse epifaunal organisms.	5.504	0.4–0.7
Soft bottoms	Near the coastline, soft bottoms are mixed with a large amount of organogenous concretions (bivalve and gastropods shells), small stones and artificial hard substrates that are mainly colonized by sabellids and solitary ascidians.	4.419	1.6–2.2
Cladophora prolifera	Large beds interspersed with soft bottom. Sabellid polychaetes, solitary and colonial ascidians are scattered on the substrate. Ceriantharia Pachycerianthus solitarius may be locally abundant.	7.471	3.3–3.9

Table 2.

Abundance (N = mean ± standard deviation) of each size class of organisms found in the guts of H. guttulatus and in the sediments in three different habitats (Corallina elongata, sandy bottom and Cladophora prolifera). Data on the total abundance (sum of organisms < 1mm and > 1mm) of organisms found in the guts and sediments in three habitats are published in Table 1, Table 3, respectively, of the article: Trophic flexibility and prey selection of the wild long-snouted seahorse Hippocampus guttulatus Cuvier, 1829 in three coastal habitats [1].

Taxa	Corallina elongata				Sandy bottom				Cladophora prolifera
	Gut content		Sediment content		Gut content		Sediment content		Gut content		Sediment content
	<1mm	>1mm	<1mm	>1mm	<1mm	>1mm	<1mm	>1mm	<1mm	>1mm	<1mm	>1mm
Nematoda	12.4 ± 8.9	0.0	790.0 ± 388.0	0.0	5.0 ± 8.0	0.0	122.0 ± 13.5	0.0	4.0 ± 3.5	0.0	92.3 ± 11.0	0.0
Copepoda	14.5 ± 10.0	0.0	398.5 ± 78.5	0.0	4.1 ± 3.3	0.0	403.0 ± 136.8	0.0	8.7 ± 5.8	0.0	262.0 ± 73.0	0.0
Harpacticoida	12.2 ± 8.4	0.0	322.0 ± 52.0	0.0	2.4 ± 2.3	0.0	244.0 ± 72.3	0.0	7.2 ± 5.9	0.0	226.0 ± 58.9	0.0
Calanoida	0.0	0.0	0.0	0.0	0.2 ± 0.5	0.0	0.0	0.0	0.1 ± 0.4	0.0
Cyclopoida	0.2 ± 0.5	0.0	8.0 ± 4.0	0.0	0.1 ± 0.3	0.0	2.3 ± 0.6	0.0	0.8 ± 2.0	0.0	4.3 ± 1.5	0.0
Nauplia	2.1 ± 3.0	0.0	68.5 ± 29.5	0.0	1.4 ± 1.7	0.0	176.7 ± 65.6	0.0	0.7 ± 1.3	0.0	31.7 ± 14.5	0.0
Polychaeta	0.6 ± 0.8	0.0	378.0 ± 13.0	1.5 ± 0.5	0.0 ± 0.2	0.0	61.7 ± 20.1	4.7 ± 1.5	0.2 ± 0.4	0.0	45.3 ± 15.0	3.7 ± 2.9
Ostracoda	0.5 ± 0.8	0.0	22.0 ± 1.0	0.0	0.0 ± 0.2	0.0	0.0	0.0	0.0	0.0	7.0 ± 4.0	0.0
Amphipoda	5.7 ± 4.7	10.0 ± 7.8	67.5 ± 1.5	5.5 ± 0.5	0.1 ± 0.2	0.7 ± 1.1	11.7 ± 2.5	2.0 ± 1.0	0.8 ± 1.2	9.3 ± 9.2	19.3 ± 4.7	14.3 ± 9.3
Unidentified	5.7 ± 4.7	9.6 ± 7.9	67.5 ± 1.5	5.5 ± 0.5	0.1 ± 0.2	0.4 ± 0.8	11.7 ± 2.5	2.0 ± 1.0	0.8 ± 1.2	8.8 ± 9.2	19.3 ± 4.7	14.3 ± 9.3
Caprellidae	0.0	0.4 ± 0.7	0.0	0.0	0.0	0.3 ± 0.8	0.0	0.0	0.0	0.6 ± 0.9	0.0	0.0
Isopoda	2.6 ± 2.3	7.4 ± 5.1	29.0 ± 12.0	1.5 ± 1.5	0.3 ± 0.7	1.3 ± 2.0	0.7 ± 1.2	0.0	1.0 ± 2.6	1.3 ± 1.9	2.3 ± 1.5	1.3 ± 0.6
Unidentified	1.1 ± 1.9	7.4 ± 5.1	4.0 ± 3.0	1.5 ± 1.5	0.3 ± 0.7	1.3 ± 2.0	0.7 ± 1.2	0.0	0.2 ± 0.5	1.3 ± 1.9	0.7 ± 0.6	1.3 ± 0.6
Asellota	1.5 ± 2.0	0.0	25.0 ± 9.0	0.0	0.0 ± 0.2	0.0	0.0	0.0	0.7 ± 2.2	0.0	1.7 ± 1.2	0.0
Tanaidacea	0.1 ± 0.3	0.0	4.5 ± 3.5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Galatheoidea	0.0	1.0 ± 2.5	0.0	0.0	0.0	3.3 ± 4.7	0.0	0.0	0.0	1.8 ± 3.8	0.0	0.0
Paguroidea	0.0	0.0 ± 0.2	0.0	0.0	0.0	0.3 ± 0.5	0.0	0.0	0.0	0.0	0.0	0.0
Mysidacea	0.0	0.6 ± 2.7	0.0	0.0	0.0	0.1 ± 0.3	0.0	0.0	0.0	0.0 ± 0.2	0.0	0.0
Bivalvia	0.0	0.0	0.0	1.0 ± 0.0	0.0 ± 0.2	0.0	0.0	0.3 ± 0.6	0.0	0.0	1.0 ± 1.7	0.0
Gastropoda	0.0	0.0	0.0	3.5 ± 1.5	0.1 ± 0.6	0.0	0.3 ± 0.6	0.0	0.0	0.0	0.0	0.0
Acarina	0.1 ± 0.3	0.0	0.5 ± 0.5	0.0	0.1 ± 0.3	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Pycnogonida	0.0	0.0	0.0	0.0	0.0	0.0 ± 0.2	0.0	0.0	0.0	0.0 ± 0.2	0.0	0.0
Turbellaria	0.0	0.0	0.5 ± 1.5	0.0	0.0	0.0	0.7 ± 1.2	0.0	0.0	0.0	0.7 ± 1.2	0.0
Ophiuroidea	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.3 ± 0.6	0.0

Table 3.

Results of PERMANOVA analysis carried out to ascertains the differences in gut contents of H. guttulatus among three habitats (Corallina elongata, sandy bottom and Cladophora prolifera) in terms of total abundance of prey items, preys < 1mm, preys > 1mm, number of higher taxa and community composition of prey items (df = degree of freedom, MS = mean square, Pseudo-F = F statistic, P(perm) = probability level; *** = P < 0.001; ** = P < 0.01; * = P < 0.05, n.s. = not significant).

PERMANOVA Main test
Variable	Source	df	MS	Pseudo-F	P(perm)
Total abundance	Habitat	2	1703.4	40.8	***
	Residual	80	41.7
	Total	82
Prey < 1mm	Habitat	2	1965.5	25.5	***
	Residual	80	76.9
	Total	82
Prey > 1mm	Habitat	2	2235.6	6.5	***
	Residual	80	345.6
	Total	82
Taxa	Habitat	2	1153.5	7.2	**
	Residual	80	160.5
	Total	82
Community	Habitat	2	9061.1	14.0	***
	Residual	80	645.3
	Total	82

Table 4.

Results of PERMANOVA pairwise analysis carried out to ascertains the differences in gut contents of H. guttulatus among three habitats (Corallina elongata, sandy bottom and Cladophora prolifera) in terms of total abundance of prey items, preys < 1mm, preys > 1mm, number of higher taxa and community composition of prey items (P(perm) = probability level; *** = P < 0.001; ** = P < 0.01; * = P < 0.05, n.s. = not significant).

PERMANOVA Pairwise
Variable	Groups	t	P(perm)
Total abundance	Corallina elongata, Sandy bottom	8.7	***
	Corallina elongata, Cladophora prolifera	5.0	***
	Sandy bottom, Cladophora prolifera	4.0	***
Prey < 1mm	Corallina elongata, Sandy bottom	7.3	***
	Corallina elongata, Cladophora prolifera	4.6	***
	Sandy bottom, Cladophora prolifera	2.2	*
Prey > 1mm	Corallina elongata, Sandy bottom	3.8	***
	Corallina elongata, Cladophora prolifera	1.6	n.s.
	Sandy bottom, Cladophora prolifera	1.9	*
Taxa richness	Corallina elongata, Sandy bottom	3.7	***
	Corallina elongata, Cladophora prolifera	3.1	**
	Sandy bottom, Cladophora prolifera	0.6	n.s.
Community	Corallina elongata, Sandy bottom	4.6	***
	Corallina elongata, Cladophora prolifera	2.9	***
	Sandy bottom, Cladophora prolifera	3.1	***

Table 5.

Results of PERMANOVA analysis carried out to ascertains the differences in sediment contents among three habitats (Corallina elongata, sandy bottom and Cladophora prolifera) in terms of total abundance of benthic fauna, organisms < 1mm, organisms > 1mm, number of higher taxa and community composition (df = degree of freedom, MS = mean square, Pseudo-F = F statistic, P(MC) = probability level; *** = P < 0.001; ** = P < 0.01; * = P < 0.05, n.s. = not significant).

PERMANOVA Main test
Variable	Source	df	MS	Pseudo-F	P(MC)
Total abundance	Habitat	2	225.2	36.5	***
	Residual	6	6.2
	Total	8
Organisms < 1mm	Habitat	2	235.5	33.9	***
	Residual	6	6.9
	Total	8
Organisms > 1mm	Habitat	2	94.3	2.7	n.s.
	Residual	6	34.5
	Total	8
Taxa	Habitat	2	772.1	20.6	**
	Residual	6	37.4
	Total	8
Community	Habitat	2	951.8	13.5	***
	Residual	6	70.5
	Total	8

Table 6.

Results of PERMANOVA pairwise analysis carried out to ascertains the differences in sediment contents among three habitats (Corallina elongata, sandy bottom and Cladophora prolifera) in terms of total abundance of benthic fauna, organisms < 1mm, number of higher taxa and community composition (P(MC) = probability level; *** = P < 0.001; ** = P < 0.01; * = P < 0.05, n.s. = not significant).

PERMANOVA Pairwise
Variable	Groups	t	P(MC)
Total abundance	Corallina elongata, Sandy bottom	6.0	**
	Corallina elongata, Cladophora prolifera	9.0	***
	Sandy bottom, Cladophora prolifera	1.7	n.s.
Organisms < 1mm	Corallina elongata, Sandy bottom	6.0	**
	Corallina elongata, Cladophora prolifera	8.4	**
	Sandy bottom, Cladophora prolifera	1.8	n.s.
Taxa richness	Corallina elongata, Sandy bottom	7.0	**
	Corallina elongata, Cladophora prolifera	3.6	*
	Sandy bottom, Cladophora prolifera	2.6	n.s.
Community	Corallina elongata, Sandy bottom	4.7	**
	Corallina elongata, Cladophora prolifera	4.3	**
	Sandy bottom, Cladophora prolifera	2.1	*

2. Experimental design, materials and methods

Data were gathered from 83 specimens of Hippocampus guttulatus collected at Taranto Mar Piccolo in Southern Italy from habitats of different complexity: two highly (Corallina elongata and Cladophora prolifera) and one low complex (sandy bottom) habitat. To investigate a spectrum of prey items present in the habitat so as to determine seahorse's prey preferences, benthic faunal samples were also collected.

Seahorses, selected according to their appearance, were hand-picked by SCUBA divers, morphometrically measured and then transferred to the containers containing filtered seawater (30 μm mesh) and clove oil (0.05%), a natural anesthetic [2], [3]. To obtain gut contents, the technique of stomach flushing was applied [1], [3]. The water inside the container was sieved through 30 μm mesh. The fraction retained on the sieve was preserved in 50 ml tubes and in 4% buffered formalin and Rose Bengal (0.5 g l⁻¹). Benthic faunal samples were collected from the same habitats as seahorses. In each habitat, three replicate cores (with a diameter of 3.7 cm) were considered. Obtained samples were fixed in 4% buffered formaldehyde in filtered (0.3 μm mesh) seawater solution and in the laboratory, organisms were extracted from sediments by different techniques [4], [5]. For both types of samples, the benthic faunal composition was assessed by visual identification under the stereomicroscope. Two size classes of organisms were identified: larger (>1mm) and smaller (i.e. meiofauna < 1mm). A detailed explanation of procedures is provided in [1]. Univariate and multivariate distance-based permutational nonparametric analyses of variance (PERMANOVA) [6], [7] were performed including habitat (three levels: Corallina elongata, sandy bottom and Cladophora prolifera) as a fixed factor.

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