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. 2024 Oct 10;49(1):207–214. doi: 10.1007/s12639-024-01749-0

First report of nematode parasite, Camallanus cotti (Camallanidae) (Fujita, 1927) in Barilius bola (Cyprinidae) (Hamilton 1822), from Jaldhaka river of North Bengal, West Bengal

Chayanika Roy 1, Santi Ranjan Dey 1, Priya Roy 2, Riya Mondal 2, Biplab Bhowmik 2,✉
PMCID: PMC11832821  PMID: 39975612

Abstract

In the present study the parasitic nematode, Camallanus cotti (Camallanidae) was identified for the first time in a new host fish, Barilius bola (Cyprinidae), from the Jaldhaka river in North Bengal, the northern part of West Bengal, India, during the period from January 2023 to December 2023. The parasite infected the gastrointestinal region and was protruding from the anal opening, showing excessive mucus secretion in the anal region of its host. Sixty-six (58.41%) out of 113 medium-sized fish were infected. Marked variations in the prevalence, mean intensity, and relative abundance were observed in the summer. These variations might be due to the environmental conditions during different seasons and the presence of an intermediate host for this parasite. Worms were described morphologically and morphometrically by light microscopy and scanning electron microscopy (SEM). Previously identified novel characters were confirmed and reassessed. More studies are required to determine the internal problems of the fish and the impact, establishment and spread of this parasite.

Keywords: Camallanus cotti, Barilius bola, Nematode parasite, North Bengal, Light microscopy, SEM

Introduction

Freshwater bodies are endowed with an extensive variety of fish fauna. One of the major and leading fish family is family cyprinidae. The Northern side of West Bengal is well known as North Bengal and in Bengali term the “Uttarbanga.” The Dooars region of North Bengal is situated in the foothills of Himalaya and consequently rich with many rivers originating from the Himalaya, the major rivers are Teesta, Torsa, Jaldhaka, Kaljani etc. which are the major source of riverine fishes in Dooars. The rivers of North Bengal are rich with tropical and coldwater fishes (Jayaram and Singh 1977; Sarkar and Pal 2008, 2015) which fall under different families, Cyprinidae being the predominant one. Among the fishes that are found in North Bengal, 32 genus are under family cyprinidae and 7 species are under genus Barilius(Sarkar 2021). Barilius is the most popular genus which gains its popularity due to its appearance and taste. Barilius bola which is commonly known as ‘Ghol’ found in the rivers of North Bengal is also popular among the local inhabitants of Dooars region due to its delicacy. It is under the family cyprinidae. The average length of the fish is 40 cm (Chanda 2013). It is a carnivorous species that feeds on small fishes. Its silvery white colour gives it attractive look (Gupta 1983). During this study it was observed that this fish was found to be infected by certain internal parasites and the infection varies with seasons. The infection of parasites in fishes may impede the consume value of the fishes and diminish the fish production both in culture and capture fisheries by eventually causing death of fishes (Knudsen et al. 2002). Researches conducted on fish parasites from North Bengal describes different myxozoan fish parasites (Banerjee et al. 2021). Helminths are the metazoan parasites that can infect fishes are yet to be explored in the fishes of different regions of North Bengal. Family Camallanidae is one of the nematode family that have three subfamilies: Camallaninae, Procamallaninae and Paracamallaninae which infects fishes, amphibians and reptiles (Mascarenhas & Muller 2017). Camallanus cotti is a nematode parasite frequently found in ornamental fishes. Two species of genus Cammallanus was reported from West Bengal Camallanus anabantis from fish Anabas testudineus and Camallanus kulasirii from Ophiscephalus punctatus (De and Ghosh 1989; De 1999). The present study describes about a species of Camallanus, parasitizing carp fish Barilius bola, one of the locally available Cyprinide fish found in North Bengal. This is a gut-inhabiting nematode. Its biology in wild is yet to be identified. The nematode attaches itself to the wall of the gastrointestinal lining of fish hosts by its buccal capsule to feeds on blood of the fish host by partially invading the intestinal wall. Light infection of nematodes apparently has no noticeable effect on its host but large number of infestations may be often fatal for the host fish (Stumpp 1975). Massive infection can cause parasites to come out from the anal opening. The results of the infection are rectal inflammation, anaemia, weakness, and subsequently even death of the fish. Sometimes it may also find to influence the sexual behaviours of the hosts fish (Wu et al. 2007). Considering the importance of this parasite the aim of this present paper is to represent the occurrence of C. cotti with different seasons and morphology using light microscopy and scanning electron microscopy.

Materials and methods

Collection of samples

A total of 113 medium-sized (13 cm to 20 cm) Barilius bola (Hamilton 1822) specimens were collected from the Jaldhaka river in North Bengal, West Bengal, India, during the period from January – December 2023. The specimens were dissected and the intestines were precisely examined for the presence of helminth parasites. The reddish-coloured nematodes that protruded from the anal opening and posterior region of the gut were collected following the standard technique and stored after fixation in 70% ethanol.

Calculation of parasitic occurrence

Calculations for determination of seasonal occurrence of C. cotti in Barilius bola was followed Margolis et al. (1982).

Parasitic frequency index (PFI)

The Parasitic Frequency Index (PFI) was calculated by taking the percentage of the number of individuals of a hosts infected by a particular parasite species against the total number of hosts examined in a particular area under investigation.

graphic file with name 12639_2024_1749_Article_Equ1.gif

Mean intensity

The mean intensity was calculated by taking total number of individuals of a particular parasite species in a sample of host fishes against number of infected hosts fishes in the sample.

graphic file with name 12639_2024_1749_Article_Equ2.gif

Relative density /Abundance: The relative density or abundance was calculated by taking total number of individuals of a particular parasite species in a sample fish host against the total number of host fishes examined in that sample.

graphic file with name 12639_2024_1749_Article_Equ3.gif

Light microscopic study of nematodes

The nematodes isolated from the fish, were prepared for light microscopy by doing further dehydration in upgraded ethanol series and cleared in glycerine (Lebanan and Mohilal 2021). Some were stained with eosin and mounted in DPX. Photographs were taken in Olympus BX43 microscope and measurements were taken in CARL ZEISS trinocular stereozoom microscope, model: stemi 508, SN: 3,951,006,519 and identified generically according to Yamaguti 1941; Soota 1983. Measurements were done in micrometers for all morphological characters.

Scanning electron microscopic study

Some nematodes were prepared for SEM (Scanning Electron Microscopy). They were washed in PBS and prefixed with 2.5% glutaraldehyde in 0.1 M PBS (pH 7.2) for 3 h at 4 ͦ C. The sample nematodes were then again washed in PBS. Secondary fixation was done using 1% osmium tetroxide at 4 ͦ C for 1 h. The samples were then washed in MQ water. Complete dehydration was performed with the help of upgraded ethanol series (30- 100%). The samples were then dried by critical point drying in CO2 and then mounted on aluminium stubs coated with 20 nm gold plate (Moravec and Justine 2006). After gold platting the sample was ready for scanning electron microscopy. Pictures were taken by Carl Zeiss, Gemini, Sigma 300 Scanning microscope.

Results

One hundred thirteen B bola were investigated for the presence of C. cotti. From these investigated fish, 66 were positive for C. cotti with an overall prevalence of 58.41%. All the infected fish were showing swelling and redness in their anal opening i.e., in the distal portion of the intestine (Fig: 1 A). Several reddish worms extended outward from the anal opening of the infected fish (Fig. 1B); some of the worms were attached to the wall and some were free in the rectal lumen of the fish. The infected area was associated with high mucus secretions. It was also observed that fish were more infected during the summer, and the prevalence, mean intensity, and relative density were higher in the premonsoon period compared to the other seasons. The prevalence, mean intensity, and relative density in the premonsoon, monsoon, and postmonsoon periods were 78, 3.4, 2.68; 47, 2.5, 1.17; and 47.3, 3, 1.42, respectively. (Table 1).

Fig. 1.

Fig. 1

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C. cotti infected B. bola (A) showing swelling in the anal opening(arrow). (B) Live nematode protruding from the anal opening

Table 1.

Prevalence, mean intensity and abundance of C. Cotti infecting B. bola in different seasons from January 2023 to December 2023

Season Total no of fish examined Infected Noninfected Prevalence (%) Total no. of parasite recovered Mean intensity Relative density /Abundance

Premonsoon

(March-June)

 41 32 09 78 110 3.4 2.68

Monsoon

(July- Oct)

 34 16 18 47 40 2.5 1.17

Postmonsoon

(Nov-Feb)

 38 18 20 47.3 54 3 1.42
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General description ofCamallanus cotti Fujita 1927; Figures: Fig. 2 (A-F); Fig. 3(A-F); Fig. 4(A-E).

Fig. 2.

Fig. 2

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Photomicrographs showing C. cotti worms. (A) Unstained worm after fixation. (B) stained worm by eosin-stained (C) Unstained anterior portion of female. (D) Unstained tail portion of female (E) Anterior portion of male after eosin stain. (F) Tail portion of male after eosin stain

Fig. 3.

Fig. 3

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Scanning electron microphotograph of C. cotti. (A),(B) Dorsoventral view of cephalic region, (C) tail region of male (D) Anterior portion. (E) Tail region of female (F) Cephalic end more focused. Abbreviations: c- cephalic papilla, p: sclerotized plate of buccal capsule, t: trident

Fig. 4.

Fig. 4

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Camallanus cotti Fujita 1927(camera lucida drawing in lateral view), A- Anterior end of gravid female, B- Anterior end of adult male, C- Abdominal region of gravid female showing the vulva, D- Tail of adult male, E- Tail of adult female. Scale bars A, B, E = 50 μm, C, D = 100 μm

Synonyms

Camallanus zacconis Li 1941; C. fotedari Raina and Dhar 1972; C. moraveci Petter, Cassone and France,1974. (Moravec and Justine 2006)

Description(N = 10)

The C. cotti parasite is under Phylum-Nematoda, Order-Spirurida, Superfamily- Camallanoidea, Family-Camallanidae, Genus- Camallanus, Species- cotti (Gaber and Maher 2021).

Reddish slender medium-sized nematodes with round anterior and narrow posterior end were observed. Ten individuals (five males and five females) of this specimen had been used to describe morphological features and measurements. Body of the worm was covered with fine transversely striated cuticle and large orange-brown buccal capsule present in those worms which is typical for the genus Camallanus. The buccal capsule built with two sclerotized lateral valves. Valves of the buccal capsule was roughly hexagonal in the lateral view with a depression in middle of the tip. Each valve supported with 14–18 smooth longitudinal ridges nearly extending to basal ring, some ridges were much larger than others, some were shorter. Anterior ends of ridges penetrating mouth resembled small teeth of jaw. A well-developed three-pronged spear (Tridents) placed dorsally and ventrally of the buccal capsule and exceeding to some extent to the posterior border of the buccal capsule. Prongs of tridents were symmetrical in shape and length. The mouth aperture slit shaped, dorsoventrally extended, and surrounded by sclerotized plate. Four cephalic papillae and two lateral amphids were situated in the cephalic region surrounding the mouth. Two pairs of sublateral perfunctory sclerotized plates with clearly widened posterior end, extending from the mouth about one fourth of length of valves were observed. Another small, perfunctory diagonal rod-like sclerotized formation present at top of each valve (between bases of two sublateral plates), forming a kind of support of amphid. A sclerotized basal ring present at the bottom of the buccal capsule made a border line between buccal capsule and the oesophagus. Muscular oesophagus slightly narrower than the buccal ring at the proximal end of muscular oesophagus. Oesophagus parted into muscular and glandular section from the posterior portion of basal ring respectively. Glandular oesophagus was slightly larger than muscular oesophagus. The muscular part of the oesophagus encircled by nerve ring. Excretory pore situated next to the level of nerve ring. Deirids slightly asymmetrical, small and situated at about two thirds of muscular oesophagus. It was observed that sexual dimorphism was prominent and can be identifiable by some distinguishing characters. All the measurements were taken in micrometers and the means are in parentheses.

Male(N = 5): Total length of the body 1698–3450 μm (2848 μm), maximum width 87.439 –186.332 μm (128.16 μm), Buccal capsule length 83.64 –90 μm (86.89 μm), width 72.44 –79.58 μm (76.32 μm), Basal ring length 9 μm -9.01 (9 μm), width 60 –79 μm (71.76 μm), average size of the ring 9 μm x 71.76 μm. Buccal capsule with longitudinal ridges of about 18 (18). Prongs of the tridents length 62.71 –70.1 μm (65.7 μm). Nerve ring from anterior proximity 127–187 μm (167.8 μm). Muscular oesophagus length 372.90 –376 μm (374.26 μm), width 69 –70.5 μm (70 μm) and glandular oesophagus length 470 –472 μm (471.6 μm), width 66 –66.2 μm (66.12 μm). Male worm bears curved tail with edgy end. Tail served with unequal but similar spicules. The larger one 132 –149 μm (142 μm), the smaller one 81 –100 μm (90 μm) in length. Fourteen pairs of pedicles like caudal papillae are present, precloacal 7 pairs, ad-cloacal 2 pairs and post-cloacal 5 pairs. Cloacal aperture from the posterior extremity 102 –126 μm (112 μm). The width of the tail at the cloacal region is 38.07 –49.5 μm (46 μm).

Female(N = 5): Female worms were larger and sturdy than the males. Total length of the body 3428 –7726 μm (5679 μm), maximum width 213 –310 μm (281 μm), buccal capsule length 100 –134 μm (90.8 μm), width 93.2 –122.40 μm (92.49 μm), Basal ring length 9.3 –15 μm (11.86 μm), width 80 –92 μm (84.81 μm). Buccal capsule with 18–20(18) longitudinal ridges. Prongs of tridents 101 –123 μm (111.4) long. Nerve ring from anterior proximity 230 –265 μm (247.6 μm). Muscular oesophagus length 392–564 μm (492 μm), width 86.56–105.6 μm (95.55 μm), glandular oesophagus 523–672 μm (596.6 μm) long and width 77–98 μm (85.8 μm). Vulva from the anterior end 1720 –4125 μm (3113 μm). Females with slender filiform tail. Vagina and uterus well developed. They found ovoviviparous, the eggs and larvae were in the uterus and the ovejector is downwardly directed. Comparative measurements of C. cotti of the present study with those previously recorded are shown in Table 2 .

Table 2.

Comparative measurements of Camallanus cotti of present study with those already recorded

Host fish Body(µm) Buccal capsule(µm) Oesophagus length(µm) Prongs of tridents length(µm) Collection site
length Width length width muscular glandular
Barilius bola Male Male Male Male Male Male Male North Bengal, India(present study)
1698–3450 87.439-186.332 83.64-90 72.44–79.58 372.90–376 470–472 62.71–70.1
Female Female Female Female Female Female Female
3428–7726 213–310 100–134 93.2-122.40 392–564 523–672 101–123
Awaous guamensis) Male Male Male Male Male Male Male New Caledonia, South Pacific (Moravec and Justine 2006)
2600–3630 163–231 96–105 87–93 340–381 367–517 66–81
Female Female Female Female Female Female Female
7000–9440 367–490 147–174 129–150 517–653 571–666 135–156
Beta splendens and Poecilia reticulata Male Male Male Male Male Male Male Brazil(Menezes et al. 2006)
3440–4240 171–220 83–100 76–102 332–377 441–490 65–93
Female Female Female Female Female Female Female
7429–9238 293–336 132–147 122–157 519–588 588–752 72–122
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Taxonomic summary

Type host: Barilius bola (Hamilton 1822), Freshwater carp, order: cypriniformes.

Site of infection: Distal portion of the intestine near anal opening.

Type locality: Jaldhaka River, Jalpaiguri District, West Bengal, India.

Prevalence: 58.4%.

Discussion

During the course of study in the Jaldhaka river in North Bengal, it was observed that the fish B. bola was found to be infected with the parasitic nematode C. cotti(Fujita 1927; Camallanidae). This parasite mainly infects and resides in the gastro intestinal tract of its host. The geographical distribution of this parasite is now thought to be widespread (Evans and Lester 2001; Kim et al., 2002). It has been recorded in fishes under Cypriniformes, Rajiformes, Acipenseriformes, Salmoniformes, Cyprinodontiformes, Scorpaeniformes, Perciformes (Li 1941; Moravec and Justine 2006). Some studies believe that the life cycle of C. cotti involves copepod, Cyclops sp as an intermediate host. (Moravec and Justine 2006; Wu et al. 2007; Levsen 2001; Levsen and Jakobsen 2002). C. cotti was reported in a cyprinidae, wild Giant Danio Devario aequipinnatus from the Cauvery River systems for the first time in the Southern part of the Western Ghats, India. Our present study revealed that the seasonal changes with respect to prevalence, mean abundance, and relative density a high trend in the summer and a low trend in the winter (Table 1). The present findings were similar to the previous data that described the higher trend in summer and suggested that the cause of these variations might be the environmental conditions and the presence of an intermediate host for this parasite (Zhang 1993; Vincent and Font 2003).

The parasites were slender, reddish coloured and protruding from the anal opening of the host fish. The present study illustrates the taxonomically relevant morphological features and measurements of parasitic nematode C. cotti by using both light microscopic and scanning electron microscopic studies. The morphology of C. cotti was first described by Fujita in 1927 in Japan. After that, Yamaguti (1935, 1941), Moravec and Nagasawa (1989), Moravec and Justine (2006), Menezes et al. (2006), and Raja et al. (2018) redescribed it. This study demonstrates the detail of the more clearly visible structure of the buccal capsule, which is typical for the genus Camallanus (Moravec and Santos 2009). The arrangement of cephalic ridges and the spikes of the tridents were observed during light microscopic study as well as SEM. The sclerotized plate surrounding the mouth is seen to grow out of the frontal margin of the cephalic valves. SEM examination based on this specimen, clearly revealed that the anterior end of the cephalic ridges protruding into the mouth typically gives jaw like appearance. This study describes the distribution of cephalic papillae and caudal papillae. Four cephalic papillae, two sub laterally positioned sclerotized plates, and lateral rod like sclerotized structures were observed. It was clearly observed that three equal sized prongs of tridents attached together with a sclerotized elevated portion situated on the dorsoventral sides of the cephalic region. A SEM examination performed on C. cotti confirms some novel structures. Both light microscopy and SEM help us perform a detail analysis of the morphology of this nematode.

In this present work, the parasitic nematode C. cotti(Futija 1927, Camallanidae) was reported first time in a new host Barilius bola( Hamilton 1822; Cyprinidae) from Jaldhaka river, Jalpaiguri district, West Bengal, India.

Acknowledgements

The authors thank the authorities of Diamond Harbour Women’s University, and Rammohan College for providing the necessary facilities to carry out this work. We are thankful to Burdwan University, for letting us perform the Scanning Electron Microscopic studies in their laboratory.

The authors thank the authorities of Diamond Harbour Women’s University, and Rammohan College for providing the necessary facilities to carry out this work. We are thankful to Burdwan University, for letting us perform the Scanning Electron Microscopic studies in their laboratory.

Author contributions

All authors had participated in the study conception and design. Material preparation, data collection and analysis and preparation of manuscripts.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Declarations

Completing interests

The authors have no relevant financial or non-financial interests to disclose.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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