Digenetic Trematode parasites in two fresh water fishes Ophiocephalus punctatus and Xenentodon cancila from North west Himalayas

The study was conducted during September 2018-August 2019 to study the digenetic trematode infection in fresh water fishes of some of the water bodies viz. Gho-manhasan, Chakrali and Chadwal of Jammu region of J&K union territory. A total of 220 fishes comprising Ophiocephalus punctatus and Xenentodon cancila belonging to families Channidae and Belonidae respectively were examined. A total of 4 digenetic trematode parasites belonging to 4 different families i.e., Euclinostomum heterostomum (Clinostomidae Luhe, 1901); Phyllodistomum tripathi (Gorgoderidae Looss, 1901); Genarchopsis piscicola (Hemiuridae, Luhe, 1901), and Bucephalopsis karvei (Bucephalidae Poche, 1907) were detected. The overall prevalence of digenetic trematode infection was 65.90% and the mean intensity was 3.58. Among these Genarchopsis piscicola showed the highest prevalence (40.38%) with mean intensity 2.95 in the host fish Xenentodon cancila, while in other species the prevalence ranged between 26.23 and 34.62%. Present study authenticates the presence of several species of digenetic trematode parasites in the fish inhabiting freshwaters of J&K union territory.


Introduction
Fish constitutes an important source of food, nutrition, income and livelihood for millions of people around the world. Moreover, fish continues to be one of the most traded food commodities worldwide with more than half of fish exports by value originating in developing countries. Fishes provide a potential habitat to metacercariae of digenetic trematodes. Digenetic trematodes are a diverse group of parasites that use more than one host to complete their life cycle. Avian digenetic trematodes use fishes as secondary intermediate hosts to complete their life-cycles (Bullard and Overstreet 2008). Trematodes are the most diverse group of fish parasite and are present in larval or adult forms in majority of fish species and most of them exist as endoparasites. Digenetic trematode infections cause low weight gain, high mortality and immarketabilty of the infected fish. Currently, fish-borne zoonotic trematodes are the cause of health problems and also affect the public health in many Asian countries (Murrell et al. 2007;Tran et al. 2008;Phan et al. 2010). The present study was therefore undertaken to ascertain the spectrum of digenetic trematodes from fresh water fishes Ophiocephalus punctatus and Xenentodon cancila in Jammu region.

Materials and methods
A total of 220 fish samples were collected from different freshwater bodies of Jammu region; Gho-manhasan stream (32.69ºN latitude, 74.68ºE longitude), Chakrali stream (32.70ºN latitude, 74.65ºE longitude) and Chadwal stream (32.36ºN, 75.35ºE longitude) (Fig. 1). Collected fish samples were brought alive to laboratory. Fishes were anesthetized and thoroughly examined for presences of parasites by carefully dissecting under Stereoscope. The gastrointestinal tract, muscle tissue and other internal organs of the host fish, thus obtained were teased in 0.8% saline and examined for the recovery of the metacercarial or adult stage of trematode parasites. Trematode parasites were flattened between two slides or under slight pressure of slide and coverslip, postfixed in AFA (Alcohol, Formalin and Acetic acid in 85:10:5) and stained with Borax carmine. Afterwards, specimens were dehydrated in ascending series of ethanol, cleared in xylene and finally mounted on glass slides using DPX. Photomicrographs of stained specimens were studied and photographed using microscope Leica M205 C and identified by following the standard literature (Yamaguti 1971;Bray et al. 2008;Pandey and Agrawal 2013). The prevalence of infection and mean intensity (Table 1) were calculated following Bush et al. (1997).

Description
Cysts of E. heterostomum were yellowish and spherical, excretory vesicle, intestinal caeca brownish and are observed on the external surface; excysted metacercariae body elongated, linguiform after fixing measures 4.36-6.54 mm × 2.18-2.49 mm; anterior end of the body truncated and posterior end is rounded; oral sucker sub-terminal, small surrounded by collar-like fold 0.19-0.38 mm × 0.16-0.27 mm; ventral sucker lager well

Remarks
The genus Euclinostomum was established by Travassos, 1928 which have well developed diverticulated ceaca. Moreover, Euclinostomum is the type genus of subfamily Euclinostominae, found in the buccal cavity and in the oesophagus of piscivorous birds, primarily herons and egrets. Many reports of metacercarial and adult forms of E.heterostomum from freshwater fishes have been studied by several workers across the world (Jhansilakshmibai & Madhavi 1997: Britz et al. 1984 Jaiswal, 1957;E.minutus Bhutta and Khan 1975 and E.reticulatum Sudan;1979 (Table 2). In the present fluke oral sucker is subterminal closely resembles to E.reticulatum but smaller than E.bhagavantami and E.minutus. The number of intestinal diverticulae differs in E.bhagavantami (9-12), in E.minutus (12-15) whereas resembles E.reticulatum with 7-12 diverticula. The size of ovary, however show resemblance to E.minutus which is quite smaller than that of E.bhagavantami and E.reticulatum.

Remarks
The genus Phyllodistomum was erected by Braun (1899) for Distomum folium Olfers, 1816 as its type species. Based on the narrow and tubular anterior region and spatulated hind body our specimen belonged to the genus Phyllodistomum. Different species of the genus Phyllodistomum have been reported by several workers (Cribb, 1987;Helt, 2003;Mendoza-Garfias et al. 2005;Ho et al. 2014) from fishes all over the world including that from India (P.loossi Kaw, 1950;P. indianum Jaiswal, 1957; P. tripathi Motwani and Srivastava, 1961;P. srivastavi Rai, 1964;P. cameroni Agarwal, 1966;P.megacotyle Fotedar, 1969; P.mansari Sudan, 1979; P. triangulata Sarwat, 2011;P.betwaensis Sen, 2014;P.punctatai Jithila and Prasadan, 2018). The present species resembles with P.loossi in the relative size of suckers, shape and position of vitellaria, uterus and genital pore. It however differs in the absence of any papillae in suckers and the size of eggs which are smaller and more slender in present form. The present species shows similarities with P.betwaensis but different from P.betwaensis in size of body, size of oral and ventral sucker and position of Vitelline glands with respect to ovary (Table 3). The present species differ further from P.punctati, a species reported from urinary bladder of Channa punctata in ratio of body length to width, size of oral and ventral sucker and various morphological and morphometry features. Present species resembles P.tripathi in having the lateral margins of hindbody provided with indentations, however differs in some morphological features and morphometry like length to width ratio of body, size and shape of ventral sucker and size of testes and ovary. Since, most of the characteristics of the present species bear a close resemblance with P.tripathi hence the identified as P.tripathi reported from freshwater fish Xenentodon cancila of Jammu. 3. Genarchopsis piscicola Srivastava, 1933

Remarks
The genus Genarchopsis was erected by Ozaki (1925) with G. goppo as the type species from the intestine of Mogurnda obscura, Japan. Several species of Genarchopsis have been reported viz. G. ovocaudata Srivastava, 1933 from Ophiocephalus punctatus; G. piscicola Srivastava, 1933