Metacercariae of Bucephalus polymorphus Baer, 1827 described in Knipowitshia caucasica in Egirdir Lake, Turkey

During the period from October to December 2001, Bucephalus polymorphus metacercariae were described in a new host, Knipowitshia caucasica from Lake Egirdir. A total of 614 fish were collected and the intensity of invasion varied from 10 to 120 parasites per fish. Prevalence of metacercariae of B.polymorphus was 100%, and encysted metacercariae of B.polymorhus were observed in the muscle of the host. In spite of the high level of infection with metacercariae, mortality was not observed in K. caucasica from the Lake. Metacercarial infections caused by Bucephalus spp (Trematoda: Bucephalidae) are common in fish living in freshwater and estuarine environments (eg. Berrilli and Dezfuli, 2002; Hoffman,1975; Paperna,1996)). Larval bucephalosis due to Bucephalus polymorphus caused severe epizootics and high mortality of cyprinid fish in the Seine River, France and Wda River, Poland (De Kinkelin et. al, 1967) and high losses were observed due to an outbreak of the same disease in fish in the Main river, Germany (Hoffmann et. al,1990). An infestation by B. polymorphus was also investigated in the intestine, pyloric caeca and stomach of pike-perch,Stizostedion lucioperca in lake Egirdir,Turkey (Yıldırım et. al.1996). In another study, pike-perch was found to be a definitive host for B. polymorphus (Markevich, 1963), but its first intermediate host was Dressenia polymorpha. After leaving the first intermediate host, cercariae penetrated the gill tissue and skin of cyprinids, where they encysted as metacercariae (Yıldırım et.al.1996). Knipowitschia caucasica (syn. Pomatoschistus marmoratus), a small member of the Gobiidae (from 0.8-3.5cm), has been a shallow water inhabitant of Lake Egirdir for the last ten years. In this report, K.caucasica is described as a new intermediate host of B. polymorphus metacercariae in Egirdir Lake. A total of 614 K.caucasica were collected by hand-nets from the shallow water of Lake Egirdir from October to December 2001. Lake Egirdir is an oligotrophic lake located in south western Turkey. The economically important fish species of the lake consist of pike-perch (Stizostedion lucioperca), carp (Cyprinus carpio) and vimba (Vimba vimba tenella). The pikeperch is the main catch of the local fisherman. K.caucasica were transported live to the laboratory and examined as soon as possible capture. Both internal and external organs were thoroughly inspected for parasites according to standard protocols (Skrjabin,1964; Hoffman, 1999) The skin was examined unBull. Eur. Ass. Fish Pathol., 23(4) 2003, 202 der a stereomicroscope.The anatomical and morphological features of metacercariae were investigated by light microscopy. For histological examinations, fish bodies were fixed in neutral buffered formalin. The samples were vacuum-embedded in paraffin, and sagitally sectioned at 6-7 micrometres. The sections were stained with H&E.; Encysted metacercariae of B. polymorphus were found in the skin of K caucasica. Prevalence of metacercariae was 100%, and this and other demographic data are recorded in Table1. The intensity of invasion varied from 10 to 120 metacercariae per host. Bodies of metacercaria were elongated (Fig. 1) with a suckerlike rhyncus, with seven tentacular appendages and an oral opening in the middle third of body (Fig. 2). The excretory vesicle and intestine were tubular and short respectively. Metacercarial body length varied between 1350 and 1520 micrometres (Fig. 3). During microscopic examination, the metacercariae were found in muscles of K. caucasica ( Fig. 4). The pike-perch, Stizostedion lucioperca was introduced to Lake Egirdir in 1955. During subsequent years the pike-perch population increased substantially while the number of cyprinid fishes decreased. However, pikeperch catch has declined over more recent years through inadequate availability of food and they have became more sensitive to bacterial and parasitic infections (Diler and Yıldırım 1996, 1997, Yıldırım et al.1996). Yıldırım et. al.(1996) investigated the parasitic fauna of pike–perch in Lake Egirdir and B.polymorphus was determined as an endoparasite of S. lucoperca. The prevalence of the parasite ın pike-perch were found to be 54.8% and 100% in 1994 and 1995 respectively, and metacercariae of B.polymorphus were also found in the gills and skin of cyprinids. In the current paper,however, K. caucasica was iden) N ( t s o H e t i s a r a P ) % ( e c n e l a v e r P ) n a e m ( y t i s n e t n I ) * N ( e c n a d n u b A ) 4 1 3 ( e l a m 0 0 1 6 4 . 6 4 0 9 5 4 1 ) 0 0 3 ( e l a m e f 0 0 1 8 8 . 9 4 5 6 9 4 1 Table 1. Demographic parameters of infestation by B.polymorphus, metacercariae. N = Total number of host. N* = total number of individual of parasite. Fig1. Numerous oval-shaped metacercariae of B.polymorphus which oval shaped in the skin of K.caucasica. Fig2. Anterior appendages of metacercaria (X20). Bull. Eur. Ass. Fish Pathol., 23(4) 2003, 203 tified as a new intermediate host for metacercariae of B.polymorphus in Egirdir Lake. Metacercariae form massive infections in ju-venile fish and these have been implicated asan important cause of natural mortalities(Paperna,1996). Larvae of B.polymorhus havecaused high mortality of cyprinid fish (Rutilusrutilus) in the Seine (de Kinkelin, et.al.,1967).A similar situation was found in the MainRiver ( Hoffmann.et.al. 1990) and the latterauthors observed high losses due tometacercariae of B. Polymorphus, especially incyprinids during a period of a sudden in-crease in water temperature. Hoffmanet.al.(1990) stated that eutrophication of thewater system and overcrowding of fish spe-cies may causes outbreaks of parasitosis Theexternal symptoms of the disease were foundto be congestion and haemorrhagie in themouth and bases of the caudal and anal fins(de Kinkelin et.al.1968). Septic necrosis of finsof affected fish was also described. Further-more, in experimental infections, cercariae ofB.polymorphus caused muscle necrosis in troutfry (de Kinkelin et.al. 1985). In this study, weobserved massive metacercarial infections inK. caucasica and large, numerous cysts of B.polymorphus detected in host muscles, but hostmortality was not observed ReferencesBerrilli,F., Dezfuli, B.S., (2002). Description ofB.anguillae (Trematoda:Bucephalidae) a parasiteof the eel Anguilla anguilla from a brackishwater lagoon of the Adriatic Sea. J. Parasitol.88, 382-387 Diler, Ö., Yıldırım,M. Z., (1996-1997). A Studyon the Parasitic Infection (Bucephaluspolymorphus Baer, 1827) and MotileAeromonad Septicaemia in the pike-perch(Stizostedion lucioperca (L.1758 ) of the EgirdirLake. Süleyman Demirel University. Journalof Egirdir Fisheries Faculty 5:221-229. De Kinkelin, P.,Besse, P., Jolivet,G.,Tuffery,G.,(1967). Pathogenic effect of the cer-caria of Bucephalus polymorphus(Baer,1827)(trematoda, Bucephalidae) on thefish population of Seine basin.ComptesRendus Hebdomadaires Des seances de’lAcademia Des Sciences Serie D: SciencesNaturelles 19, 2321-2324 De Kinkelin,P. Besse,P. 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