First Description of Pumpkinseed Lepomis gibbosus (L.) as a Possible Second Intermediate Host for Triaenophorus nodulosus (Pallas, 1781) (Cestoda, Pseudophyllidea) in Germany

Within the scope of a comparative study on Triaenophorosis in perch (Perca fluviatilis L.) 67 pumpkinseed (Lepomis gibbosus L.) from Lake Schreckensee in south-western Germany were examined. Prevalence of the tapeworm Triaenophorus nodulosus (Pallas, 1781) in pumpkinseed was 38.8%. Plerocercoids were detected in liver tissue, either as free larvae or encapsulated. Capsules often contained caseous material with damaged or destroyed plerocercoids. Differences in infestation between pumpkinseed and perch, the main second intermediate host, were observed. This is the first report about pumpkinseed as a possible second intermediate host for T. nodulosus in Germany. scribed in south-western Germany from the River Neckar near Heilbronn (Wild, 1903). Within the scope of a comparative study on Triaenophorosis in three lakes in south-western Germany, pumpkinseed were examined for infection with T. nodulosus in one of these lakes (Lake Schreckensee). In Lake Schreckensee this neozoon was probably introduced by aquarists and forms an abundant, self-sustaining population (Zintz, 1986). In this report, infection of pumpkinseed with larvae of T. nodulosus in Germany is described for the first time. Materials and Methods Lake Schreckensee is located in south-western Germany at an altitude of 568 m (Fig. 1). It has a surface of 32 ha, maximum depth of 11.3 m and mean depth of 6.1 m (Zintz, 1986). The lake is meso-eutrophic (Haertel, 1995). In Introduction Triaenophorus nodulosus (Pallas, 1781) is an intestinal parasite in its definitive host pike (Esox lucius L.). First intermediate hosts are copepods. More than 60 fish species, excluding most cyprinids, have been described as a second intermediate host for this parasite, including perch (Perca fluviatilis L.) and pumpkinseed (Lepomis gibbosus (L.)) (Kupermann, 1973). In contrast to perch as a circumpolarly distributed intermediate host, pumpkinseed is known as an intermediate host for T. nodulosus in North-America (Kupermann, 1973). A survey on parasite fauna of pumpkinseed in Poland showed no T. nodulosus or other cestode infection (Piasecki & Falandysz, 1994). In Lake Bracciano, Italy, L. gibbosus was infected with T. nodulosus (unpublished data of Di Pasqua, 1968, cited in Scholz et al. 1992). Pumkinseed was introduced to Germany in 1880 (Welcomme, 1988) and was first deBull. Eur. Ass. Fish Pathol., 20(2) 2000, 84 June 1999 fish were caught by electro fishing and with fyke-net. Total fish lengths were measured to the nearest mm. Livers of 67 pumpkinseed (3.8 –15.9 cm tot. length) and 102 perch (3.8 –18.2 cm tot. length) as well as stomachs and guts of 39 pike (8.885 cm tot. length) were examined in freshly caught specimens. Abundance (mean no. of parasites per fish) and infection rate of infestation with T. nodulosus were determined. Cysts and free worms were separated from liver and gut tissue, respectively, and identified using binocular and light microscope (magn. 100x, 200x, 400x). T. nodulosus was identified according to Bykhovskaya-Pavlovskaya (1964) and Kupermann (1973) using the shape of hooks in scolices as the main characteristic feature. Results Infestation in pumpkinseed and perch differed in abundanceand infection rate (Table 1), with pumpkinseed having a lower infestation than perch. Abundance was underestimated for both fish species because cysts were counted as one worm but they often contained more than one parasite. In perch more cysts than free plerocercoids were found. In pumpkinseed the number of livers infected with free plerocercoids was equal to the number of livers with cysts. Mean number of cysts in perch was more than twice the mean number of cysts in pumpkinseed (Table 1). In contrast free plerocercoids were more frequent in pumpkinseed ( Fig. 2-4). In one pumpkinseed (5 cm) a heavily infected liver was weighed. More than 80% of the liver weight was due to free plerocercoids. In pumpkinseed many cysts contained a milky or dark liquid with fragments of worms. Free plerocercoids or plerocercoids in cysts often showed incompletely formed hooks. Additionally they were of brown colour and therefore relatively opaque. In contrast to pumpkinseed, 10 km Constance Lake Constance Friedrichshafen Lake Schreckensee Ri ve r S ch us se n