Bucephalus polymorphus

Abstract: Two types of bucephalid cercariae are reported from the bivalve Anodonta anatina in two Finnish lakes. One, Type A, resembles in gross morphology the cercaria of Bucephalus polymorphus, and the other, Type B, resembles the cercaria of Rhipidocotyle campanula. Type A daughter-sporocysts develop more slowly, have a greater cercarial productivity and exhibit a differential diurnal rhythm to that of Type B. Cercariae of Type A have a shorter longevity than Type B and tend to encyst in the fins rather than the gill-arches of fish intermediate hosts. The main definitive host of Type A is pike Esox lucius and, in the case of Type B, perch Perca fluviatilis. Adults of Types A and B are morphologically very similar and both species belong to the genus Rhipidocotyle.

Abstract: Four families of trematodes were observed in histological sections during a 1992–1997 investigation of the parasites of zebra mussels Dreissena polymorpha. These included Aspidogastridae, i.e., Aspidogaster, Echinostomatidae, Bucephalidae, i.e., Bucephalus polymorphus, and Gorgoderidae, i.e., Phyllodistomum folium. This article describes the precise location of these trematodes in the tissues of D. polymorpha, provides graphic evidence of their effect on the organs they inhabit, and highlights the distinguishing morphological characteristics. Evidence of defense reaction of host to trematode infection, i.e., encapsulation of Aspidogaster and nacrezation of B. polymorphus, is also presented and is the first such report for zebra mussels. The histological photomicrographs included represent the first comprehensive series published on trematode infection of zebra mussels. These images, in conjunction with the morphological descriptions presented, should assist researchers in identifying the 4 major trematode...

Abstract: Dreissena polymorpha were dissected and examined for endosymbionts from 17 waterbodies in Belarus - the country through whose waterways zebra mussels invaded Western Europe nearly two centuries ago. Fourteen types of parasites and other symbionts were observed within the mantle cavity and/or associated with internal tissues, including ciliates (Conchophthirus acuminatus, Ancistrumina limnica, and Ophryoglena sp.), trematodes (Echinostomatidae, Phyllodistomum, Bucephalus polymorphus, and Aspidogaster), nematodes, oligochaetes, mites, chironomids, and leeches. Species composition of endosymbionts differed among river basins and lake systems. The most common endosymbiont was the ciliate C. acuminatus. Its mean infection intensity varied significantly among waterbodies from 67 ± 6 to 3,324 ± 556 ciliates/mussel.

Abstract: Three species of bucephalid digeneans are known in European freshwater habitats. In this study parthenitae of Rhipidocotyle campanula (Dujardin, 1845) and R. fennica Gibson, Taskinen & Valtonen, 1992, infecting unionid bivalves, and adult Bucephalus polymorphus von Baer, 1827 from perch (Perca fluviatilis L.) were investigated using karyological analysis and DNA sequencing. Our previously published data on genetic characteristics of parthenitae of B. polymorphus from Dreissena polymorpha Pallas were used for comparative analysis. Ribosomal DNA sequences (ITS2 and 28S rDNA) were used to estimate the phylogenetic relationships of the three bucephalid species. Very close phylogenetic affinity between investigated species was revealed; the sequence difference between the two species of Rhipidocotyle Diesing, 1858 (3.78% based on 28S) was comparable with intergeneric differences observed in comparisons of B. polymorphus with R. campanula and R. fennica (3.43% and 4.49% based on 28S, respectively). A high degree of similarity was noted in karyotype structure of the two species of Rhipidocotyle. The diploid chromosome sets consist of 14 bi-armed chromosomes with the first pair of metacentric elements markedly larger than the remaining chromosomes. This chromosome set structure is also specific to B. polymorphus. One specimen of Anodonta anatina L. was infected with tetraploid R. fennica (4n = 28). On the basis of karyotype characters and molecular data, species of the genus Rhipidocotyle cannot be recognised as more closely related to each other than to B. polymorphus. Our findings of Lithuanian and Ukrainian populations of unionid mussels infected with R. fennica provide evidence that this species occurs not only in Finland but also in Central and Eastern Europe. Previous reports of B. polymorphus in unionids in these regions are equivocal because of possible confusion with R. fennica.