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Aporocotyle simplex fluke from the flounder Hippoglossoides platessoides in Svalbard.
HÁJKOVÁ, Šárka
In my bachelor thesis I studied trematodes from plaice Hippoglossoides platessoides obtained during expeditions to Svalbard in 2014 and 2018. My goal was morphological and molecular processing of the obtained material, which allowed me to confirm the identification of the flukes as Aporocotyle simplex Odhner, 1900. Aporocotyle simplex is a common parasite of plaice, ocurring mainly in Hippoglossoides platessoides, but also in Limanda limanda and Pleuronectes platessa. The species A. simplex is geographically distributed in the Gulf of St. Lawrence in Canada, off the west coast of Sweden, in the Barents Sea and Bering Sea, off the coast of Kamchatka and Greenland. My results showed that the species A. simplex is widespread in Svalbard. In the practical part, I dealt with methods that helped me to identify the studied specimens. I observed the trematode tegumental surface with aid of a scanning electrom microscope (JEOL JSM-7401F). The trematode internal organs were stained with Mayer-Schuberg carmine, which allowed me to observe and draw the mounted specimens using a light microscope (Olympus BX51) equipped with a drawing attachment. Furthermore, for molecular analysis, the DNA was isolated using the commercial Exgene Tissue SV mini kit (GeneAll). The isolated DNA (the gene for the large ribosomal subunit, 28S rRNA) was amplified by PCR, the obtained PCR products were sequenced on an automated sequencer (ABI Prism 3130xl or 3730xl, by SEQme). The newly acquired sequences (three in total) were aligned in the program Geneious 8.0.5with sequences available from GenBank (64 sequences). Phylogenetic analysis of the species relationships within the family Aporocotylidae was performed using the Maximum Likelihood method with TPM2u + F + G4 used as the best model. Aporocotyle simplex falls into a separate branch together with A. michaudi, from which however, it differs substantially by its morphology (distribution of tegumental spines on body and their number in the clusters, number of testes, ratio of esophagus length to body length) and geographical distribution (A. michaudi occurs in the South Atlantic Ocean).
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