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The kinorhynch species Echinoderes levanderi Karling, 1954 is redescribed. The species can now be recognized by the presence of spines in middorsal positions on segments 4–8, and in lateroventral positions on segments 6–9, with lateroventral spines on segment 9 showing sexual dimorphism; tubes in subdorsal and ventrolateral positions on segment 2, in sublateral positions on segments 4 and 8, in lateroventral positions on segment 5, and in laterodorsal positions on segment 10. Furthermore, the enlarged sieve plates on segment 9 make the species highly characteristic. New records of the species extend its distributional range into the Bothnian Bay where the bottom water salinity drops below 5 ppt, which is the lowest salinity recorded for a habitat with kinorhynchs.
Necropsies of Baltic grey (Halichoerus grypus) and ringed seals (Pusa hispida) presented a rare opportunity to study their acanthocephalan fauna. Both species hosted adults of three species of the genus Corynosoma Lühe, 1904, namely C. magdaleni Montreuil, 1958, C. semerme (Forsell, 1904) Lühe 1911 and C. strumosum (Rudolphi, 1802) Lühe 1904. A comparative morphological analysis of these three species of Corynosoma, combining both light and scanning electron microscopy, was performed for the first time. Sexual dimorphism in the size and shape of the trunk was observed in both C. magdaleni and C. semerme, but there was insufficient material to investigate this phenomenon in C. strumosum. Genital spines were not observed in any of the female acanthocephalans. Three possible explanations for the presence of genital spines in some females, but not others are (i) cryptic speciation, (ii) phenotypic variation and (iii) loss by extraction or shearing when the copulatory cap is released. Copulatory caps were observed on female C. semerme. The size and morphology showed considerable variability and all caps were strongly autofluoresecent.