COMPARISONS OF GYMNOPHALLID DIGENEANS FROM NORTH PACIFIC AND BALTIC CLAMS, MACOMA-BALTHICA (BIVALVIA)

Three gymnophallid species in Macoma balthica from the northeastern Pacific Ocean are similar to 3 species in M. balthica from the Baltic Sea. Using light and scanning electron microscopy, we compared the anatomy of the larvae of 2 species of Lacunovermis and of Gymnophallus, and the adults of 2 species of Lacunovermis; recovered from incubation on chick allantoic membrane. The third similar pair of Meiogymnophallus multigemmulus and Parvatrema affinis was restudied with light microscopy. Previously described anatomical differences between the 3 pairs of Pacific and Baltic gymnophallids were nullified in this study. Lacunovermis conspicuus Ching, 1965 is synonymized with Lacunovermis macomae (Lebour, 1908), and Gymnophallus gibberosus Loos-Frank, 1971 is synonymized with Gymnophallus somateriae (Levinsen, 1881). Meiogymnophallus multigemmulus Ching, 1965 is synonymized with Parvatrema affinis (Jameson and Nicoll, 1913), becoming M. affinis n. comb.