Presence of two new species of suctorian (Protozoa: Ciliophora) epibiont on the marine crustacean isopod Excirolana chiltoni

Abstract

Specimens of the marine isopod Excirolana chiltoni collected in Hokkaido (northern Japan) showed epibiont protozoan ciliates belonging to two species of loricate suctorian: Acineta hokkaidensis sp. nov. and Acineta excirolensis sp. nov. Acineta hokkaidensis is larger, with an elongated body covered by a lorica. The short stalk had 15–18 longitudinal striations. The contractile vacuole was located apically. The macronucleus was posterior. Two fascicles of capitate tentacles located at the edges of the apical area project through the anterior aperture of the lorica. The suctorians were found on the pereiopods and antennae of the isopod. Acineta excirolensis which is smaller and triangular in shape, showed a very wide lorica and a noticeably long stalk. At the edges of the apical region there were two lobulate actinophores, each with a fascicle of capitate tentacles. The contractile vacuole was anterior and spherical, and the macronucleus was central. These suctorians were attached as planobionts on the pereiopods of the isopod. The taxonomic position of both species was analysed in relation to other similar species previously described.