Abstract
A description is based on 21 males and 20 females obtained from the gills of halibut Hippoglossus hippoglossus (L.), caught off East Greenland in 1994. Until now the type male has been unique and inadequately described. Both sexes were studied in light microscopy and SEM. The mean length of males and females was l.18 and 7.36 mm, respectively. The antennule, legs and caudal rami of male are comparatively more prominent than those of the female, and the shapes of cephalothorax and trunk are different. The cephalothorax with cuticular ridges, constitutes about 114 of total length of the male. Second pedigerous somite is larger than the first one. The trunk is club-shaped with characteristic cuticular teeth ventrally and rounded posterior extremity, different from that of female. Abdomen is large, I-segmented, and with long and slim caudal rami. Both sexes have frontal organ.
Males were compared with Scott's specimen and the six other known Hatschekia males. Hatschekia reinhardtii Wierzbicka is synonymous with H. hippoglossi. This is the first description of a male hatschekiid based on SEM.
