THE HECTOCOTYLUS AND OTHER REPRODUCTIVE STRUCTURES OF BERRYTEUTHIS MAGISTER (TEUTHOIDEA, GONATIDAE)

Taxonomic studies of teuthoids have emphasized characters of the hecto cotylus, a modified arm that male squids use in copulation. Although g onatid squids reportedly lack a hectocotylus, one of the arms in the f ourth, or ventral, pair is reported here to be modified to form a hect ocotylus in male specimens of Berryteuthis magister magister (Berry, 1 913) collected in the eastern Pacific and Bering Sea. The stalks of th e eighth to the seventeenth suckers from the beak are enlarged in both the dorsal and medial dorsal sucker rows. The hectocotylus may have r emained undetected because the changes are comparatively subtle and af fect the middle, rather than the distal, part of the arm. These factor s and the small size of males in fishery trawls from the western Pacif ic seem more likely to explain the difference between these specimens and reports of western Pacific specimens of B. magister than does spec ies-level separation of the populations. This hypothesis is supported by the similarity of spermatophores, sperm reservoirs, and ovarian egg s from eastern Pacific specimens reported here to those previously des cribed from western Pacific specimens.