Occurrence of Mysidacea (Crustacea) in the Pacific Sector of Antarctica and Distribution of Antarctomysis ohlini in Terra Nova Bay (Western Ross Sea)

Abstract

During the summer Italian Antarctic Expeditions of 1987–88 (Polar Queen cruise) and 1989–90 (Cariboo cruise), mysids were collected in Terra Nova Bay and the western Ross Sea (268 and 572 samples, respectively), by a multinet BIONESS. Four species (Boreomysis brucei, Caesaromysis hispida, Dactylabblyops hogdsoni and Euchaetomera zurstasseni) were caught in the Pacific sector of the Southern Ocean and western Ross Sea while Antarctomysis ohlini was the only species found in Terra Nova Bay. It reached maximum densities in the southern part of the bay in deep straits and trenches. The absence of Antarctomysis maxima in both BIONESS samples and in the gut contents of coastal benthic fishes suggests that A. maxima inhabited the outer shelf of Terra Nova Bay, while A. ohlini was confined in the deeper trenches of the bay. The generation time from egg to egg for A. ohlini in Terra Nova Bay was assumed to be 5 years. The growth rate of juveniles was estimated to be about 1 mm per month and the newly moulted young CO caught at Terra Nova Bay in January were about 3 months old. Gut content analysis confirms that A. ohlini was a generalist during its life cycle. Diatoms were the most important group in the juvenile diet composition. The ice-algae Fragilariopsis curta dominate the diatom assemblages in all samples. Coprophagy seems to be the principal feeding in juveniles (age 0 and age 1+), whereas diet diversity increased with increasing size in the species.