Sex-related variability of rostrum morphometry of Aristeus antennatus (Decapoda: Aristeidae) from the Ionian Sea (Eastern Mediterranean, Greece)

Sex-related rostral variability was studied in the aristeid shrimp Aristeus antennatus from the Eastern Ionian Sea (Mediterranean). Shrimps were collected on a monthly basis from December 1996 to November 1997 using a commercial bottom trawl in a depth range of 446-728 m. Female relative growth of rostrum proved to be negative allometric both seasonally and in the pooled annual data set. Males on the other hand, showed no or negative correlation of rostrum length with size. Mature males with short rostra dominated in the male population all year around. The appearance of males with long and intermediate rostra during winter, which disappear thereafter in favour of those with short rostra, indicates that rostrum shortening takes place during the end of winter. The increase of mated females during spring supports the hypothesis already addressed by other authors on the function of the male short rostrum in this species mating behaviour. Nevertheless, the paucity, in comparison to other Mediterranean populations, of males with long or intermediate rostra could indicate that for the bulk of the male population, the process of rostrum shortening in the Eastern Ionian Sea occurs outside the geographical locality or depth range sampled.