Mating behaviors of pharaoh cuttlefish Sepia pharaonis

Abstract

This study aimed to elucidate details of mating behaviors in the pharaoh cuttlefish S. pharaonis, with an emphasis on male behavioral adaptations that are related to sperm competition, such as sperm removal, mate guarding, and re-copulation. Observations in the laboratory showed that copulations occurred in the head-to-head position, and lasted about 10 minutes. When copulating with a recently mated female, the male exhibited sperm removal behavior, by using the sucker side of his third arms to scrape off spematangia deposited during previous mating. The male spent the first 1.5 minutes of copulation to remove on average 34% of previous male’s spermatangia before transferring his own to the ventral region of the female’s buccal membrane, using the hectocotylized 4th left arm. Spermatophore transfers occurred in sets of two closely consecutive transfers, each set separated by 1.5 minutes of placement phase. The whole copulation session consisted of 8-10 transfers. Nine spermatophores were passed during each transfer, and a total of about 60 were successfully deposited during a single copulation. After mating with 2 males, the female’s buccal membrane had about 100 spermatangia attached to it. Of these, 43% belonged to the first male, and 57% belonged to the second male. Most males guarded the female closely after copulation, and after about 50 minutes, re-copulated with her again regardless of the presence of another available female.