SPENT FEMALES OF DEEP-WATER SQUID GALITEUTHIS-GLACIALIS UNDER THE ICEAT THE SURFACE OF THE WEDDELL SEA (ANTARCTIC)

Two large (dorsal mantle length 42.5 and 47.5 cm), mated spent females of circum-Antarctic bathypelagic cranchiid squid Galiteuthis glaciali s were caught early in March 1992 at the surface of the ice hole in th e western Weddell Sea over depths 1915-1920 m by the team of the U.S.A .-Russian Ice Station Weddell-L The structure of the reproductive syst em of adult females is described for the first time in detail. Both we re gelatinous, devoid of tentacles, with empty or almost empty stomach s. The empty spermatangia (sperm reservoirs of spermatophores) 30-35 m m in length were distributed in the mantle tissues parallel to the man tle surface and to each other in the dorso-anterior part of the mantle : 13 in one female, parallel to the body axis, and 20 in the other, pa rallel (13) or perpendicular (7) to the body axis. In the latter case, they represented probably two mating events. The spermatangia lay nea rer to the inner than the outer mantle side and opened by a round wind ow on the inner side; the skin with chromatophores above them remained intact. The spermatozoa had one flagellum and rod-like heads, length 5.0-5.3 mu m, width 1.2-1.5 mu m. The most characteristic features are : a very simple type of blood vessel branching making each micro-gonad currant-like, not grape-like; a very compact disposition of oviducal, nidamental glands and gill, forming a united complex located on both sides of the mantle cavity; and an ovary connected by mesentery along all its length with the continuation of the stomach from the caecum to the end of the gastrogenital ligament. Only immature degenerating tro phoplasmatic oocytes, length 0.9-1.4, av. 1.0-1.3 mm, were contained i n ovaries; only one mature egg (length 3.3 mm, width 2.4-2.5 mm) was f ound in each female. The absence of oocytes <0.9 mm and 1.5-3.2 mm ind icates that the maturation of oocytes proceeds rather synchronously, o ne large portion of eggs (some tens of thousands) matures in a short t ime while others degenerate. The residual fecundity is assessed to be approximately 20,000 eggs. It is hypothesized that mating occurs short ly before spawning and that mature males do not undergo gelatinous deg eneration and do not lose tentacles. Spermatophores are placed on the inner side of the female's mantle with the aid of the male's tentacles and/or arms (less probably by the penis), but the exact mode of impla ntation is unclear. Spawning probably occurs at depths of adult habita t (approx. 500-2500 m), may be multiportional but short; the exhausted female loses neutral buoyancy, rises to the surface and dies. Rising to the surface after spawning is a common feature of females of many m eso-and bathypelagic squids undergoing gelatinous degeneration during maturation (Onychoteuthidae, Gonatidae, Histioteuthidae, Cranchiidae, etc.) and may explain the common occurrence of large deep-water squids in the stomachs of seabirds, including those incapable of diving, and marine mammals.