Spent females of deepwater squid Galiteuthis glacialis under the ice at the surface of the Weddell Sea (Antarctic)

Abstract

Two large (dorsal mantle length 42.5 and 47.5 cm), mated spent females of circum-Antarctic bathypelagic cranchiid squid Galiteuthis glacialis were caught early in March 1992 at the surface of the ice hole in the western Weddell Sea over depths 1915±1920 m by the team of the U.S.A.-Russian Ice Station Weddell-I. The structure of the reproductive system of adult females is described for the ®rst time in detail.Both were gelatinous, devoid of tentacles, with empty or almost empty stomachs. The empty spermatangia (sperm reservoirs of spermatophores) 30±35 mm in length were distributed in the mantle tissues parallel to the mantle 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, parallel (13) or perpendicular (7) to the body axis. In the latter case, they represented probably two mating events. The spermatangia lay nearer to the inner than the outer mantle side and opened by a round window on the inner side; the skin with chromatophores above them remained intact. The spermatozoa had one¯agellum and rod-like heads, length 5.0±5.3 mm, width 1.2±1.5 mm. 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 trophoplasmatic oocytes, length 0.9±1.4, av. 1.0±1.2 mm, were contained in ovaries; only one mature egg (length 3.3 mm, width 2.4±2.5 mm) was found in each female. The absence of oocytes <0.9 mm and 1.5±3.2 mm indicates that the maturation of oocytes proceeds rather synchronously, one large portion of eggs (some tens of thousands) matures in a short time while others degenerate. The residual fecundity is assessed to be approximately 20,000 eggs.It is hypothesized that mating occurs shortly before spawning and that mature males do not undergo gelatinous degeneration 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 implantation is unclear. Spawning probably occurs at depths of adult habitat (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 meso-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.

Reproductive system of the giant squid Architeuthis in South African waters

“…Nomenclature for the oviducal gland is after Nesis, Nigmatullin et al (1998); oviducal gland sections I and II of Nesis, Nigmatullin et al (1998) correspond with the internal and external oviducts of Williams (1909).…”

“…The few studies on the reproductive morphology of squid (Posselt, 1891;Williams, 1909;Nigmatullin, Arkhipkin & Sabirov, 1991;Nesis, 1995;Voight, 1996;Nesis, Nigmatullin & Nikitina, 1998) show that there are considerable differences between families. Some aspects of the reproductive system of Architeuthis have been published (Knudsen, 1957;Nesis, Amelekhina et al, 1985;Aldrich, 1991;Roeleveld & Lipinski, 1991;Norman & Lu, 1997;Förch, 1998) but no detailed study of the reproductive morphology of male and female Architeuthis has yet been published.…”

Brooding and sperm storage by the deep-sea squid Bathyteuthis berryi (Cephalopoda: Decapodiformes)

“…It is not uncommon to find unspawned eggs in female cephalopods that have died following spawning (e.g. Nesis, 1995;Nesis et al, 1998;Laptikhovsky et al, 2007).…”

Determining the daily spawning cycle of the chokka squid, Loligo reynaudii off the South African Coast

“…In chokka squid we found them to degenerate to a similar extent within 14 h. The duration of postovulatory follicles could have been underestimated because it becomes difficult to distinguish old post-ovulatory follicles from old atretic follicles. While there are several accounts of the occurrence of post-ovulatory follicles in other cephalopods (Nesis et al 1998, Laptikhovsky et al 2002Macewicz et al 2004) there are no reports describing their longetivity and subsequent degeneration. They probably exist for a relatively long time in ''big-bang'' very coldwaters spawners, like G. glacialis (Nesis et al 1998) and in species with very large eggs, e.g.…”

“…Post-ovulatory follicles have been identified in cephalopods by Nesis et al (1998), Melo and Sauer (1999), Laptikhovsky et al (2002) and Macewicz et al (2004). However no system of classification of the different stages exists and there is no knowledge of how long such stages last.…”