The Southern Ocean is probably the last frontier in the field of marine biology. This huge oceanic region is the scene of a very efficient production system yielding high levels of biomass. Within the Southern Ocean food chain the important and conspicuous role played by Antarctic krill is well documented but there is another group of key animals, rarely conspicuous and much less well understood that play a most important intermediate role in the food chain. Although field scientists working in the Southern Ocean have observed an abundant and diverse squid fauna in the diet of vertebrate predators, Antarctic squid have seldom been seen alive. This is in contrast to the situation in seas at lower latitudes where schools of neritic and oceanic squid are regularly encountered at the surface. Marine scientists have rarely been successful in catching Antarctic squid, using either towed nets or jigs, but it has been estimated that standing stock biomass of these organisms in the Southern Ocean may be as high as 100 million tonnes based on an estimate of 30 million tonnes consumed by vertebrate predators. This is clearly a significant resource when compared to the annual catch of the world's fisheries (mostly finfish) which, according to current FAO statistics, amounts to some 100 million tonnes.

The first systematic sampling in the Southern Ocean to capture cephalopods took place 120 years ago aboard HMS Challenger. Over the next century taxonomic knowledge was advanced by expeditions including the Mission du Cap Horn (France), the Valdivia Deep Sea Expedition (Germany), the Discovery expeditions (UK) the Eltanin (USA) and Academic Knipovitch (USSR). Over the last decade Southern Ocean cephalopod research has at last progressed beyond the descriptive phase and is rapidly joining other fields of Antarctic marine biology in its concerns with population biology and trophic systems, Although much taxonomic work remains to be done, ecological studies on the role of cephalopods in the diet of predators has been facilitated by advances in the identification of cephalopod beaks, development of opening-closing nets has allowed fine-scale distribution studies, and as methods for the study of growth, diet and biochemical genetics have advanced, so these have been applied to Southern Ocean cephalopods.

Try to imagine a lecture hall in King's College filled with zoologists discussing the lives and ways of cephalopods of the Southern Ocean. A few years ago such a dedicated gathering would have been unimaginable for any Southern Ocean invertebrate save for the ubiquitous euphausid, Euphausia superba. How things have changed under the influences of a major international squid fishery and international collaborative research programmes.

No information is available on the embryonic development of Southern Ocean cephalopods. Estimations of developmental times can only be made by extrapolation using data from other geographical areas. Based on known relationships between environmental temperature and embryonic development time, it appears that below 5°C even the smallest squid eggs measuring 0.6–1.0 mm in diameter need one to two months to develop to hatching. At c. 2°C, the embryonic development of these small eggs would probably cover between three and five months. Very large octopod eggs are known to develop over time spans of at least one year. Protection of the developing embryos either by long-lasting capsules laid at appropriate spawning sites, or by active ‘brooding’ (incirrate octopods) is required for embryonic survival and hatching success. The physiological conditions controlling the onset of hatching at very low temperatures are unknown; postponement of hatching appears to be common in cold waters.

Fifteen specimens of Loligo gahi caught within the Falkland Islands Interim Conservation and Management Zone during March 1988 were subject to genetic analysis using horizontal starch gel electrophoresis. Comparison of allele frequencies at 22 clearly resolving putative enzyme loci showed these animals to exhibit a degree of genetic differentiation from samples of Loligo forbesi and Loligo vulgaris vulgaris (I = 0.19 and 0.22 respectively) greater than that normally expected between congeneric species. The degree of difference was of the order typically exhibited between members of different but confamilial genera, for example as here between Loligo forbesi and Alloteuthis subulata (I = 0.22). It is therefore concluded that Loligo gahi should no longer be regarded as a member of the genus Loligo. Genetic analysis of further species is necessary to clarify whether or not Loligo gahi should, as has been suggested on morphological grounds, be united in a separate genus with other American myopsid species also currently ascribed to the genus Loligo.

Cephalopod remains from the stomachs of four pilot whales Globicephala melaena (Traill, 1809), two bottlenose whales Hyperoodon planifrons Flower, 1882 and eight Commerson's dolphins Cephalorhynchus commersonii (Lacepede, 1804) stranded in Tierra del Fuego, Argentina were identified and measured. A total of 3365 lower beaks (mandibles) were identified and measured and from the rostral, crest and hood length, total wet and dry mass, mean mass and mean mantle length for each taxon were estimated. Over 68% of the cephalopods eaten by the pilot whales and all cephalopods eaten by the bottlenose whales were oceanic squid species (oegopsids). The Commerson's dolphins had only eaten shelf species of the families Loliginidae (97.5%) and Octopodinae (2.5%). Sixteen cephalopod families comprising 23 species were represented. In samples from Globicephala melaena, Loligo gahi represented 31% by number and 7.1% by estimated dry mass, Histioteuthis eltaninae, 29% by number and 4.9% by dry mass and the onychoteuthid Moroteuthis ingens 17.2% by number and 51.5% by dry mass. In samples from Hyperoodon planifrons, Histioteuthis eltaninae represented 24.0% of cephalopods by number but only 5.2% by dry mass, Taonius pavo 53% by number but only 2.5% by dry mass and the large onychoteuthid Kondakovia longimana only 2.5% by number but 65.8% by dry mass. In samples from Cephalorhynchus commersonii, the neritic Loligo gahi contributed 97.4% by number and 97% by dry mass and a neritic octopodinid contributed the rest of the cephalopod part of the diet. While the cephalopods contributed the major part of the diets of these particular cetaceans, other remains included fish and polychaete worms.

For many albatross species squid are important prey. Whether albatrosses depend on scavenging (e.g. of vomit from cetaceans, post-spawning die-offs or fishery waste) or on live-capture of squid (e.g. via diel vertical migrations in association with aggregations of squid prey) is controversial. This review of the nature of interactions between squid and the four species of albatross breeding at South Georgia uses data on the foraging range, methods and timing of feeding of the albatrosses in relation to the size, distribution, buoyancy characteristics (floaters or sinkers), bioluminescence and prey of the squid and access to fishery waste. We conclude that most evidence for scavenging needs critical re-evaluation; nevertheless, whereas wandering albatrosses and possibly light-mantled sooty albatrosses probably depend significantly on scavenged squid, black-browed and especially grey-headed albatrosses are unlikely to do so.

Morphometric data were collected for 410 specimens of Pareledone turqueti and P. polymorpha caught around South Georgia. The two species differ in beak morphology and in the male hectocotylus. The species have similar appearances although there is a small but significant difference in the mantle length/body mass relationship for females, with P. polymorpha having a relatively longer mantle. There is no significant difference in the arm length/body mass relationship between species or sexes (p>0.05), except in the case of arm IV of females. There is an interspecific significant difference between sucker number on arms I and II of males, arms I–IV of females, and between hood length and mass of the buccal mass (p<0.05), with P. turqueti having relatively lower sucker numbers, a longer hood length and greater buccal mass mass. The beak of P. turqueti is similar to that of Eledone spp. but P. polymorpha has a small, fine beak with the rostral tip ending in an elongated, sharp point. Differences in beak and buccal mass suggest that these sympatric species occupy distinct trophic niches and that the differing morphology of the male hectocotylus is a factor in reproductive isolation.

A collection of juvenile squid were caught with the Isaacs-Kidd midwater trawl (IKMT) and the Juday plankton net at 86 stations in Prydz Bay (60°–67°30′S, 60°–80°E) to a depth of 500 m but mostly at 0–200 m. Five species were identified, Psychroteuthis glacialis, Alluroteuthis antarcticus, Brachioteuthis sp. and the cranchiids Galiteuthis glacialis and Mesonychoteuthis hamiltoni. P. glacialis and the cranchiids were the most abundant species. Young P. glacialis (5–17 mm ML) were taken at depths of 5–200 m but concentrated in the upper 100 m whilst the cranchiids (5–35 mm ML) occurred over a wider vertical range (50–500 m). The regular occurrence of paralarvae and juveniles suggests that all the species reproduce in the Antarctic. Juvenile Vertical distribution appears to differ between species with P. glacialis concentrated relatively near the surface, the cranchiids in the upper part of the Circumpolar Deep Water and A. antarcticus widely distributed to a depth of 900 m.

Samples of Loligo gahi from the Falkland Islands Interim Conservation and Management Zone collected in March 1987 were analysed to determine the relationships between mass of reproductive and somatic organs during maturation. There was a progressive increase in mass of the reproductive organs with growth in males, while in females these organs did not show a conspicuous increase in mass until a body mass of c. 40 g was reached. No change was found in the mass of the digestive gland in relation to body mass or in the water content of male and female somatic tissues during maturation. Growth of reproductive organs in L. gahi seems to be supported by diet and not at the expense of somatic tissue.

Theory predicts that, in a closed exploited population showing no sampling or other bias, the mean age of fish or squid between one sampling date and the next should increase by the time interval between samples. Age data, derived from statoliths, have been used to test the hypothesis that the effect of migration through an area where a population of Loligo gahi is sampled would be apparent as an increase in mean age per modal group of less than one day per daily time interval between samples. The data show that, in both females and males, the relationship between mean statolith increment number and elapsed time between samples is positive in some months and negative in others. The months in which the relationship between mean increment number and elapsed time is negative are similar to those months in which recruitment has previously been demonstrated to occur, in February, April/May and September for both females and males. Cohorts of squid remain available to the fishery from June–September (females) and February–May and June–July (males) thus allowing mean monthly growth rates of 0.4 mm d−1 for females and 0.7 mm d−1 for males to be calculated. The present study shows that putative age data derived from statoliths apparently demonstrate some sampling biases within a fishery and their effects on the measurement of growth. Migration through the sampled population is manifested by an increase in mean increment number of less than one per day between samples, and growth can only be assessed where the increase in mean increment number is not significantly different from the time elapsed between samples.

The diet and feeding behaviour of Illex argentinus were determined from analysis of stomach contents of squid caught during four bottom trawl surveys carried out over the Bonaerensis (34–40°S, autumn–winter 1991) and Patagonian (45–55°S, summer–autumn 1992) shelves of Argentina. Crustaceans, mainly Themisto gaudichaudii and, to a lesser extent, euphausiids were the most important components of the diet in both areas and years, although there were considerable geographical differences in the relative proportion of the main prey. In the Patagonian area, during summer and autumn of 1992, almost all squid preyed on crustaceans (percentage occurrence = 85.29%), followed by squid (11.76%) and fish (2.94%). On the Bonaerensis shelf, during autumn and winter of 1991, crustaceans were most important by percentage occurrence (56.96%), but fish and squid accounted for a large proportion of the diet (29.41% and 13.62% respectively). Myctophids were prevalent among the fish and cannibalism was on I. argentinus juveniles. Changes in diet composition with squid size demonstrated the opportunistic nature of I. argentinus feeding. Although large squids were able to catch large prey (fish, squid), they also fed on small crustaceans when available, especially in the Patagonian area. The relative abundance of different prey organisms probably determined the diet. In both areas and both years I. argentinus fed mostly during daylight hours, starting in the morning and reaching a maximum in the afternoon. No difference in feeding behaviour was observed between the sexes.

The statolith microstructure was examined from seven species of seven families of Antarctic squid captured in Prydz Bay (n=23). Five of the species (Kondakovia longimana, Psychroteuthis glacialis, Brachioteuthis sp., Mastigoteuthis psychrophila, Galiteuthis glacialis) had very clear statolith growth increments which could be enumerated from the nucleus to the statolith margin. These increments were similar in appearance to daily statolith increments in other temperate and tropical squids. Psychroteuthis glacialis also had two distinct zones which may reflect growth during the pelagic and demersal phases of the life cycle. Total statolith increment counts were not possible on two of the species (Bathyteuthis abyssicola and Alluroteuthis antarcticus). The statolith microstructure of Bathyteuthis abyssicola had some very faint increments near the nucleus but increments were not visible in most of the statolith microstructure, while the statolith microstructure of A. antarcticus was indistinct in the nuclear region (possibly due to the formation of a second primordium during ontogenesis). Future research may reveal that statolith increments are useful tools for Antarctic squid age and growth studies.

Allozyme differentiation was investigated at 23 putative enzyme coding loci in 16 ommastrephid squids to identify species and to assess genetic relationships. The species examined were Illex illecebrosus, I. coindetii, I. argentinus, Todaropsis eblanae, Todarodes sagittatus, T. angolensis, T. filippovae, T. pacificus pacificus, Nototodarus sloanii, N. gouldi, Martialia hyadesi, Ommastrephes bartramii, Sthenoteuthis pteropus, S. oualaniensis, Eucleoteuthis luminosa, and Dosidicus gigas. A dendrogram based on Nei's genetic distance between the species closely approximates to the latest systematics based on morphological characters, but the positions of M. hyadesi and T. eblanae were considerably distant from all other species. The results demonstrate the benefits of further biochemical analysis to an understanding of the systematics of the ommastrephid squids.

Fortyfour octopods from bottom trawls off Palmer Archipelago, south-eastern Argentina, south-eastern New Zealand, Crozet Islands and Showa Station were examined. Three species of Pareledone, three species of Graneledone and one species of Megaleledone were identified. All were characterized by having a single row of arm suckers. Mature males of P. harrissoni, P. adelieana and G. macrotyla were recorded for the first time. Hectocotylus and male reproductive organs of these species are described. On the basis of previously reported distributions and the present localities, P. charcoti, P. harrissoni and P. adelieana appear to have circumantarctic distributions. G. macrotyla was identified but the other two species of Graneledone could not be identified to species level because of the poor systematic state of this genus.

It appears that squid statoliths cannot yet be regarded as accurate an ageing tool as fish otoliths. Statoliths from the same pair, prepared differently for viewing and counting increments, were compared. Increment counts do not imply age in days, because this was not validated. One statolith from each pair was examined by light microscopy (LM) after preparation following a new method. The other was viewed by Scanning Electron microscopy (SEM) with a modified etching solution. Shape of each statolith was similar when compared by multiple regression analysis (11 variables, n=53). There was a weak but significant difference between sexes (statoliths of females were slightly larger). All other differences were insignificant. Microscopic observation and increment counts of increments were successfully carried out for 37 pairs of statoliths. Significant differences between two independent counts were found for the LM method, but no significant differences were found between two independent SEM counts. Counts were significantly different when interpreted by both LM and SEM, probably because of poor resolution in the LM readings and over-resolution (growth layers prominent and numerous) in those read by SEM. Recommendations are made on how ageing studies, based on statoliths, should be structured and the results evaluated.

The teuthoid fauna of the Prydz Bay region of the Southern Ocean (Indian Ocean sector) has been studied based on the material collected from 1981–1991 using a rectangular midwater trawl (RMT-8), pelagic trawl (IYGPT), and bottom trawl. Eight species of squid have been recognized: Brachioteuthis sp., Kondakovia longimana, Bathyteuthis abyssicola, Psychroteuthis glacialis, Alluroteuthis antarcticus, Mastigoteuthis psychrophila, Mesonychoteuthis hamiltoni and Galiteuthis glacialis. Size frequency distribution, geographical and vertical distributions of each species as well as diets of common species are analysed. There is no evidence of a diel vertical migration but ontogenetic descent appears to occur in P. glacialis and G. glacialis. Antarctic krill, Euphausia superba and the Antarctic silverfish, Pleuragramma antarcticum are important prey for most species with cannibalism occurring in P. glacialis, A. antarcticus and M. hamiltoni. Equations for calculating total weight from mantle length, and mantle length and total weight from upper and lower rostral length are provided for B. abyssicola, P. glacialis, A. antarcticus, M. psychrophila, and G. glacialis.

Two specimens of Kondakovia longimana were recently obtained from the Indian Ocean sector of the Southern Ocean. One specimen, damaged but near the known maximum size, was found floating on the surface, and the other, a male subadult specimen, was captured by a pelagic trawl. Examination of the specimens, histological sections and analyses of tissue samples revealed that the muscular tissues of the tentacular stalks and the mantle contain a large amount of ammonium, more than 328 mM, a quantity that far exceeds that of Moroteuthis ingens (206.9 mM) and Moroteuthis robsoni (199.6 mM) from the South Tasman Rise. Catch data and published records suggest that the juveniles and subadults of K. longimana feed on krill in the epipelagic zone.

The relatively small numbers of pelagic cephalopods caught in the RMT-8 samples (0–300 m) in February/March 1983 in the Weddell Sea were dominated by early life stages of the cranchiid squid Galiteuthis glacialis. A total of 48 specimens were caught with dorsal mantle length (ML) ranging from 4–36 mm. They occurred with a mean density of 0.15 ind. × 1000 m−3 and were present in 38% of 33 RMT-8 samples. G. glacialis was the only cranchiid squid found in the Weddell Sea between 66° and 74°S. Its early life stages were concentrated in the layers below the summer thermocline (>50 m) and body sizes appeared to increase towards deeper water layers. For biochemical analyses, nine specimens of G. glacialis (ML 6–18 mm) were sampled in the eastern Weddell Sea between 185–520 m water depth in January/February 1985. Total lipid contents ranged from 8%–11% dry weight (DW) with phospholipids being the main lipid component (43–56% of total lipid). Storage lipids (triacylglycerols) made up 18–26% of total lipid. The relatively low lipid contents may reflect the early development stage of the specimens examined. The data presented give the first information on geographical and vertical distribution patterns of early life stages of G. glacialis in the high-Antarctic Weddell Sea, as well as on their lipid content and composition.

The data presented provides new information on the distribution of Antarctic squids and on the summer diet of the emperor penguins. The diet of 58 adult emperor penguins (Aptenodytes forsteri) on the fast ice of the Drescher Inlet, Vestkapp Ice Shelf (72°52′S, 19°25′W) in the eastern Weddell Sea was investigated. Prey consisted principally of squid, fish, krill, amphipods and isopods. Squids were identified by the lower beaks and allometric equations were used to estimate the squid biomass represented. Beaks occurred in 93% of the stomach samples. Each sample contained a mean of 27 beaks (range 1–206). Ninety-two percent of the squids could be identified by the lower beaks and belonged to four families (Onychoteuthidae, Psychroteuthidae, Neoteuthidae and Gonatidae). The most abundant squid was Psychroteuthis glacialis which occurred in 52 samples with lower rostral lengths (LRL) ranging from 1.4–7.2 mm. Forty-five samples contained Alluroteuthis antarcticus (LRL range 1.8–5.8 mm), 17 Kondakovia longimana (LRL range 4–12.1 mm), and four Gonatus antarcticus (LRL range 4.1–6.1 mm). In terms of biomass K. longimana was the most important species taken by the penguins comprising 50% of total estimated squid wet mass (245348 g) in 1990 and 48% in 1992 (154873 g). However, if only fresh beaks were considered for estimations of squid consumption, i.e. beaks that have been accumulated for not longer than 5–6 days in the stomachs, squid diet was of minor importance. Then total squid wet mass accounted for only 4809 g in 1990 and 5445 g in 1992 which implies that one penguin took c.30 g squid d−1 with P. glacialis and A. antarcticus being the most important by mass. The prey composition suggests that emperor penguins take squid at the steep slope regions of the eastern Weddell Sea.