Family OMMASTREPHIDAE

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Family OMMASTREPHIDAE

Compiler and date details

C.C. Lu, National Chung Hsing University, Taichung, Taiwan

Introduction

Squid of the family Ommastrephidae Steenstrup, 1857 are medium to large sized (more than 500 mm mantle length (ML)), with a strong muscular torpedo-shaped mantle. Three subfamilies, Ommastrephinae, Todarodinae and Illicinae, are recognised on the basis of the presence and structure of some skin folds (the foveola and side pockets) in the funnel groove. Twenty-one species and one subspecies are known worldwide. Ten species, belonging to all subfamilies, are represented in Australian waters (Lu & Dunning 1982; Lu & Phillips 1985).

McCoy described Ommastrephes gouldi, the first ommastrephid from Australian waters, in 1888. Brazier (1892) listed two additional species, O. gigas d'Orbigny and O. oualaniensis Lesson, the first of which was a misidentification as the species occurs only in the eastern Pacific. Nesis (1979) provided records of additional species from the Australasian region. The most recent checklist of Australian ommastrephids is that of Lu & Phillips (1985).

Nototodarus Pfeffer, Todaropsis Girard and Todarodes Steenstrup typically display a dark, narrow mid-dorsal stripe on the mantle, replaced in oceanic species by a general darkening of the dorsal surface. Large light organs, either oval or as stripes, are present in Sthenoteuthis Verrill, Eucleoteuthis Berry and Hyaloteuthis Gray, ventrally or dorsally on the mantle and/or ventrally on the head and bases of the ventral arms. Juveniles of these species have oval light organs ventrally on the eyes and between the ink sac and intestine (Dunning 1985). Adult Ornithoteuthis Okada have an additional luminous stripe mid-ventrally along the viscera. In Ommastrephes d'Orbigny, small subcutaneous light organs are distributed ventrally on the mantle and head (Lu & Dunning 1982).

All ommastrephids are active predators, grasping their prey with the arms and tentacles which bear suckers carrying sharp, strongly developed conical teeth on the chitinous sucker rings, and dividing the victim using the heavily chitinised beaks. All species in Australian waters have buccal seminal receptacles for storage of sperm bulbs during copulation. The presence of sperm bulbs in the spermathecae of immature females of several species suggests that copulation may precede spawning by some time in this group. The family has a distinct larval form, the rhynchoteuthion, characterised by fusion of the tentacles until a size of 5–10 mm ML is reached, when separation occurs.

From examination of population size structure, it appears probable that most species in Australian waters reach reproductive maturity at less than two years of age, reproduce for a single season only and die. In some species, males mature at considerably smaller sizes than females. Spawning locations are unknown although larvae have not been found beyond continental shelf/slope waters.

Members of this family occupy all major marine habitats on the tropical and temperate continental shelf, continental slope and in oceanic waters. They feed on a broad range of crustaceans, fish, other pelagic molluscs and squids, and are at least partially cannibalistic (O'Sullivan & Cullen 1983). Known predators include seabirds, teleosts and sharks, whales, dolphins and seals (Dunning & Brandt 1985). Ommastrephids are schooling species, school size decreasing as the animal grows. Evidence from commercial fishing operations suggests that neritic species congregate close to the bottom during the day, moving up through the water column at night. Oceanic species have been seen feeding at the surface at night—large Ommastrephes have been observed hunting, perhaps cooperatively, for prey. Juveniles of several species are able to glide, like exocoetid flying fish, for distances in excess of 10 m, to escape predators. There is evidence for long distance migrations elsewhere in the world by Ommastrephes associated with spawning (Dunning & Brandt 1985), and perhaps on a smaller scale for Nototodarus in southern Australian (H. Smith 1983) and New Zealand waters (Sato 1985).

With the exception of polar waters, ommastrephid squid occur in all oceans. Of the 11 genera recognised worldwide, nine occur in Australian waters and one subspecies appears to be endemic. Significant distributional overlap occurs for many species, particularly in East Australian Current waters where juveniles of up to five genera have been taken in the same trawl catch (Dunning & Brandt 1985). Todarodes pacificus pucillus Dunning, 1988 occurs in continental shelf waters north of 27°S. The genus Nototodarus is represented in northern slope waters by N. hawaiiensis (Berry) and in shelf waters south of 25°S by N. gouldi. The distribution of the former species overlaps with that of the less abundant Todaropsis eblanae (Ball). Ornithoteuthis volatilis (Sasaki) is commonly caught in trawl catches from slope waters between 18° and 35°S. Occasionally the Subantarctic shelf species, Martialia hyadesi Rochebrune & Mabille, has been found stranded on the beach after storms at Macquarie Island, sometimes in large numbers. Dunning (1988) reviewed the distribution of arrow squids off eastern Australia.

Hyaloteuthis pelagica (Bosc) occurs in tropical and Eucleoteuthis luminosa (Sasaki) in subtropical oceanic waters off the east coast. Ommastrephes bartrami is the dominant ommastrephid in the south-eastern Indian Ocean and Tasman Sea north of 40°S, replaced to the south by Todarodes filippovae Adam. This species is also caught in continental slope waters around the southern Australian coast.

Excluded Taxa

Misidentifications

OMMASTREPHIDAE: Dosidicus gigas Brazier, 1892 — Lu, C.C. & Phillips, J.U. 1985. An annotated checklist of Cephalopoda from Australian waters. Occasional Papers of the Museum of Victoria 2: 21-36 [31]

OMMASTREPHIDAE: Dosidicus Steenstrup, 1857

Diagnosis

The family is characterised by an inverted T-shaped funnel locking cartilage, biserial suckers on the arms and, in all Australian representatives, tetraserial suckers on the tentacular clubs. The buccal connectives attach to the dorsal border of the ventral arms and light organs are present in some genera. One or both ventral arms in males are hectocotylised.