Family CHIROTEUTHIDAE

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Family CHIROTEUTHIDAE

Compiler and date details

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

Introduction

Members of the family Chiroteuthidae Gray, 1949 are small to medium sized squid (less than 400 mm mantle length (ML)) with somewhat gelatinous bodies. Worldwide over 12 nominal species have been described in three genera, Asperoteuthis, Chiroteuthis and Planctoteuthis; only Chiroteuthis has been recorded from Australian waters. The taxonomy of the family is thoroughly confused and in need of revision.

Chiroteuthis sp. was reported from among the stomach contents of lancetfish from the south-western Pacific and north-eastern Indian Ocean by Rancurel (1970) and Fujita and Hattori (1976). Nesis (1979) recorded Chiroteuthis picteti from the Australasian Region and Brandt (1983) caught a Chiroteuthis species inside a warm-core eddy of the East Australian Current. Two species, C. imperator Chun and an unspecified Chiroteuthis species, are listed by Lu & Phillips (1985) from the Tasman Sea and off north-western Australia. At least one futher species is known to exist in museum collections (Lu, unpublished data).

Chiroteuthids have a distinctive larval form, the doratopsis, which attains an unusually large size (up to 60 mm ML in some species). This larva has an elongate spindle-shaped mantle, almost circular fins and the gladius projecting posteriorly as a narrow rod. The head is attached to an extraordinarily long transparent neck. Unlike that of Brachioteuthis larvae, the chiroteuthid neck has many membranous partitions. Clarke et al. (1979) concluded that the neck region provides buoyancy for the whole animal. In smaller specimens, the tentacles and the ventral arms are approximately equal in length and very long (up to 60% of the mantle length). The remaining arms are poorly developed. Light organs are not readily apparent in the larval stages. Growth is allometric in post larval stages, the head becoming shorter through loss of the post-orbital neck, the mantle relatively wider and the fins, while maintaining their relative length, becoming relatively wider. The advanced development of the ventral arms seen even in larval stages is maintained with growth, these structures contributing the major component of the buoyancy of adult chiroteuthids. It is likely that adults float with the ventral arms uppermost (Clarke et al. 1979). In some species the tail is lost, while in others a cylindrical gelatinous projection is retained.

Little is known of chiroteuthid life histories. The broad size distribution of specimens of Chiroteuthis imperator examined by Kubota et al. (1981) is perhaps indicative of an extended spawning season for this species in Japanese waters. No information on the life span or growth rate of any chiroteuthid species is currently available. Chiroteuthids form part of the diet of sperm whales off south-western Australia and in the Tasman Sea (Clarke 1980; Clarke & MacLeod 1982); of lancetfish and yellowfin tuna in the Coral Sea and north-eastern Indian Ocean (Rancurel 1970, 1976; Fujita & Hattori 1976); and of oceanic sharks off eastern Australia (Dunning et al. 1993). Off Japan, C. imperator feeds on micronektonic crustaceans, molluscs and fish (Kubota et al. 1981).

From their numerical abundance among sperm whale stomach contents, Clarke (1980) concluded that off southern Africa C. joubini Voss forms schools although whether this behaviour is characteristic of other members of the family is not known. Chiroteuthis species have been shown to display ontogenetic descent, the smallest larvae most abundant in the upper 100 m and those metamorphosing to the subadult stage predominating at depths of 500 to 700 m. Adults apparently occur below 500 m by day but are distributed throughout the water column during the night. Diel vertical migration of larvae and adults is also evident in some species (Roper & Young 1975).

The distribution of this family in Australian waters is poorly known. Chiroteuthis picteti is considered to be restricted to oceanic waters north of 30°S in the Australasian region by Nesis (1979). Chiroteuthis imperator has been taken in bottom trawls in continental slope waters (300 to 600 m) off the North West Shelf.

Diagnosis

Chiroteuthids are characterised by an oval funnel locking apparatus with one or two knobs projecting towards the centre of the cavity. The arms, including the greatly enlarged ventral pair, bear biserial, toothed suckers. The tentacles are very elongate (up to five times the mantle length) and bear distinctive clubs with tetraserial suckers on long stalks. Buccal connectives attach to the ventral borders of the ventral arms. In most species abundant photophores are present along the tentacle stalks and the ventral arms. Large light organs are also present ventrally on the eyes, at the tips of the tentacular clubs and embedded in the ink sac on both sides of the intestine in most species.