Family OCTOPOTEUTHIDAE

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Family OCTOPOTEUTHIDAE

Compiler and date details

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

Introduction

The family Octopoteuthidae Berry, 1912 includes two genera, Octopoteuthis and Taningia, of medium to large squid (up to more than 1000 mm mantle length (ML)) characterised by a broad, straight funnel locking apparatus and very broad fins extending almost the length of the mantle. Seven nominal species of Octopoteuthis and one species of Taningia are known. One species from each genus has been reported from Australia. Species characteristics within the genus Octopoteuthis are poorly defined; the genus is badly in need of revision (Lu & Phillips 1985).

The genus Octopoteuthis was first recognised from the south-western Pacific by Rancurel (1970). Nesis (1979) also reported occurrence of Taningia danae in the Australasian region. Clarke (1980) provided further records of octopoteuthids from stomach contents of sperm whales off Albany, Western Australia, and Zeidler (1981) reported large moribund Taningia danae from off South Australia.

Larval Octopoteuthis body proportions change rapidly during growth up to 15 mm ML. Eyes which initially appear stalked become sessile at ML of 10 to 15 mm and most specimens also lose their tentacles by this size (Stephen 1986). The mantle of some Octopoteuthis species has a thick gelatinous layer lying external to the pigmented skin-like layer; it is especially thick over the tail region. Clarke (1980) suggested that the presence of longitudinal grooving in the anterior mantle jelly is characteristic of females in at least one species and that this region is where spermatophores are lodged by the males. Clarke (1967) estimated that a female Taningia of 1400 mm ML carries 250 000 ovarian eggs. Life histories are largely unknown for the family.

Octopoteuthids form a significant component of the sperm whale diet off south-western Australia and in the Tasman Sea (Clarke 1980; Clarke & MacLeod 1982), and are also eaten by lancetfish in the Coral Sea (Rancurel 1970) and oceanic sharks off eastern Australia (Dunning et al. 1993).

From their numerical abundance in individual sperm whale stomachs, Clarke (1980) concluded that Octopoteuthis rugosa Clarke, 1980 is a schooling species, but that Taningia species may be solitary or form small groups only. Ontogenetic descent may occur in Taningia, as small specimens occur in the upper 200 m, and adults are more abundant in depths of more than 1000 m (Clarke 1967). According to Roper & Young (1975), larval Octopoteuthis off California are distributed in a narrow depth band from 200 to 400 m during the day, spreading throughout the upper 500 m at night. However, Stephen (1986) was unable to find conclusive evidence of diel variation in the depth distribution of Octopoteuthis larvae collected primarily from the North Atlantic.

Diagnosis

Octopoteuthids are characterised by a broad, straight funnel locking apparatus and very broad fins extending almost the length of the mantle. The genus Octopoteuthis has biserial hooks on the arms, and sometimes small biserial suckers at their tips. The tentacles in all larvae bear a few distal club suckers which are lost in adults. Buccal connectives attach to the ventral borders of the ventral arms. Several small, spindle-shaped photophores are present on the tips of all eight arms in the genus Octopoteuthis, and a single very large photophore occurs at the tip of each dorso-lateral arm in the monotypic genus Taningia. Hectocotylisation in males is absent.