Family GONATIDAE

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Family GONATIDAE

Compiler and date details

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

Introduction

Members of the family Gonatidae Hoyle, 1886 are medium sized oceanic squid, with a narrow mantle and large rhomboidal or heart-shaped fins. They are common in the temperate and cold regions of both hemispheres and particularly well represented in the boral region of the North Pacific. Worldwide three genera with some 19 nominal species are known (Young 1972; Nesis 1987; Okutani & Clarke 1992). Only Gonatus antarctica Loennberg, 1898 is known from Australian waters—from off Macquarie Island.

Gonatids are oceanic, but are encountered in continental slope waters off Macquarie Island where they are caught in demersal trawls. In the North Pacific, Gonatus fabricii feeds on a broad range of fish, crustaceans—including copepods, euphausids and amphipods, pteropods and chaetognaths, and are at least partly cannibalistic (Rodhouse & Nigmatullin 1996). Known predators include cod and tunas, whales, seals and gulls (Nesis 1965; Clarke 1966a, 1996b; Croxall & Prince 1996; Klages 1996; Smale 1996). In the Australian Antarctic Territory waters, predators of Gonatus antarctica include the Emperor Penguin (Gales et al. 1990) and the Patagonian toothfish, Dissostichus eleginoides off Macquarie Island (Lu, unpublished data).

Gonatid reproductive organs are typically oegopsid. Hectocotylisation has not been observed in any males, and the spermatophores are transferred into the mantle cavity (Berryteuthis) or onto the buccal membrane of the female (Gonatus and Gonatopsis) (Nesis 1987).

Little is known about longevity or growth of gonatids. Kristensen (1980) studied the pen length and growth lines in statoliths of Gonatus fabricii and found daily gowth lines. Kristensen (1980) calculated that specimens of about 100 mm pen length were one year old and that two year-classes were found in G. fabricii in West Greenland waters.

Diagnosis

Members of the family Gonatidae are medium sized squid with a narrow, muscular to semigelatinous mantle and large rhomboidal or heart-shaped fins. The arms are equipped with 4 rows of suckers (8-12 rows at arm tips in Gonatopsis). In adults, the 2 median rows of suckers on the 1st to 3rd arms are modified to form hooks (in Berryteuthis anonychus the hooks are present only in females and in small numbers). The tentacular club is long and wide (in Gonatopsis tentacles are present only in larvae-absent in adults), bearing many rows of suckers that are sometimes strongly differentiated in size, 1 or 2 large and sometimes several small hooks may develop in the central part of club (in Gonatus only). The funnel locking cartilage is simple, linear and the buccal connectives attach to the ventral border of the ventral arms. Photophores are known to be present only on eyes in one species. There is no hectocotylised arm in males.