Family CRANCHIIDAE

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Family CRANCHIIDAE

Compiler and date details

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

Introduction

The diverse family Cranchiidae Prosch, 1849 consists of small to very large (more than 1 m mantle length (ML)) oceanic squid displaying a high degree of morphological diversity. All members of the family have the mantle fused to the head in the nuchal region and to the funnel at its two posterior lateral corners.

The 13 currently recognised genera are divided between two subfamilies, Cranchiinae Prosch, 1849 and Taoniinae Pfeffer, 1912. Cranchiines are characterised by the presence of one or two cartilaginous strips extending posteriorly from the anterior apex of the funnel-mantle fusions and the fusion of the funnel to the head laterally; four or more small round or oval photophores are present on the eyes, and the right or left ventral arms are hectocotylised in mature males. Taoniines lack cartilaginous strips and the funnel is free from the head laterally; one to three dissimilar-sized crescent-shaped light organs are present on the eyes and hectocotylisation is absent. Secondary sexual modification of the ends of the arms in mature males, and development of brachial end-organs on the arms of mature females, may be present in both subfamilies.

Cranchiids were first recorded from eastern Australian waters by Allan (1940, 1945) with 'Pyrgopsis pacificus Issel, 1908' (probably Leachia sp.) the most numerous cephalopod in her plankton collections. Brandt (1983) recorded at least five cranchiid species from both subfamilies from a warm-core eddy of the East Australian Current. Lu & Phillips (1985) list at least 13 species and species groups from off the east coast.

Taxonomic confusion in the family was partially a consequence of the major morphological changes that accompany growth in many cranchiids. The confusion has been resolved partially by the work of N. Voss (1980, 1985). Early larval characters such as stalked eyes and paddle-shaped fins are lost or modified at varying stages during growth in each genus (Clarke 1966; N. Voss 1980, 1985; Rodhouse & Clarke 1986). Where known, the cranchiid reproductive systems show typical oegopsid characteristics with the exception of the four nidamental glands reported by G. Voss (1962) for a female of Ascocranchia joubini from the North Atlantic. Females have no spermathecae. In Teuthowenia pellucida (Chun), a species abundant in eastern Australian waters, spermatophores are embedded externally on the anterior half of the mantle, either dorsally or ventrally. The sperm reservoirs penetrate the inner wall and release sperm into the mantle cavity where, apparently, fertilisation of mature eggs occurs as they leave the oviducal glands. The presence of large swollen nidamental glands in mature females suggests that the eggs are deposited in one or more gelatinous egg masses. An estimated 6000 to 8000 eggs of 3.0 mm maximum length were carried by two mature female T. pellucida of 177 and 187 mm ML (N. Voss 1985).

Little is known on the life history of cranchiids. Available information on Teuthowenia megalops (Prosch) from the North Atlantic was reviewed by Nixon (1983). N. Voss (1985) concluded that female T. pellucida probably shed all their eggs over a short period and do not survive beyond one spawning period. Males may mate more than once, but like the females, do not survive past one limited mating season. No information on the life span and growth rates of any cranchiid species is available currently. Cranchiids form a minor part of the diet of sperm whales off south-western Australia and in the Tasman Sea (Clarke 1980; Clarke & MacLeod 1982) and are also components of the diets of lancetfish and yellowfin tuna from the Coral Sea and north-eastern Indian Ocean (Rancurel 1970, 1976; Fujita & Hattori 1976); they are also eaten by seabirds (Imber 1978), blue sharks (Clarke & Stevens 1974), albacore tuna and dolphins (Clarke 1966).

Cranchiids show ontogenetic descent. The smallest larvae of Teuthowenia pellucida are more abundant in the upper 600 m, while those metamorphosing to the subadult stage are predominant at depths of 700 to 800 m. Adults generally occur below 500 m and as deep as 2400 m. Mature T. pellucida have only been caught in water depths of more than 3800 m (N. Voss 1985). Off Hawaii Leachia pacifica (Issel, 1908) lives in near-surface waters until it reaches about 80% of its maximum length; both males and females then descend to depths up to 2300 m where they mature, mate and then, apparently, spawn (Young 1975). Diel vertical migration of larval or adult cranchiids has not been demonstrated conclusively beyond Australia (Roper & Young 1975; Young 1975).

Cranchiids are among the most speciose and abundant of oegopsid squid and occur in all oceans from the surface to depths in excess of 3500 m. Of the 13 genera recognised by N. Voss (1980), eight are known from Australian waters although none is endemic. The distribution of most species in Australian waters is poorly known. N. Voss (1985) concluded that Teuthowenia pellucida is distributed circumglobally in the mixed waters of the Subtropical Convergence, its local occurrence affected by surface winds, currents and bottom depth.

An Australian specimen of Teuthowenia pellucida was included in the molecular study of FERNÁNDEZ-ÁLVAREZ et al. (2022).

Diagnosis

The family is characterised by having the mantle fused to the head in the nuchal region and to the funnel at its two posterior lateral corners. The arms generally bear biserial, sharp-toothed suckers, and the armature of the tentacular clubs (suckers, hooks or hook-like suckers) is generally quadriserial. Buccal connectives attach to the ventral borders of the ventral arms and photophores are present on the eyes and on the arm tips in some species.