Subclass COLEOIDEA Bather, 1888

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Introduction

Nine living Orders have been recognised: Bathyteuthida, Idiosepida, Myopsida, Oegopsida, Sepiida, Sepiolida, and Spirulida in the Superorder Decapodiformes and Octopoda and Vampyromorpha in the Superorder Octopodiformes (WoRMS, 2024). All are represented in Australian waters.

Diagnosis

Shell internal, chitinous, rarely calcareous, occasionally absent. Mantle muscular, but in deepwater forms the musculature degenerates and is replaced by gelatinous connective tissue. Chromatophores well developed and complicated. Photophores often present. Eyes large, complicated with a lens, iris, cornea, and vitreous body. Statocysts highly developed. Osphradia absent. Four or 5 pairs of muscular appendages with suckers that are often equipped with chitinous rings. Hectocotylisation affects one or two arms of the male in many species. Funnel a muscular conical tube except in deepwater species; funnel organ present. Fast-swimming forms also equipped with a funnel valve. Mantle either fused with head or funnel or joined to them by a system of cartilages. Beak strong and well developed. Radula with 7 longitudinal rows of teeth (one genus with 5 rows) in most forms. Radula reduced or absent in some planktophagous forms, mainly from deepwater. One pair of gills, 2 auricles, 2 renal sacs, and 2 branchial hearts. Ink sac present or absent. Nervous system highly developed, with a compact brain consisting of several ganglia and lobes. Stellate ganglion well developed. Nektonic forms have a system of giant nerve fibers innervating the mantle muscles. Gonad unpaired; male genital ducts generally unpaired (paired in rare cases) and in females may be paired or unpaired. Eggs small or large. (Modified from Nesis, 1982).

Five living orders are recognised: Sepiida, Sepiolida, Teuthida, Vampyromorpha, and Octopoda.

General References

Nesis, K.N. 1982. Cephalopods of the World. English Translation from Russian. Levitov, B.S. (Transl.), Burgess, L.A. (ed.) (1987) Neptune City : T.F.H. Publications, Inc. 351 pp. [English Translation from Russian]

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