Myopsina

Myopsina
Eye of myopsid squid showing corneal membrane and lack of secondary eyelid
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Order:	Teuthida
Suborder:	Myopsina d'Orbigny, 1841
Families
Australiteuthidae Loliginidae

Myopsina is a suborder of squid containing two families: the monotypic Australiteuthidae and the diverse and commercially important Loliginidae (~50 species). Some taxonomists raise this group to the level of an order, in which case it is known as Myopsida. This is due to Myopsina and Oegopsina not being demonstrated to form a clade.

A number of morphological features distinguish members of Myopsina from those of its sister group, Oegopsina. Some of the most obvious differences are found in the structure of the eyes: those of myopsid squids lack a secondary eyelid and are instead covered by a transparent corneal membrane, the opening of which is reduced to a microscopic anterior pore in most species. The arms and tentacles are ornamented with simple suckers (hooks are never present), with additional suckers usually borne on the buccal lappets. The carpal ("wrist") portion of the tentacular club lacks a locking apparatus, and a tentacle pocket is present on the head. The funnel has no lateral adductor muscles. An internalised shell is present in the form of a well-developed gladius, which is located dorsally within the mantle and extends for almost its entire length. In contrast to oegopsids, females possess accessory nidamental glands in addition to the main nidamental glands. They however lack a right oviduct.^[1][2]

Myopsids are found in coastal waters worldwide. They are demersal, generally feeding on or near the bottom.^[1][2]

Adult sizes range from the dwarf Australiteuthis and Pickfordiateuthis, whose males mature at less than 2 cm (0.79 in) in mantle length (ML), to the large Loligo forbesii, which can exceed 90 cm (3.0 ft) ML.^[1][2]

References