Glass squid

From Wikipedia, the free encyclopedia

iGlass squid

Cranchiid squid juvenile found in plankton, Antarctica

Scientific classification

Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Coleoidea
Order:	Teuthida
Suborder:	Oegopsina
Family:	Cranchiidae Prosch, 1847

Genera

about 15, see text

The family Cranchiidae comprises the approximately 60 species of glass squids, also known as cranchiid or cranch squids. Cranchiid squids occur in surface and midwater depths of open ocean around the world. They range in body size from 10 cm to 2 m. The common name, glass squid, derives from the transparent nature of most species. Cranchiid squids spend much of their lives in partially sunlit shallow waters where their transparency provides camouflage. They are characterised by a swollen body and short arms, which bear two rows of suckers or hooks. The third arm pair is often enlarged. Many species are bioluminescent organisms and possess light organs on the undersides of their eyes, used to cancel their shadow on the sea floor. Eye shape varies widely, ranging from large and circular to telescopic and stalked. A large fluid-filled chamber containing ammonia solution is used to aid buoyancy. Often the only organ that is visible through the transparent tissues is a cigar-shaped digestive gland, which is the cephalopod equivalent of a mammalian liver. This is usually held in a vertical position to reduce its silhouette and a light organ is sometimes present on the lower tip to further minimise its appearance in the water.

Like most squids, the juveniles of cranchiid squids live in surface waters, descending to deeper waters as they mature. Some species live over two kilometres below sea level. The body shape of many species changes drastically between growth stages and many young examples could be confused for different species altogether.

Cranchiid squids are not harvested commercially by any fisheries.