# Cranchiidae

The family Cranchiidae comprises the approximately 60 species of glass squid, also known as cockatoo squid, cranchiid, cranch squid, or bathyscaphoid squid. Cranchiid squid occur in surface and midwater depths of open oceans around the world. They range in mantle length from 10 cm (3.9 in) to over 3 m (9.8 ft), in the case of the colossal squid. The common name, glass squid, derives from the transparent nature of most species. Cranchiid squid 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 that bear two rows of suckers or hooks. The third pair ofarms is often enlarged. Many species are bioluminescent organisms and possess light organs on the undersides of their eyes, used to cancel their shadows. Eye morphology varies widely, ranging from large and circular to telescopic and stalked. A large, fluid-filled chamber containing ammonia solution is used to aid buoyancy. This buoyancy system is unique to the family and is the source of their common name "bathyscaphoid squid", after their resemblance to a bathyscaphe. 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 squid, the juveniles of cranchiid squid live in surface waters, descending to deeper waters as they mature. Some species live over 2 km 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.
The largest squid in the family Cranchiidae is the colossal squid.
Cranchiid squid are of no interest to commercial fisheries.
The family is named for John Cranch.

## Behavior
### Diet

Cranchiids occupy a variety of trophic levels, with some species relying heavily on mesopelagic crustaceans and small fishes. Recent research using fatty acid and stable isotope analyses has shown that smaller cranchiids in the Benguela Upwelling System feed at mid to lower trophic levels, whereas larger, more muscular squid families occupy higher trophic positions. Early juveniles may also exploit rich surface waters for faster growth before transitioning to deeper zones.

### Migration

As they develop, glass squids often exhibitt a two-phase life cycle: juveniles in the epipelagic layers, then migrating into bathypelagic waters as adults. By remaining translucent and harnessing specialized buoyancy mechanisms involving ammonia retention, cranchiids reduce energy expenditure and adapt to low-light deep-sea habitats. This vertical migration strategy is thought to minimize predation risk while maximizing feeding opportunities.

## Genera

The family contains two subfamilies (both established by Georg Johann Pfeffer) and about 15 genera:
* Subfamily Cranchiinae
** Genus Cranchia
** Genus Leachia
** Genus Liocranchia
* Subfamily Taoniinae
** Genus Bathothauma
** Genus Belonella
** Genus Egea
** Genus Galiteuthis
** Genus Helicocranchia
** Genus Liguriella
** Genus Megalocranchia
** Genus Mesonychoteuthis
** Genus Sandalops
** Genus Taonius
** Genus Teuthowenia
* Parateuthis tunicata (incertae sedis)
The genus listed above with an asterisk (*) is questionable and needs further study to determine if it is a valid genus or a synonym.