Glass squid
Encyclopedia
The family Cranchiidae comprises the approximately 60 species of glass squid, also known as cranchiid or cranch squid. Cranchiid squid occur in surface and midwater depths of open oceans around the world. They range in mantle
length from 10 centimetres (3.9 in) to over 3 metres (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, 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 eye
s, used to cancel their shadow. 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
. Often the only organ
that is visible through the transparent tissues is a cigar-shaped digestive
gland
, which is the cephalopod
equivalent of a mammal
ian 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 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 squid represent no interest to commercial fisheries
.
The genus listed above with an asterisk (* ) is questionable and needs further study to determine if it is a valid genus or a synonym.
Mantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
length from 10 centimetres (3.9 in) to over 3 metres (9.8 ft), in the case of the Colossal Squid
Colossal Squid
The colossal squid , sometimes called the Antarctic or giant cranch squid, is believed to be the largest squid species in terms of mass. It is the only known member of the genus Mesonychoteuthis...
. 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
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
. They are characterised by a swollen body and short arms, which bear two rows of suckers or hooks. The third arm
Cephalopod arm
A cephalopod arm is distinct from a tentacle, though the terms are often used interchangeably.Generally, cephalopod arms have suckers along most of their length, as opposed to tentacles, which have suckers only near their ends. Octopuses have eight arms and no tentacles, while squid and cuttlefish...
pair is often enlarged. Many species are bioluminescent
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
organisms and possess light organs on the undersides of their eye
Cephalopod eye
Cephalopods, as active marine predators, possess sensory organs specialized for use in aquatic conditions. They have a camera-type eye, which consists of a lens projecting an image onto a retina. Unlike the vertebrate camera eye, the cephalopods' form as invaginations of the body surface , and...
s, used to cancel their shadow. Eye morphology varies widely, ranging from large and circular to telescopic and stalked. A large fluid-filled chamber containing ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
solution is used to aid buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
. Often the only organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
that is visible through the transparent tissues is a cigar-shaped digestive
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
gland
Gland
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...
, which is the cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
equivalent of a mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
. 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 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 squid represent no interest to commercial fisheries
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
.
Genera
- Subfamily CranchiinaeCranchiinaeCranchiinae is a subfamily containing four genera of glass squids.-Species:*Genus Cranchia**Cranchia scabra*Genus Drechselia ***Drechselia danae **Genus Leachia**Leachia cyclura**Leachia ellipsoptera...
- Genus Cranchia
- Genus Drechselia *
- Genus LeachiaLeachiaLeachia is a genus containing six species of glass squids. The genus is divided into two subgenera: Leachia and Pyrgopsis....
- Genus LiocranchiaLiocranchiaLiocranchia is a genus of glass squid.-External links:*...
- Subfamily TaoniinaeTaoniinaeTaoniinae is a subfamily containing eleven genera of glass squids.-Species:*Genus Bathothauma**Bathothauma lyromma*Genus Belonella**Belonella belone**Belonella borealis*Genus Egea**Egea inermis*Genus Galiteuthis...
- Genus Bathothauma
- Genus BelonellaBelonellaBelonella is a genus of glass squids....
- Genus EgeaEgea inermisEgea inermis is a species of glass squid in the monotypic genus Egea.-External links:*...
- Genus GaliteuthisGaliteuthisGaliteuthis is a genus of glass squids.-External links:*...
- Genus HelicocranchiaHelicocranchiaHelicocranchia is a genus of glass squids.-External links:*...
- Genus LiguriellaLiguriellaLiguriella is a genus of glass squids.-External links:*...
- Genus MegalocranchiaMegalocranchiaMegalocranchia is a genus of glass squids. It occurs circumglobally in tropical and subtropical waters.-External links:*...
- Genus Mesonychoteuthis
- Genus Sandalops
- Genus TaoniusTaoniusTaonius is a genus of glass squid. Although it comprises only two recognised species, it has been suggested there may be as many as five species.-External links:*...
- Genus TeuthoweniaTeuthoweniaTeuthowenia is a genus of three known glass squid. Species of this genus are characterized by their deep-sea habitat, clear bodies, and ability to engorge themselves with water to become larger when threatened. Each known species has a visible digestive gland, which serves a similar purpose as a...
The genus listed above with an asterisk (