Histioteuthis eltaninae
From Wikipedia, the free encyclopedia
| Histioteuthis eltaninae | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Order: | Oegopsida |
| Family: | Histioteuthidae |
| Genus: | Histioteuthis |
| Species: | H. eltaninae |
| Binomial name | |
| Histioteuthis eltaninae Voss, 1969 | |
Histioteuthis eltaninae is a deep sea squid that is in the family Histioteuthidae. This family is also known as the cock eyed squids due to their asymmetrical eye shapes. Nancy A Voss was the one who made the discovery of this species in 1969.[1] It is commonly found in the Southern Ocean, mostly in the subantarctic and Antarctic regions. Its habitat can be found in deep pelagic zones like mesopelagic and bathypelagic zones.
The one feature that defines this family is their asymmetrical eye shapes. One large one facing upwards for predatory reasons and one small one facing downwards for protection against other predators.[2] Histioteuthis eltaninae also have photophores used for deep sea adaptations, such as camouflage and communication. They are known as predators among small fish and crustaceans, but easy food for bigger predators such as whales and seabirds. These squids play an important role in the Southern Ocean ecosystem because they are a mid trophic level species.
American biologist, Nancy A. Voss described Histioteuthis eltaninae in her monograph published in 1969. This described the Cephalopoda of the North Atlantic.[3] This deep-sea squid species belongs to the family Histioteuthidae, the cock-eyed squids. This nickname is given to them due to their two asymmetrical eyes.[1] This species is in a specific group within the genus called reversa group, which is a subgroup that helps recognize other related species by their body structures and photophore arrangements.[4]
Description (morphology)
Histioteuthis eltaninae is a small to medium sized squid with a typical mantle length that ranges approximately 66-88mm.[1] These creatures are typically soft-bodied with a gelatinous structure. This is an adaptation that most deep sea squid have.
What makes this species stand out is the presence of asymmetrical eyes. Every species of this particular family all have this unique feature.[1] One eye is significantly larger than the other. The eyes are oriented differently in their own way. The left eye is typically much larger than the right, but they both have useful functions for the squid.[2] The larger eye appears elongated and stretched out like a tube and has adapted for upward vision, whereas the smaller eye appears to have a more typical shape and has adapted for downward vision.
These types of squid have a specialized light producing organs called photophores or bioluminescent organs. This is common in deep sea environments where sunlight is very limited. Photophores are present on multiple parts of the body including the mantle, arms, and around the eyes. Each species has a specific pattern of photophores that can also be used for identification purposes.[1] Histioteuthis eltaninae have 3 rows of large photophores on the arms and 18 photophores around their eyes.[5] The more mature the species is, the number or pattern of photophores may change.
Histioteuthis eltaninae also have tentacles that include sucker arrangements on them. This arm structure is also used to help species identification. Histioteuthis eltaninae have 5 to 6 rows of suckers on each tentacle. The arms vary in length and may have different proportions. They also have gladius, which is a thin internal support structure commonly found is squid.[1]
Distribution and habitat
Histioteuthis eltaninae can be found in the Southern Ocean, mostly in subantarctic regions.[6] They typically live in deep pelagic environments. Their habitats are usually in the mesopelagic and bathypelagic zones where there is little to no sunlight in the water column.[2]
Their distributions across the Southern Ocean are believed to be influenced by ocean currents, temperature gradients, and oceanographic features.[7] All of these factors affect how they disperse during early life stages, as well as food source opportunities. The species has been observed and documented off the coast of New Zealand.[8]
Scientists have found that this species travels vertically threw the water column between 100m to below 1000m. Juveniles have been caught in open fishing nets around 200m during the day.[1]
Ecology and behavior
Histioteuthis eltaninae are very active predators that feed mostly on small fish and crustaceans.[9] Like most Antarctic squid, they are mid trophic level predators in marine food webs, meaning they are predators as well as prey to larger animals.[10] Just like other marine animals, their diets vary between juvenile and adult stages.
Most of the predators that eat this family of squid include sperm whales, sharks, seabirds, penguins, and seals.[1][11] This shows that these species of squid are very important to ecosystems within the Southern Ocean.
Antarctic squids' diets have been studied using a combination of things. The two main ways are gut content analysis and biochemical processes such as serological methods.[9] Pieces of cephalopod mantle and fins have been found inside the stomach contents. This makes researchers believe that Antarctic squid are hunting other cephalopods or competing with one another.[9] Other contents such as fish material such as eyes, vertebrae, and fin rays were also found in the digestive track.