Bolitaeninae: Difference between revisions

The '''Bolitaenidae''' isare a family of small, common [[pelagic zone|pelagic]] [[octopus]]es found in all tropical and temperate oceans of the world. The family's [[taxonomy]] is not entirely certain; recent research suggests there should be just two genera, ''[[Bolitaena]]'' and ''[[Japetella]]'', both of which are thought to be monotypic. Under this view, the family would represent two very similar species: ''[[Bolitaena pygmaea]]'' and ''[[Japetella diaphana]]''.

Bolitaenids are characterised by their small size—up to 8.5 centimetrescm or 3.3 inchesin [[mantle (mollusc)|mantle]] length and 12 centimetrescm total length in ''Japetella'' species—andspecies, and their comparatively short arms, much shorter than their dome-shaped mantles. The arms have a single series of suckers; in males, these suckers are greatly enlarged on the third right arm. In ''Bolitaena'' (but not ''Japetella'') this arm is also modified into a [[hectocotylus]], an appendage used to facilitate transfer of [[spermatophore]]s during mating.

Perhaps the most striking feature of the family is seen in mature females; upon maturity, a ring-shaped [[photophore]]—a light-producing organ—develops to encircle the mouth. This is believed to be an adaptation to life in gloomy, deep ocean waters; the [[bioluminescence|bioluminescent]] ring may help males and females to find each other.

Mature bolitaenids occupy depths in the [[mesopelagic|meso]]- to [[bathypelagic]] zones of the water column, down to about 1,425 metresm. Younger animals (under 20 millimetresmm mantle length) are known to remain in shallower waters, either from 170-270 metresm or 500-800 metresm, depending on size. ''Japetella'' is known to venture into far northern waters.

Mating is thought to occur at or below 1,000 metresm depth. In the darkness, whether mating is successful or not may depend on the female; she can choose whether to signal the male with her circumoral photophore. The light emitted by the photophore is believed to be of a specific wavelength, possibly both preventing miscommunication and the attraction of predators.

| footer = Immature bolitaenids at various stages of development: ('''left''') immature specimens of ''J. diaphana'' from [[Sumatra]] (top left), southwestern [[Sri Lanka]] (top right), and southern [[Sierra Leone]] (bottom); ('''centre left''') immature ''J. diaphana'' from the [[Gulf of Guinea]]; ('''centre right''' and '''right''') juvenile female ''B. pygmaea''.

After mating, the female then rises to about 800 metresm to brood. Her eggs are interconnected by a number of stalks; the whole mass is held safely by means of suckers near her mouth. Due to the cold (4–5°C) environment, brooding likely takes several months; the female is thought to forgo food during this entire period. After hatching, the young octopuses rise to the productive, upper 300 metresm of the [[water column]], where they remain until reaching a certain size (7–20 millimetresmm). As they mature, the young begin their gradual descent to the [[mesopelagic]] and eventually [[bathypelagic]] zones.

[[File:Bolitaena pygmaea2.jpg|thumb|Male ''B. pygmaea'', probably taken during the Michael-Sars Expeditionexpedition]]

**''[[BolitaenaB. pygmaea]]''

**''[[JapetellaJ. diaphana]]''