Diaphanous pelagic octopod

Japetella diaphana is a pelagic octopus of the order Octopoda and the family Amphitretidae ^[1]. It lives in deep water and, off Hawaii, made no daily vertical migration; there, females that were probably brooding were caught between 725 and 800 m depth ^[2].

Young animals have iridophores, cells that give iridescent reflections; gravid females, or those that have already spawned, lose nearly all of them and become heavily pigmented ^[2].

A maturing female develops a luminous ring around the mouth, which arises from a muscular ring whose cells multiply while the original muscle breaks down ^[3]. Mature specimens measured between 53 and 144 mm in mantle length ^[4].

Off the island of Oahu, Hawaii, opening-closing and open-net trawls caught 74 specimens, and no daily vertical migration was seen. Those under 20 mm mantle length were found mostly between 170 and 270 m and between 500 and 800 m ^[2].

Animals of 20 mm or more were caught between 725 and 1065 m, nearly 90% of them between 700 and 950 m, so individuals move deeper as they grow ^[2].

In the eastern tropical North Pacific the species is abundant outside the core of the oxygen minimum zone ^[5].

Two gravid females were caught at 1050 and 1065 m, and three spent females, probably brooding, between 725 and 800 m. In addition, newly hatched young turned up in the same catch as spent females and, in one case, the remnants of an egg string were still stuck to a sucker ^[2].

One brooding female, caught at 1352 m in the Gulf of California, carried 1419 eggs ^[4]. The increments counted in the upper beak ranged from 21 to 207; if they formed daily, the resulting ages would not fit the species' low metabolism and reproduction, so the authors conclude that it probably lives slowly and for a long time, and that age needs to be validated ^[4].

Young inferred that, off Hawaii, females move up to about 800 m just before or after spawning; this may shorten the trip of the hatchlings to their larval habitat near 200 m, and they probably go no higher because fishes become more numerous above 800 m ^[2].

Shipboard measurements on octopuses from the eastern tropical North Pacific showed a low metabolic rate, though higher than in octopuses from better-oxygenated waters, and a tolerance of oxygen shortage that was similar or greater ^[5].

Unlike most cold-blooded marine animals, its hypoxia tolerance depends on temperature in the opposite direction; even so it cannot meet its basal oxygen demand in the core of the oxygen minimum zone ^[5].

The IUCN Red List assesses the species globally in the Least Concern category (LC) ^[6].