Japetella diaphana


Japetella diaphana is a species of deep-sea pelagic octopus that inhabits the mesopelagic and bathypelagic zones of the ocean worldwide. It is known for its transparent body and bioluminescence.

Taxonomy

J. diaphana belongs to the subfamily Bolitaeninae and family Amphitretidae, within the order Octopoda and suborder Incirrata. Its class is Cephalopoda, in the subclass Coleoidea, and its phylum is Mollusca. This species does not have a set common name, but has been referred to as the "transparent octopus" or "gelatinous deep-sea octopus."

Anatomy and morphology

This species of octopus is characterized by its small, gelatinous body and distinctive bioluminescent capabilities, which play a role in counter-illumination and predator avoidance, communication, and predation. Its adaptations, including bioluminescent tissues and metabolic strategies, are well suited to the deep-sea environment, where visual predator-prey interactions are constrained by light availability.
Specimens collected from Hawaiian waters had a mantle length of 35–80 mm. Mature specimens obtained in the northeast Pacific and central and eastern Atlantic had a mantle length of 53–144 mm, a body mass of 18–235 g, and the number of growth increments in their beaks ranged from 21 to 207. Growth increments may take more than one day to form. It is suggested that its pace of life is slower and its lifespan is longer compared to neritic octopus species. This species also exhibits physiological traits and plasticity that allow it to survive hypoxic conditions. Unlike most ectotherms, J. diaphana is better able to tolerate hypoxic conditions at warmer temperatures.

Distribution and habitat

This octopus is found in tropical and subtropical oceans worldwide, including the Atlantic, Pacific, and Indian Oceans. Unlike many other octopuses, it is pelagic, inhabiting both the mesopelagic and bathypelagic zones. This species is the most widespread deep-sea cephalopod in the Mexican Pacific, having been sampled during the TALUD III-XVI-B research cruises in 11 stations off the west coast of Mexico. It has also been recorded in areas like the Gulf of California, Monterey Bay, the North Atlantic, and near the Cape Verde archipelago. In the Sargasso Sea, it is primarily found in the southern area, where its distribution is influenced by oceanographic features such as temperature gradients and water currents.
The octopus undergoes diel vertical migration, moving between depths in response to light availability. It is also known for its ontogenetic vertical migration, where juveniles start their life at shallower depths and gradually descend to deeper depths as they mature, with brooding females often found at depths exceeding.
J. diaphana is particularly abundant in regions with deep-water oxygen minimum zones, such as the one in the Eastern Tropical North Pacific off the coast of Mexico and Central America. It is well-adapted to the hypoxic conditions present in these zones. Despite its tolerance, this species avoids the most extreme hypoxic zones, instead populating the more oxygenated waters surrounding these areas.

Diet

The octopus is an opportunistic ambush predator, relying on its transparency to avoid detection and its bioluminescent characteristics to lure prey such as small crustaceans and zooplankton. Specimens collected off the west coast of Mexico contained crustacean remains in their stomachs, suggesting a diet composed mainly of copepods and amphipods. Japetella's ability to switch between prey types based on availability may be essential for its survival in resource scarce environments.

Reproduction

J. diaphana's reproductive strategy is characterized by synchronous ovulation, with mature females spawning approximately 2,000 eggs. A brooding female collected at in the Gulf of California carried 1,419 eggs in the pre-organogenetic stage, with a diameter of approximately 2.5 mm. Immature and maturing females have a higher number of oocytes, approximately 4,000, but many undergo resorption before reaching full maturity. This species broods its eggs within the arm crown, holding them in front of the mouth. This behavior likely restricts the ability to feed. It is estimated that embryonic development takes about 731 days in cold deep-sea conditions. It also had short, extended lobes that gave it a flower-like appearance. This organ originates from a muscular ring that undergoes cellular proliferation, followed by gradual degeneration of the muscle tissue. Its photocytes have a uniform cytoplasm with small mitochondria, granular aggregates, and microtubular or microfibrillar bundles. It may play a role in mate attraction, particularly in the low-light environments of the deep sea.

Threats

Japetella diaphana is a host for the protist parasite Hochbergia cf. moroteuthensis. Remotely operated vehicles in the Monterey Submarine Canyon observed that 7% of J. diaphana individuals carried this parasite.