The West Indian Ocean coelacanth (Latimeria chalumnae) (sometimes known as gombessa, African coelacanth, or simply coelacanth) is a crossopterygian, one of two extant species of coelacanth, a rare order of vertebrates more closely related to lungfish and tetrapods than to the common ray-finned fishes. The other extant species is the Indonesian coelacanth (L. menadoensis).
The West Indian Ocean coelacanth was historically known by fishermen around the Comoro Islands (where it is known as gombessa), Madagascar, and Mozambique in the western Indian Ocean, but first scientifically recognised from a specimen collected in South Africa in 1938.
This coelacanth was once thought to be evolutionarily conservative, but discoveries have shown initial morphological diversity. It has a vivid blue pigment, and is the better known of the two extant species. The species has been assessed as critically endangered on the IUCN Red List.
Anatomy and physiology
The average weight of Latimeria chalumnae is 80 kg (176 lb), and they can reach up to 2 m (6.5 ft) in length. Adult females are slightly larger than males. Latimeria chalumnae exhibit a deep royal blue color with spots used as a camouflage tactic for hunting prey. Similar anatomical adaptations include the abundance of visual cells such as rods to help see when light is limited. This combined with the West Indian Ocean coelacanth's large eyes aid seeing in dark water.
Similar to cartilaginous fish, Latimeria chalumnae has a rectal gland, pituitary gland, pancreas, and spinal cord. To balance osmotic pressure, these fish adopt an efficient mechanism of osmoregulation by retaining urea in their blood.
Latimeria chalumnae are an ovoviviparous species, which means that they retain their eggs internally until they hatch. They also have low fecundity due to their long gestation period of around 12 months, though not much is known about their age of sexual maturity.
Habitat and behavior
L. chalumnae are usually found between of depth, but are sometimes found as deep as and as shallow as . L. chalumnae tend to reside in underwater caves, which are most common at these depths. This may limit their maximum depth range, along with lack of prey. They are known to spend the daytime within these lava caves, likely for protection from predators, and use the surrounding feeding grounds at night. Coelacanths are opportunistic in their feeding. Some of their known prey species are fish that include: Coranthus polyacanthus, Beryx splendens, Lucigadus ori and Brotula multibarbata. Their intracranial joint and associated basicranial muscle likely play an important but unresolved role in feeding.
Some individuals have been seen performing "headstands" as feeding behavior, allowing coelacanth to slurp prey from crevices within lava caves. This behavior is made possible due to the coelacanth's ability to move both its upper and lower jaw, which is a unique trait in extant vertebrates that have bone skeletons.
Population and conservation
L. chalumnae is widely but very sparsely distributed around the rim of the western Indian Ocean, from South Africa northward along the East African coast, especially the Tanga Region of Tanzania to Kenya, the Comoros, and Madagascar, seemingly occurring in small colonies. In 1991, it was estimated that 2-5 coelacanths were accidentally caught each year from Grand Comoro, making up about 1% of its population. Between 1991 and 1994, there was an estimated 30% total population reduction of the coelacanth. In 1998, the total population of the West Indian Ocean coelacanth was estimated to have been 500 or fewer, a number that would threaten the survival of the species. Near Grand Comoro, an island northwest of Madagascar, a maximum of 370 individuals reside. L. chalumnae is listed as critically endangered by IUCN. In accordance with the Convention on International Trade of Endangered Species treaty, the coelacanth was added to Appendix I (threatened with extinction) in 1989. The treaty forbids international trade for commercial purposes and regulates all trade, including sending specimens to museums, through a system of permits.