Coelacanth  (Latimeria chalumnae)

The coelacanth is a ‘living fossil' previously believed to have gone extinct at the time of the dinosaurs until the first scientifically noted rediscovery in 1938 (3). This amazing specimen was dubbed the ‘most important zoological find of the century', and the species is a member of an ancient lineage that has been around for over 360 million years (4). Unlike any other living animal, coelacanths have a hinged joint in the skull, which allows the front part of the head to be lifted whilst feeding (4). They also have limb-like, lobed pectoral and pelvic fins and a unique tail consisting of three distinct lobes (5). Adding to the excitement surrounding the species is the ongoing controversy as to whether coelacanths or lungfish represent the closest living relatives to the first creature to walk on land (3). The scaly body is dark blue or brown in colour with white speckles, the pattern of which is unique to each individual and provides good camouflage against cave walls (3). A further unique feature is a receptor in the rostral organ of the head which can detect electric fields and may be used to locate prey or monitor its surroundings (5).

Fossil coelacanths have been found in all continents with the exception of Antarctica (6), but the distribution of this particular species is unclear. The first living specimen was discovered in 1938 off the coast of South Africa but until recently the only known population was located in the Comoro Islands, a small archipelago in the Mozambique Channel (3). Since then however, coelacanths have been observed off the northeast coast of South Africa in Sodwana Bay, as well as off Madagascar, Kenya and Tanzania (3). Individuals caught in Indonesian waters are currently considered a distinct species (Latimeria menadoensis) and are brown in colour.

Inhabits ocean waters ranging from 150 to 700 metres deep, where there are submarine caverns (2), deep reefs and volcanic slopes (3), but the coelacanth has also been tracked at depths of just 17 metres (9).

Due to the depth of their oceanic habitat, little is known about the natural ecology of this species. The young develop inside their mother (ovovivipary) and are attached to the outside of a yolk-filled egg of about 100 millimetres in diameter. The developing fish have this sac connected to their fore-belly region and as the yolk volume decreases and the embryo develops, the sac diminishes in size until it disappears completely. Shortly before birth the scar where the yolk was attached closes and heals completely (9). The mother then gives birth to as many as 26 live pups (3). These fish are very long-lived and some scientists believe them to live as long as 80 years (3).

They appear to be most active at night, spending the day hovering in submarine caves and foraging along the coast at night (3). Individuals observed in the wild appear to occasionally swim with their heads down in a ‘headstand' posture, but this is possibly a result of the light or electromagnetic field produced by the submarine (9). They are opportunistic drift-feeders, preying mainly on fish, including lantern and cardinal fish, eels, skates and many more (2).

Population numbers are particularly difficult to assess given the deep habitats of this species but the Comoros population was believed to show a dramatic decline in the 1990s (6). These fish are accidentally caught on lines whilst local fisherman search the deep waters for other species (6). Due to the likely slow reproduction rate and small number of offspring of coelacanths, the species is possibly particularly vulnerable to the removal of pregnant females from the population (6).

The coelacanth is protected from international trade by its listing on Appendix I of the Convention on International Trade in Endangered Species (CITES) (1). Fishermen of the Grand Comoro Island have also imposed a voluntary ban on fishing in areas where coelacanths (or ‘gombessa' as they are known locally) exist (5), in a vital effort to save their country's most unique fauna. The Coelacanth Rescue Mission is also distributing Deep Release Kits to local fishermen, which provide an effective method of returning accidentally caught fish to their deep habitat (3). There have recently been encouraging signs that the Comoros population is now stable (5), although careful monitoring will be needed to ensure this living fossil survives into the next millennium.

For more information on the coelacanth see:

• ‘Dinofish':
  www.dinofish.com/
• Weinberg, S. (2000). A Fish Caught in Time. HarperCollins Publishers, London.
• Walker, S.M. (2002). Fossil Fish Found Alive: Discovering the Coelacanth. Carolrhoda Books, Inc. Minneapolis.

Thank you to Robin Stobbs for adding to and authenticating this text (October 2004).