The coelacanth is a deep-sea fish, often referred to as a “living fossil” because its body plan has remained largely unchanged for millions of years. This ancient lineage of lobe-finned fish appeared in the fossil record over 400 million years ago and was thought to be extinct until a specimen was caught in 1938 off the coast of South Africa. Today, only two living species in the genus Latimeria are known: the West Indian Ocean coelacanth (Latimeria chalumnae) and the Indonesian coelacanth (Latimeria menadoensis). The Indonesian species, known locally as raja laut or “king of the sea,” represents a geographically distinct population in the Western Pacific.
The Second Coelacanth Discovery
The identification of a second living coelacanth species began with an unexpected sighting in the Indonesian archipelago, approximately 10,000 kilometers from the established African population. The discovery occurred in September 1997 when American marine biologist Mark V. Erdmann and his wife, Arnaz Mehta, encountered a large, unusual fish at a fish market near Manado, North Sulawesi. They recognized the specimen as a coelacanth, but its distinct brownish-gray coloration, rather than the African species’ deep blue, suggested it might be a different species.
Erdmann photographed the fish before it was sold, and the photographic evidence confirmed the existence of a coelacanth population in the region. A second specimen was caught by local fishermen in July 1998 off Manado Tua Island. This fish allowed for detailed scientific analysis, including morphological study and genetic sequencing. Researchers published their findings in 1999, confirming the Indonesian fish as a new species, Latimeria menadoensis, based primarily on genetic divergence and color.
Distinguishing Characteristics
The most apparent difference between the two coelacanth species is their coloration. The African coelacanth (L. chalumnae) exhibits a deep, cobalt blue body color, often adorned with white flecks. In contrast, the Indonesian coelacanth (L. menadoensis) presents a brownish-gray background coloration, though it also features a pattern of white speckles across its body and fins.
While adult coelacanths share many similar external features, genetic evidence provided the clearest distinction between the two populations. Analysis of mitochondrial DNA revealed a divergence of approximately 4.1% between the Indonesian and African specimens, indicating significant separation. This genetic gap suggests the two species have been separated for a substantial period, estimated to be between 30 and 40 million years. Minor morphological differences have also been noted, such as the Indonesian species having comparatively longer pectoral fins and shorter pelvic fins.
Deep-Sea Habitat and Behavior
The Indonesian coelacanth inhabits the deep, cold waters of the Western Central Pacific, with most sightings concentrated around the waters of North Sulawesi, including Manado Bay, Talise Island, and Gangga Island. Its habitat is characterized by steep, rocky slopes and volcanic terrain, which provide shelter in the deep ocean. The species is typically found at depths ranging between 150 and 200 meters, though observations have extended its vertical distribution to 700 meters.
These coelacanths seek out deep carbonate caves, grottos, and narrow overhangs, which they use as resting places during the day. The water temperature in these preferred daytime habitats ranges from 14°C to 20°C. Observations show that the fish leave these caves late each afternoon to forage along the coastal slopes at night. As opportunistic predators, they consume deep-water prey such as cuttlefish, snipe eels, and other small fish, possibly using their rostral organ, an electroreceptive device in the snout, to locate prey.
Conservation Status and Monitoring
The Indonesian coelacanth is classified as Vulnerable (VU) on the IUCN Red List of Threatened Species, compared to the Critically Endangered African species. The primary threat to this population is accidental capture, or bycatch, by local deep-sea fishermen using specialized gear. Its deep-water existence makes direct population monitoring difficult, which limits the data available for conservation efforts.
The discovery of L. menadoensis quickly led to its protection under Indonesian National Law, with trade banned under CITES Appendix I. Conservation efforts have focused on community awareness, particularly around the Bunaken National Marine Park, to encourage local fishermen to report sightings and accidental catches. The species has become a flagship for marine conservation in the region, helping ensure the long-term survival of this ancient fish.