Friday, February 10, 2012

The Pygmy Seahorse

        The pygmy seahorse is one of the smallest seahorses of the world measuring just 2 cm in height and is undoubtedly one of the most well camouflaged species in the oceans, being extremely difficult to spot among the gorgonian coral it inhabits. So effective is this camouflage that the species wasn’t actually discovered until its host gorgonian was being examined in a lab. Large, bulbous tubercles cover this species’ body and match the colour and shape of the polyps of its host species of gorgonian coral, while its body matches the gorgonian stem. Two colour morphs exist: pale grey or purple individuals scattered with pink or red tubercles are found on the similarly coloured gorgonian coral Muricella plectana, and yellow individuals with orange tubercles are found on gorgonian coral Muricella paraplectana. It is not known whether individuals can change colour if they change hosts, although the ability to change colour according to their surroundings does exist in some other seahorse species.

Range: The pygmy seahorse is known from coral reefs in the tropical western Pacific around Australia (Queensland), Indonesia, Japan, New Caledonia, Papua New Guinea and the Philippines.

Status: The pygmy seahorse is classified as Data Deficient (DD) on the IUCN Red List, and listed on Appendix II of CITES.

Biology: Only known to occur on gorgonian corals of the genus Muricella, the pygmy seahorse is typically found between 16 and 40 metres depth. Adults are usually found in pairs or clusters of pairs, with up to 28 pygmy seahorses recorded on a single gorgonian, and may be monogamous (Each male will have only one female). Unusually, it is the male, and not the female, that becomes pregnant in seahorses. Pygmy seahorses are unique from larger seahorses in other ways. There is no pouch at the base of the tail. The male still incubated the eggs, but he does this in a brooding cavity in the trunk (body) region with a downward facing opening. This is likely an adaptation due to their small size.

Breeding occurs year-round, and gestation averages two weeks, during which the male carries the eggs concealed within his trunk region. In one birth witnessed underwater a male ‘gave birth’ to a brood of 34 live young. The young look like miniature adult seahorses, are independent from birth, and receive no further parental care.

Threat: Very little is known about the total number of pygmy seahorses, population trends, distribution, or major threats. It has therefore been classified as Data Deficient on the IUCN Red List. Because of the unusual and attractive colouration of this small seahorse it is possible that it could be being collected for the aquaria trade, although no international trade in the species has been recorded.

Conservation: All seahorses are listed on Appendix II of CITES, effective as of May 2004, limiting and regulating their international trade. Australian populations of pygmy seahorses are listed under the Australian Wildlife Protection Act, so that export permits are now required, although they are only granted for approved management plans or captive-bred animals. With such limited data available on this fascinating animal, there is an urgent need for further research to be conducted on its biology, ecology, habitat, abundance and distribution, before its status can be properly assessed and conservation measures implemented accordingly. The remarkably effective camouflage of this astonishing species may make such surveys particularly challenging, but hopefully it will also help protect it from exploitation, keeping it safe and hidden in the Pacific reefs where it belongs.


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