AUSTRALIAN BIODIVERSITY RECORD - Calodema

Australian Biodiversity Record, 2007 (8): 1-124Pakistan, India, Sri Lanka, Thailand, Malaysia, Vietnam, China, Taiwan, and Japan. It rangesacross most of the Philippines and Indonesia, through to Australia and New Guinea to aboutas far east as the Coral Sea and New Caledonia.Habitat: Essentially lives on continental shelf habitats in water depths varying from around4m. to 55m and with a variety of substrate types. Occurs around coral reefs with sandybottoms in water depths as shallow as a few metres, up to around 25m. It is also an inhabitantof the turbid waters of river deltas, bays, estuaries and gulfs with muddy and/or sandybottoms. This species may be also found in the tidal stretches of tropical rivers, and can occurmany kilometres upstream from the sea, however it avoids freshwater conditions as suchwater can be fatal to its metabolism. Also known from the open sea, where it may occur inlarge numbers along current lines.Biology/Ecology: This is a relatively bulky, slow-swimming diurnal species that feeds on agreat variety of small fishes; it will also take small squid. As would be expected with a speciesoccurring across a wide geographic range, its reproductive conditions may vary dependingupon the location, but it would appear that development occurs during the Dry Season(winter), with births occurring during the Wet Season (summer). Mature females of Lapemishardwickii from the Persian Gulf and Asia appear to reproduce every year, with up to 7(usually about 2 to 4) young born in a brood. In Australia the brood size varies from 1 to 15(usually about 4 to 9). This would appear to be somewhat higher than brood sizes in Asianpopulations of Lapemis hardwickii. Similarly, larger females tend to produce more young in abrood in the Australian population, but brood-size and female size appears to be independentin some Asian populations of Lapemis hardwickii, but not in others. Despite its abundancevery little of this species’ habits in the wild is well understood. For instance it has beenobserved to gather in huge numbers along current lines on the open sea and such slicks ofsea snakes appear to extend for kilometres at times. Similarly, in a local context, smallgatherings of several individuals can be occasionally observed entwined together in a ball onthe surface of the sea - a puzzling behaviour that has also been observed in other species ofsea snakes as well. This species may also harbour small colonies of bryozoans, barnacles,small bivalves and hydrozoans attached to its skin, as well as a range of internal parasitictrematode and other unidentified worms associated with the skin and digestive system, soperhaps this balling behaviour is a response to the presence of attached bryozoans and thelike. Other Hydrophiids have been observed twisting themselves into knots, so as to scrapeoff organisms by abrading the body against itself as it crawls through such a knot; severalspecimens might collaborate in such behaviour as so form one of these sea snake balls.Toxicity: It may readily attempt to bite if harassed, so caution should be exerted whenhandling this species. Its venom has been the subject of considerable research and is knownto be highly toxic to humans. Urgent medical attention should always be sought in the eventof a bite from this species as there have been a number of human fatalities recorded from itsbite.Survival Status: Protected under the Qld Nature Conservation Act (1992), the Territory Parksand Wildlife Conservation Act (1998) and the WA Wildlife Conservation Act 1950 (asamended). Listed as a Marine Protected Species under the Australian EnvironmentalProtection and Biodiversity Conservation Act (1999). In Asia vast numbers are harvested forthe leather trade and this is undoubtedly having a serious impact on populations. Probably notunder threat overall at this stage as it is among the most abundant of all species of seasnakes, but its restricted distribution in Australian waters could potentially make it vulnerablein some parts of its range here given its rate of accidental capture in trawling operations.Etymology: The name ‘curtus’ is from the Latin, meaning ‘short’; the name 'hardwickii'honours the British naturalist General Hardwicke who collected the Type Specimen.Further Notes: There is some confusion about the taxonomic status of Lapemis hardwickii,with recent opinion favouring the submergence of this species with Lapemis curtus (Shaw,1802) due to the apparent unreliability of the fragmented vs unfragmented parietal conditionsthat have been traditionally used to separate these species (see references). Given that thedifferent ventral scale conditions, as well as numbers of mid-body scale rows vs number of55