AUSTRALIAN BIODIVERSITY RECORD - Calodema

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Australian Biodiversity Record, 2007 (8): 1-124imbricate, and numbering 226-286, each being only slightly wider than the adjacent bodyscales; ventrals in mature specimens (except on throat) form a distinct mid-line keel at thepoint of overlap of each ventral scale; tail strongly compressed vertically, paddle-like; preanalscales enlarged; ovoviviparous. Etymology: The name Astrotia is derived from ‘astrotos’(Greek) meaning ‘not covered’, and is believed to refer to the lack of broad ventral scales.Content: Astrotia stokesii (Gray, 1846).Astrotia stokesii (Gray, 1846)Hydrus stokesii Gray, J.E. (1846): Disc. Aust. Voy. Beagle…[p. 502, pl. 3]. Type data:holotype BMNH 1946.1.17.12. Type locality: Australian Seas.Hydrophis schizopholis Schmidt, P. (1846): Abh. Geb. Naturw. Hamburg 1: 164-172 [166, pl.15 figs 1-7]. Type data: holotype ZMH 387. Type locality: China Sea.Hydrus annulatus Gray, J.E. (1849). Cat. Spec. Snakes Coll. Brit. Mus., [p. 59]. Type data:holotype BMNH 1946.1.19.74. Type locality: Singapore.Hydrophis guntheri Theobald, W. (1868): Bull. Mus. R. Hist. Nat. Belg. 37: 67-74 [p. 69]. Typedata: presumed lost. Type locality: mouth of Hooghly River, India (as probably from theSandheads).Hydrophis granosa Anderson, J. (1871): Proc. Zool. Soc. Lond. 1871: 149-211 [p. 190]. Typedata: holotype IM. Type locality: mouth of Hooghly River, India (as Sand Heads).Hydrophis guttata Murray, J.A. (1887): J. Bombay Nat. Hist. Soc. 2: 32-35 [p. 33]. Type data:holotype BMNH 1946.1.19.73. Type locality: Makran coast, Iran and Pakistan (as MekranCoast).Description: Although there are longer species, this is usually a very large (if not the largest)species of sea snake, with a massive girth when mature, giving the body-form a very robustappearance. The head is usually not distinct from the thick neck, being long, deep, andsquarish (or weakly rounded) in shape when viewed from above, but with the snout slightly orsteeply angular in profile. There appears to be differences in head shape between the sexes,as well as some geographic variation. Overall the base body colour of mature specimens isusually creamish, yellowish-cream, pale brown or creamy-white, but occasionally muchdarker, more greyish to almost black specimens are found, with the head either creamishbrown,darker brown or black. In regards to dorsal pattern, specimens are sometimes withoutany pattern or with just an obscure reticulum of darker blotching along the lower lateral andventer. The largest (oldest?) specimens are often without any discernable pattern on auniform pale body. However, patterned specimens are the norm in any given population.There is usually a vertebral series of broad, dark leaden-grey or black transverse blotches,which are broadest along the mid-line and narrow to a point mid-laterally. Additionally, there isusually a smaller transverse blotch or group of blotches along the vertebral line between eachlarge blotch, and below this another smaller blotch on the upper lateral of the body. Thegeneral effect of this pattern is that of a series of broken transverse bands. In juveniles, thispattern is similar, but much more intense, with the base colour being almost white and thepattern being glossy black, with each large vertebral blotch in the shape of a sharply defineddiamond across the back, and so resulting in a prominent zig-zag pattern along the lateralzone. Occasionally, these dark blotches may coalesce along the vertebral and form a semicontinuousdarker dorsum. The smaller blotches between the larger markings are oftenrestricted to a single upper lateral spot or small blotch, but these markings are usually in aneat longitudinal alignment along the body. The ventral or lower body pattern usuallycomprises two series of small blotches in an alternating pattern, one along the mid-ventral lineand the other at the ventrolateral margin, but this pattern tends to be less distinct with age.Some significant features of this species' morphology are: head shields large andsymmetrical, with each shield much larger than adjacent nape scales; prefrontals present;nasals in contact; 1 preocular; 2 postoculars; 2 primary temporals; supralabials 10-11(occasionally divided); mental shield triangular in shape, wider than long, and a distinctmental groove; body scales relatively smooth, strongly imbricate, each with either a central24
Australian Biodiversity Record, 2007 (8): 1-124week keel or small line of tubercles, and in 46-63 rows at mid-body (with females having aslightly higher mid-body count than males); ventrals longitudinally divided, strongly imbricate,and numbering 226-286 (similar in males and females), each being only slightly wider thanthe adjacent body scales, and in mature specimens forming a distinct mid-line keel at thepoint of overlap of each ventral scale; preanal scales enlarged. It is said to attain a maximumtotal length of about 2 m., although 1.5 m. would be the usual maximum size - and femalestend to be somewhat larger than males, and have longer snout vent lengths. In Australianwaters a maximum snout-vent length of around 1.4 m. is achieved, with females being largerthan males which are seldom much over 1.2m. This is nevertheless an extremely largespecies, evidenced by an exceptional specimen 1.6 m. in total length that had a girth of 260mm. - making it probably the bulkiest of sea snakes. Variation in morphology suggests thatthis species may be composite.Distribution: Largely confined to tropical Australian seas, being found off the coasts ofQueensland, Northern Territory and Western Australia, and occasionally as far south as thewaters off Wollongong, New South Wales. Also widely known from the Arabian Gulf, acrossSouth East Asia, mainly from Pakistan, through Indonesia to New Guinea.Habitat: Mainly inhabits relatively shallow continental shelf areas near coral reefs with sandybottoms as well as around muddy river delta outflows and estuarine areas usually in watersfrom about 4m to 25m depth - but usually less than 10 metres.Biology/Ecology: This is both a diurnal and nocturnal species that feeds on a variety of smallfishes, with prey being actively hunted around coral. It may be often observed basking at thesurface in relatively turbid waters near rivers and is known to inhabit tidal waters somedistance up rivers as well. Specimens are occasionally found with growths of algae, barnaclesand bryozoans on its skin, and large infestations of nematodes may be carried in thestomach. It appears to have seasonal reproductive habits, but only limited data is presentlyavailable. Females carrying oviducal young have been found in mid-summer, and it ispresumed that the young are born in late Autumn. Litter sizes vary from 4 to 20, with anaverage of 10 to 14 being usual - juveniles are around 400 mm in length at birth.Toxicity: This is a potentially dangerous species as its venom is highly toxic to humans and itwill readily attempt to bite if handled or harassed. Caution should definitely be exerted withthis species, because on occasion it has been known to attack divers with little warning orprovocation. With its relatively large teeth and a large amount of venom, a wet-suit should notbe considered as adequate protection from penetration by the fangs of an adult snake.Similarly, specimens landed on trawlers vigorously bite anything within range, includingfishing gear, and those handled by researchers readily try to bite if restrained or handledroughly. If one is unfortunate enough to receive a bite from this powerful species, urgentmedical attention should be sought - even though to date there have been no known humanfatalities recorded against this species.Survival Status: Protected under the New South Wales National Parks and Wildlife Act (1974)but not listed in that State as a Threatened Species in any of the Schedules of the NSWThreatened Species Conservation Act (1995). Also protected under the Qld NatureConservation Act (1992), the Territory Parks and Wildlife Conservation Act (1998) and theWA Wildlife Conservation Act 1950 (as amended). Listed as a Marine Protected Speciesunder the Australian Environmental Protection and Biodiversity Conservation Act (1999).Probably not under threat, but its restricted distribution in Australian waters could potentiallymake it vulnerable in some parts of its range.Etymology: The name 'stokesii' honours English explorer and naturalist Admiral John LortStokes, who collected the species in 1840.25
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AUSTRALIAN BIODIVERSITY RECORD - Calodema

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