AUSTRALIAN BIODIVERSITY RECORD - Calodema

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Australian Biodiversity Record, 2007 (8): 1-124Hydrophis elegans (Gray, 1842)Aturia elegans Gray, J.E. (1842). Monogr. Synop. Water Snakes [p. 61]. Type data: holotypeBMNH 1946.1.3.89. Type locality: Port Essington, NT.Distira grandis Boulenger, G.A. (1896). Cat. Snakes Brit. Mus [p. 293]. Type data: syntypesBMNH 1946.1.17.10-11, BMNH 70.11.30.71. Type locality: Malay Archipelago and QLD,QLD.Description: This is large species of Hydrophiid snake with a small head not distinct from theneck, and the anterior part of body much more slender than the posterior - which is robust,deep and highly compressed. The colouration is somewhat variable in this species. Adults arepale brown with only a faint pattern of darker blotches usually evident. Sometimes adults haveprominent dark banding that is more intense anteriorly, and often with secondary markingsbetween the main bands, and two alternating rows of dark spots along the flanks - one alongthe mid-lateral placing a dark spot below a pale interspace, and another along the lowerlateral of the body placing a spot below a dark transverse bar or blotch. The pale interspacesub-pattern comprises either rows of dark scales, spots or blotches within the paleinterspaces between the dark bands, and this is usually more obvious about the neck region,or along the posterior of the body and tail. However, juveniles and immatures are prominentlymarked with tan brown on the body, a black head and about 35-55 distinct black bands on thebody; these bands are broadest on the dorsum and venter, but somewhat narrow orincomplete on the flanks. The tip of the tail is greyish, and this is a paler grey than that of thedarker cross-bands - when bands are present. The ventral colour anteriorly is black, butbecoming paler posteriorly with alternating dark barring. Some significant features of thisspecies morphology are: head shields enlarged, symmetrical; anterior part of maxilla notarched upwards, and the tip of the fang projecting conspicuously below a line connecting thetips of the solid maxillaries; 6-7 maxillary teeth following fang; nasal separated from preocularby high 2nd supralabial; preocular single; postoculars 1-2 (mostly 2); one large primarytemporal; supralabials 6-7; usually only 3rd and 4th supralabial contacting orbit; mentalgroove present and distinct; mental triangular, broader than long, and not partially hidden inthe shallow mental groove; anterior chin scales large, and usually bordering mental groove;anterior part of body much more slender than the posterior, which is very deep and highlycompressed; dorsal body scales weakly imbricate, and slightly keeled or smooth; body scales25-30 rows at neck; mid-body scales in 35-49 rows; ventrals about 345-430 (females have ahigher ventral count than males); ventrals small and smooth and never foliform; posteriorventrals distinct, mostly undivided, and scarcely wider than adjacent body scales (exceptanteriorly, because ventrals here are often entire). Reaches a maximum total length of around2.2m, although a large specimen would be around 1.7 m. Females are sexually mature atabout 1.2m and tend to be noticeably larger than males.Distribution: This sea snake is known mainly from tropical and sub-tropical Australian seas,being found off the coasts of Queensland and the Northern Territory. It occurs commonly inWestern Australia, down to about Shark Bay or more rarely even as far south as GeographeBay in the extreme south-west. On occasions in summer, specimens occur off New SouthWales, Victoria and even Tasmania. Also known from the waters around southern NewGuinea.Habitat: Occurs in a variety of conditions, but more often found around deep water reefs (upto around 80 metres in depth). It has also been observed over soft muddy or sandy sedimentsin relatively shallow, turbid waters of river deltas, bays and gulfs on continental shelf areas(ranging from around 2m to 20m depths), and is known to enter tidal stretches of tropicalrivers several kilometres upstream from the sea.Biology/Ecology: Essentially a diurnal and fast swimming species that feeds on small squidand octopuses. It has also been reported to feed on a variety of small fishes - principally eels.Ovoviviparous, producing up to 33 (usually about 12) young in a brood during the late WetSeason to early Dry Season (March to May). The new-born young are around 400 to 500 mmin total length. It would seem that not all females are reproductive in any one year, implying38
Australian Biodiversity Record, 2007 (8): 1-124that individual females may not reproduce every year. On occasions, specimens are foundwith encrustations of barnacles, hydrozoans and bryozoans on the skin.Toxicity: This species rarely attempts to bite under normal circumstances, but caution shouldnevertheless be exerted, because when fishermen accidentally capture the species, it hasbeen observed to readily bite nets and other fishing gear. Studies have revealed that itsvenom is highly toxic to humans, so urgent medical attention should always be sought in theevent of a bite from this species - but there have been no recorded fatalities in Australia todate.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 Victorian Wildlife Act(1975) but not listed as threatened in the Victorian Flora and Fauna Guarantee Act (1988)],the Qld Nature Conservation Act (1992), the Territory Parks and Wildlife Conservation Act(1998), the Tasmanian National Parks and Wildlife Act (1970) and the WA WildlifeConservation Act 1950 (as amended). Listed as a Marine Protected Species under theAustralian Environmental Protection and Biodiversity Conservation Act (1999). Probably notunder threat, due to its great abundance but its scattered distribution in Australian waters andhigh frequency of accidental capture during trawling operations could potentially make itvulnerable in some parts of its range.Etymology: The name ‘elegans’ means elegant, and probably refers to the gracile body formof the species.Hydrophis mcdowelli Kharin, 1984Hydrophis macdowelli Kharin, V.E. (1983): Zool. Zh. 62(11): 1751-1753 [p.1751]. Type data:holotype ZIL 19678. Type locality: Northern Australian Shelf.Description: This is a medium-sized seasnake with a very small narrow head that is notdistinct from the neck, an extremely elongate forebody and a deep, strongly compressedposterior body. The base body colour is pale creamish dorsally, gradually becoming moreyellowish on the lower ventro-lateral and ventral surfaces. Adults possess a series of blackishdorsal blotches on the dorsum, with each blotch terminating about the upper to mid-lateral ofthe body. In some specimens the pale interspaces can possess a blackish narrow line orseries of broken bars or spots as well. There are three separate longitudinal rows of darkermarkings along the flanks as follows: an upper lateral line of dark greyish inverted triangle orelongate rhomboid-shaped markings with each below a pale interspace; a reduced series ofirregular blotches along the lower lateral zone, with each blotch being positioned below a darkdorsal blotch; a third series of tiny blackish or greyish spots or bars, each below a paleinterspace. The tail is usually prominently marked with 4 or 5 wide but faint greyish or blackishtransverse bands, with a narrow blackish line within each pale interspace. The dorsum of thehead is dark olive or black, and the throat and anterior venter is black fading to dark grey, withthe rest of the ventrals yellowish. Some significant features of this species’ morphology are:Head shields enlarged and symmetrical; 5-6 maxillary teeth following fang; preocular 1;postoculars 2; supralabials 7, with 3rd and 4th contacting orbit; primary temporals 1; bodyscales smooth, imbricate but keeled on neck; 23-26 body scale rows on neck; mid-bodyscales in 35-42 rows; ventrals smooth, about 243-274 and mostly entire, and wider thanadjacent body scales; Usually attains a maximum total length of only around 80 cm., althoughit can reach a total length of nearly 1.2m.Distribution: Known only from tropical Australian seas, off the coasts of Queensland, NorthernTerritory and Western Australia to about as far south as the Pilbara coast. Also known from asmall part of the southern coast of New Guinea, and across to New Caledonia.Habitat: More often found in shallow (about 7-25 metres deep) waters over flat open sandybottoms of bays and gulfs, but also known from turbid conditions of estuaries and river deltas,but also rarely in deeper waters on continental shelf areas.39
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AUSTRALIAN BIODIVERSITY RECORD - Calodema

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