AUSTRALIAN BIODIVERSITY RECORD - Calodema

Australian Biodiversity Record, 2007 (8): 1-124series of 40-60 whitish 'bands' on a blackish body; the head and neck is black. These bandsare most distinct and complete on the posterior, deeper part of the body, but are reduced to aseries of large oval spots on the lateral part of the very slender anterior body. As specimensage, the pattern becomes far less distinct. Some significant features of this species'morphology are: head shields enlarged, symmetrical; nasal separated from preocular by high2nd supralabial; 3rd and 4th supralabials suborbital; 5-6 maxillary teeth follow fang; 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;neck scales in 17-21 rows; body scales in 29-37 rows at mid-body, with females tending tohave slightly higher mid-body counts than males; body scales juxtaposed and those of thelower lateral being larger than dorsals, and either possessing prominent tubercles or largekeels, which are most prominent in males; small ventrals, about as wide as, or only slightlywider than adjacent body scales and never foliform; posterior ventrals indistinct, but alldivided by a longitudinal fissure; ventrals about 220-290 (females have a higher ventral countthan males). Variation in morphology suggests that this species may be at the very leastpolytypic. Attains a maximum total length of around 1m., with a snout-vent length of onlyaround 70-90 cm. Females grow larger than males, and are sexually mature at around 70cm.At birth this species is relatively large, at 330 mm to 380 mm in total length.Distribution: This is a widely distributed species, being found from the Persian Gulf,throughout South East Asia, across Indonesia to Australasia and well into the Coral Sea,although it does not reach New Caledonia. However, in Australian waters, this species hasonly been recorded (uncommonly) from the Torres Strait of Queensland. It is also knownrarely from the southern Great Barrier Reef part of south-east Queensland - probably asvagrants.Habitat: Although largely restricted to coral reefs in relatively shallow continental shelf watersover sandy substrates to a depth of around 30m, occasionally specimens are found inmangrove estuaries.Biology/Ecology: A fast-swimming, diurnal species that feeds on a variety of small fishes -mainly eels, which it presumably hunts by burrowing into sandy substrates. This is aovoviviparous species, that produces from 1 to 6 (average 3) young in a brood. There isconsiderable variation in the timing of reproduction across this species’ range, but it wouldappear that females are gravid during Spring and give birth in Summer. For example, in thePersian Gulf, they are gravid in Spring. In various parts of Asia, gravid females may occur inboth the inter-monsoonal period (April) as well as just after the end the summer monsoonseason (June-July). A gravid female has also been found in Australia during the early WetSeason (December).Toxicity: This snake rarely attempts to bite under normal circumstances, but caution shouldnevertheless be exerted, because its venom is highly toxic to humans. Urgent medicalattention should always be sought in the event of a bite from this species.Survival Status: Protected under the Qld Nature Conservation Act (1992). Listed as a MarineProtected Species under the Australian Environmental Protection and BiodiversityConservation Act (1999). Probably not under threat, but its restricted distribution in Australianwaters could potentially make it vulnerable in some parts of its range.Etymology: The name 'gracilis' means 'slender', and refers to the body-form of the species.Genus Polyodontognathus Wall, 1921Polyodontognathus Wall, F. (1921). Ophidia Taprobanica or the Snakes of Ceylon. [p. 374].Type species: Hydrus caerulescens Shaw, 1802 by monotypy.Diagnosis: A monotypic genus of Hydrophiid snakes readily identified by the followingcombination of characters: Head shields enlarged, symmetrical; 12 or more solid maxillaryteeth following fang; dentary teeth 22 or more; heart about midway along body; valvularnostrils and lingual fossa; nasal separated from preocular by high 2nd supralabial; 3rd and 4th47