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Wells, R. W. (2002). Forts. taxonomic notes on some australian freshwater turtles of the genera chelodina and elseya (reptilia: chelidae). Australian Biodiversity Record, 2, 1–30.
Added by: Admin (14 Aug 2008 20:36:28 UTC) Last edited by: Beate Pfau (10 Jan 2009 15:34:26 UTC) |
| Resource type: Journal Article BibTeX citation key: Wells2002a View all bibliographic details  |
Categories: General Keywords: Australien = Australia, Chelidae, Chelodina, Chelodina longicollis, Chelodina novaeguineae, Elseya, Elseya novaeguineae, Elseya stirlingi, Habitat = habitat, Schildkröten = turtles + tortoises, Systematik = taxonomy Creators: Wells Collection: Australian Biodiversity Record |
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| Abstract |
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Chelodina Elseya The Chelid turtles of Australia are still far from being a taxonomically stable group, despite expanding interest in all aspects of their biology by herpetologists during the past 15 years or so. The two genera that are the subject of this paper contain a number of species that are in urgent need of taxonomic revision. I provide below my thoughts on only a small part of the freshwater turtle fauna of Australia, and intend commenting on several other species in a future article. I would like to thank John Cann - undoubtedly the leading authority of our Chelid turtles - for his advice and encouragement to publish my thoughts. Eastern Long-necked Turtle Chelodina longicollis (Shaw, 1794) This is probably Australia’s most well-known freshwater turtle and yet it has almost been totally ignored from a taxonomic perspective. Despite having been first described over 200 years ago no one has yet published a definitive study which systematically examines the morphological variation present across this species’ range. Such a study is obviously beyond my meagre resources, so I provide below what is essentially an artificial or composite diagnosis that is intended merely as an introduction to the ‘species’. I believe however, that Chelodina longicollis at the very least represents a polytypic species, with each of the major drainage basins having their own distinct subspecies. But there is the slight problem that one of these populations may have been named in the past (Chelodina sulcifera Gray 1855) and unfortunately its Type Locality was only specified as ‘Australia’. As to the application of this previous synonymy, well I think that all past names that cannot be unambiguously applied to species should be regarded as nomen oblitum (as is permitted by the Code) and the taxa formally allocated a new name. It has been suggested by Cann (1998) that the name for the inland population should be Chelodina sulcifera Gray, 1855 and from my observations the variation in morphology displayed by this species across its range does indeed suggest that it is composite and that Chelodina sulcifera should be resurrected from the synonymy of Chelodina longicollis for one of these populations. But which one? Diagnosis: It is a medium-sized to large Chelid turtle with a deep body-form, somewhat rounded carapace and only 4 claws on each forelimb. The head is small, moderately depressed, with a blunt rounded snout and the eyes tend to be laterally directed are bright and expressive with a white or yellowish iris ring and a small black pupil. As its common name suggests, the neck is quite long being about two thirds the carapace length, and the skin of the dorsal and lateral part (i.e. more exposed) is covered with small low, rounded or pointed tubercles. Differences between the sexes are minimal, but the carapace of adult females tends to be more convex posteriorly than that of the male, but in both the tail is quite small, and only slightly larger in the males. In mature specimens the colouration varies somewhat depending upon location. The carapace may be tan to dark brown to even black and be with or without brownish or blackish edges to the plates; some specimens may have scattered darker blotches or splotches of various size over the carapace as well. Generally aged or larger specimens are darker, and many individuals may have their carapace colour obscured by a dense covering of green algae. The ventral surface of adults may be yellowish, creamish or whitish, with the sutures of the plastral plates edged in black to a varying extent, and sometimes there may be a reddish or russet tinge to the plastron as well, but in others the plastron may be almost black, with only minimal paler colouration. It should be noted also that water quality or substrate condition may also affect plastral and/or carapace colouration. Generally, the skin colour is very dark grey dorsally, but whitish or pale greyish to creamish-yellow ventrally. In hatchlings the colouration and pattern is usually spectacular, with the carapace black, and the plastron bright red or orange with extensive black edging extending well beyond the plastral sutures. As the turtles age (by about 1-2 years after hatching) the carapace may become more brownish and the plastral colour becomes more creamish and the sutures progressively more narrowly edged with black. Some other significant features of this species' morphology are: gular shields in contact in front of the intergular; inguinal musk glands present; plastron greatly expanded anteriorly, being widest about the position of the humerals; plastron one and half times as long as broad, and with the anterior lobes of the rounded and extending laterally beyond the inner edges of the marginals; intergular at least twice, or more than twice the length of the pectoral suture; posterior boundary of anal shields forms a 'V'-shape. Generally, the carapace is strongly convex, has a slight to deep vertebral groove and is usually smooth to somewhat rough in surface pattern. The carapace is broad and more or less oval-shaped with some posterior expansion (particularly in those from the inland or Murray-Darling River System population). The edges of the carapace may be slightly upturned with age, but there can be notable variation in shell shape from one area to another as well as within a population due to ontogenetic changes. There are also apparent size differences within Chelodina longicollis, with eastern drainage populations reaching a much smaller maximum carapace length (about 250 mm.) than those from the Murray-Darling River System (around 350 mm). As herein defined, this is a species found under a very wide range of environmental conditions. It is found across a vast area of eastern and south-eastern Australia, having been found throughout south-eastern Queensland, eastern, central and most of western New South Wales, all but the driest and coldest areas of Victoria, and large areas of south-eastern South Australia. This species lives in most freshwater habitats, ranging from ephemeral ponds to large rivers. However, the most favoured habitats utilised by this species are usually slow-flowing or still waters, such as found in small creeks, ponds, swamps, marshes, billabongs and of course man-made waterbodies such as farm dams and bore drains. Under unnatural conditions - such as water storage dams and distribution channels - very large populations may be found. Favoured sites usually have good water plant growth with exposed logs or rocks for basking. The reproduction biology of this species is fairly well known. It produces up to 24 eggs in a clutch (although about 12 is usual), the eggs being laid in a small hole in the earth a few metres above and several metres away from the water - although in flood-prone areas nesting sites may be many metres away from the water's edge. Nesting takes about three hours with females usually depositing the eggs during the daylight under humid and cloudy conditions, with nests often constructed in very hard soil. When nesting under hard soil conditions, the female excretes a large quantity of water from its cloaca to soften the soil and make the whole process easier. Sometimes a female will also construct other nesting cavities nearby to the actual nest, but not actually use them for laying, the process apparently being an anti-predator device to hide the true position of its eggs. The period of incubation varies depending upon the site and prevailing climatic conditions. The young emerge after around 120 to 150 days incubation, although some may hatch earlier (around 90 days) or later (the record is 185 days). Mating usually takes place in Autumn (April-May), with laying taking place in Spring to early Summer (September-December). During the breeding season, females may be recognised by scratching injuries to the head and neck which are received from males during mating, but males of this species will engage in prolonged territorial fights between themselves that can result in much more severe bites to the head, neck and limbs. The Eastern Long-necked Turtle consumes a range of aquatic invertebrates, small fish and carrion. It is fully 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 NSW Threatened Species Conservation Act (1995). It is also protected under the ACT Nature Conservation Act (1980), the Victorian Wildlife Act (1975) , the SA National Parks and Wildlife Act (1972) and the Qld Nature Conservation Act (1992). It is not only generally regarded as common throughout its range, it is widely considered to be one of the most adaptable and successful Australian reptiles, persisting even in seriously degraded wetland environments. Although this species is mainly aquatic in habits, they may also periodically travel overland some distances from water. Often it may be found crossing roads mainly during Spring or Summer, their overland activity usually corresponding with their reproductive season, and initiated by a sudden drop in atmospheric pressure associated with periods of heavy rainfall. During these overland sojourns many may be killed by traffic or taken by predators. In the hotter Summer weather, when even quite large water-bodies begin to dry up, Long-neck Turtles may bury themselves in the mud under the protection of overhanging banks, or will leave the drying pond or creek entirely and aestivate on land by burying themselves beneath several centimetres of soil and litter under patches of low vegetation until the late Summer or Autumn rains allow the recolonising of waterbodies. In the late Autumn months Chelodina longicollis usually becomes much less active, and if the weather turns too cold, it enters a period of dormancy for several weeks. During this period, the turtles will bury themselves underwater beneath the litter or logs on the bottom of streams or ponds, where they enter a state of hibernation-like inactivity over Winter until the warmer weather returns. Apparently the turtles extract their oxygen requirements from the water during their sleep, but the precise mechanism by which they do this has not been studied anywhere near sufficiently, although the phenomena has been known for over a century. Under captive conditions, turtles will also leave the water for the winter months and hibernate beneath litter and shallow soil on the land, but this is usually because the bottom of their pond lacks a suitable substrate for underwater hibernation. Another interesting aspect of this species' ecology concerns its use of an apparent chemical deterrence against potential predators. This species can voluntarily emit a strong, foul-smelling odour when disturbed or agitated. The smell, which can only be described as strongly pungent, comes from a viscous exudate secreted from glands around the bridge of the shell and this odour is also apparent in hatchlings as well, but not anything quite so strong as in the adults. This is a hardy species that is known to have a very long lifespan, with a record specimen living to nearly 60 years of age. New Guinea Long-necked Turtle Chelodina 'novaeguineae' Boulenger, 1888 The readily observed variation in morphology suggests that the Australian populations currently referred to this species are not 'novaeguineae' at all, but instead represent two undescribed species, one in the eastern flowing rivers of north-eastern Queensland, and the other in the drainages of the Gulf of Carpentaria in Qld across to the eastern Northern Territory. They have been included here under the name 'novaeguineae' only for convenience. However, Wells and Wellington (1985) expressed the view that Chelodina novaeguineae did not occur in Australia, and accordingly applied the name 'Chelodina rankini' to the eastern population but this was initially regarded by the herpetological community as a merely a synonym of Chelodina novaeguineae. In recent times however, some have begun to accept that the Australian populations are not referable to novaeguineae, but the name 'Chelodina rankini' has been regarded as a nomen nudum and therefore unavailable due to the brevity of the original decryption. This is arguable however as the description, despite its brevity, does conform to the requirements for availability under the Articles of the Code of Zoological Nomenclature. I could have merely redescribed Chelodina rankini in this paper and in so doing make the name unambiguously available under the Code, but I have chosen to defer formally redescribing Chelodina rankini following a request from Mr Scott Thomson in 2000 who stated that a paper on the Chelodina novaeguineae-complex was in press at that time. I am not aware of such a paper having as yet appeared and I still await its arrival with interest. Therefore the following diagnosis must be regarded as somewhat artificial as it includes the New Guinea population. Diagnosis: This is a small to medium-sized Chelid turtle with a long neck, moderately deep body-form and with only 4 claws on each forelimb. The head is moderately depressed, and the snout is blunt in the Australian populations (i.e. not protruding or beak-like as in Chelodina novaeguineae from New Guinea) and the eyes tend to be laterally directed. In mature specimens the colouration varies somewhat depending upon location. The carapace may be brown to black and with or without brownish or blackish speckling. The ventral surface may be creamish or whitish, with the sutures of the plastral plates edged in black to a varying extent. In juvenile colouration and pattern there are notable differences between the Australian and New Guinea populations. Juveniles of the Gulf drainage population of Australia (Roper River, NT) have a black carapace with paler spotting along the edges, a bright red and black-mottled plastron, and are distinctively bright red on the inside of limbs, as well as on the edges of the jaw and under throat. Juveniles from the eastern drainages (Chelodina rankini) have a yellowish plastron with black mottling, and a more dark greyish carapace. Some other significant features of this species' morphology are: gular shields in contact in front of the intergular; inguinal musk glands present; plastron greatly expanded anteriorly, with the anterior lobes of the plastron rounded and not extending laterally any further than the inner edges of the marginals; intergular at least twice, or more than twice the length of the pectoral suture. Generally, the carapace is strongly convex, has a distinct vertebral groove and is more 'crinkled' or irregularly sculptured in surface pattern with Australian populations - as opposed to the distinctive radiating lines of topotypic Chelodina novaeguineae. The carapace is oval-shaped with some posterior expansion, but there is notable variation in shell shape from one area to another. The carapace shape is more rounded in the Gulf drainage population, but somewhat ovate in shape with the rear marginals flaring outwards in the eastern (Chelodina rankini) population. The neck of the eastern population (Chelodina rankini) has numerous flat wart-like protuberances, whereas in the Gulf drainage (e.g. Roper River, NT ) population these warty structures are interspersed with larger conical tubercles. There are also apparent size differences within the Australian Chelodina novaeguineae, with eastern drainage population reaches a maximum carapace length of about 260 mm., but those from the Gulf drainage being much smaller at a maximum size of around 200 mm. As herein defined, the Australian members of ‘novaeguineae’ are species of tropical north-eastern and northern Australia, having been found at scattered locations throughout coastal north-eastern Queensland, and in most of the drainages entering the Gulf of Carpentaria from western Cape York Peninsula, westwards to the Roper River system in the north-eastern Northern Territory. An apparently isolated inland population occurs near Lake Woods, near Daly Waters NT as well and I have personally examined a living specimen of this population. It also lives in the larger water bodies such as the Roper River, and the MacArthur River NT, as well as the Albert River, Mitchell River, Gilbert River, Edward River and Burdekin River in Qld. This is mainly a species of shallow slow-moving or still water-bodies such as inland or coastal swamps, marshes, billabongs or lagoons. It also inhabits the seasonally dry river headwaters. During the Dry Season this species is known to aestivate in the mud or under exposed overhanging banks as watercourses dry to chains of ponds or disappear entirely. Specimens will also move overland to refuges provided by larger water bodies as their lagoon or pond habitats dry up. Similarly, as flooding occurs during the Wet Season, overland migration will occur as well. Up to 16 elongate brittle-shelled eggs are layed in a clutch about August and these usually hatch after around 120 days incubation. This is a carnivorous species, consuming a range of aquatic invertebrates such as small crustaceans, small fish and carrion. It is protected under the Qld Nature Conservation Act (1992) and the Territory Parks and Wildlife Conservation Act (1998). Regarded as common in most parts of its Australian range.
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