Post by Ceratodromeus on Aug 31, 2016 3:34:42 GMT 5
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Subclass: Anapsida
Order: Testudines
Suborder: Cryptodira
Superfamily: Trionycoidea
Family: Trionynichidae
Subfamily: Trionynichinae
Genus: Nilssonia
Species: N.gangetica
Conservation status
This species of freshwater softsell is considered Vulnerable throughout their geographic distribution; In fact they are legally protected in some parts of their range, namely India. However this does not negate the fact that there is a demand for the flesh of the indian softshell turtle(turtles in general), for consumption, or medicinal purposes. In the latter case they are exported to China, but are also used in Indian medicinal practices{1,3}. In India the species is at risk especially in urban areas, where pollutants fill the waters and put the turtles at risk of E.coli infections. In the span of a single year(2010-2011), at least two dozen of these turtles were found deceased, and while the cause of death had not been concretely determined, the thing the deceased turtles had in common was the contamination of the E.coli bacteria{2}.
Description
Softshell turtles are animals characterized by their flattened shell profile as opposed to the more dome shaped seen in other aquatic turtle species, as well as the pig-like snout and small eyes. The Indian softshell Possess drab colorations, the head being a contrasting light green with black striping on the dorsal side of the head, intersecting the eye and running to approximately the nape of the neck. Juveniles are more brightly colored and marked, possessing severl eye like occelations on the carapace, as well as several rows of tubercles, both of which are absent in the adult animals{4}. In regards to tail length the species is sexually dimorphic, with males possessing longer & thicker tails than the females{4,7}. They are moderately sized softshells; in his book Turtles of the world(1989), Carl Ernst states that the species can a carapace measuring up to 70cm(27.5in){4}. Animals collected in the Barak Valley of Northeastern India ranged from 14-57cm(5.5-22.4in) in Straight Carapace Length, and weighed 0.4-20kg(0.8-44lbs), undoubtedly containing young and adult animals{5}.
Geographic distribution & Habitat use
The Ganges softshell is not restricted to this particular river, and indeed inhabits multiple river systems, including the Indus & the Mahandi systems, which extend to Pakistan, Bangladesh, and Nepal{4}. They prefer turbid waters, which allow them to avoid detection from aerial predators, a benefit more useful for the younger animals. These waters allow them to camouflage into their surroundings, allowing them to ambush their prey easier as well. Ganges softshells are known to frequent sandy banks as well as the more muddy banks, areas that allow them to bask{4,6}.
Dietary habits
In his book Ernst(1989) notes that they take amphibians, fish and carrion, but also eat aquatic plants. Other more recent Authors have stated that this softshell is more plant based in its dietary habits. Fascinating predatory accounts have been published however, Rom Whitaker wrote on how he observed a small individual attack a frog as big as or bigger than itself, pull it under water, only to lose it as the turtle resurfaced for air{8}. Something more intriguing is the witnessed attack of an adult nilgai by numerous turtles, which failed to escape from the water after these turtles converged on it; One individual was recorded attacking a dog, and after the unfortunate canine was in the water it shared a similar fate to the ungulate{9}. These turtles may also be serious predators of the coot, one observation published in 2006 detailed how one was pulled underwater and drowned, likely by an Indian softshell as they had been reported basking on mud banks in the vicinity prior to the event{10}.
Reproduction
Ernst(1989) briefly wrote on nesting and clutch size of the species,writing that the nesting season in natural environments lasts from October to November, and that the eggs measured 23-32mm in diameter.(0.9-1.2in){4}. A more detailed study on the reproduction and clutch sizes has been published, this one covering a fifteen year period. Clutch sizes ranged from 6-35 with an average of ~18. The eggs averaged a length of 30.6mm(1.2in) and had an average width of 30.22mm(1.18in); the average weight of an egg was around 16g(0.56oz). Clutch size doesn't significantly differ between the wet and dry season, deviating by 2-3 eggs for the most part but sometimes as many as 9. Temperatures for the incubation of the eggs was generally held at 28-31°C, thoug ranged from 23-31°C with periods of time where the eggs were chilled in a refrigerator, to simulate natural temperature fluctuations clutches are exposed to in wild environments, and brought back to temperature.
In the aforementioned study on the clutch size and other reproduction related traits, the females were never paired with a male and had stored sperm for nearly fifteen years, perhaps the longest amount of time any reptile{11}.
References
{1}Noureen, U. and Khan, A. (2007). Freshwater turtles of Pakistan: a preliminary assessment of their status in Punjab and Sindh. A research report submitted to the Ministry of Environment’s Pakistan Wetlands Programme. pp 23
{2}Vyas, Raju. "Status of Ganges Soft-shell Turtle Nilssonia gangetica amidst Deplorable Scenarios In Urban Wetlands of Central Gujarat State, India." Newsletter of the South Asian Reptile Network 17 (2015): 3.
{3}Rao, R. J. "The Diversity, Ecology and Conservation Management of Freshwater turtles in Ganges River System."
{4}Ernst, Carl H., R. G. M. Altenburg, and Roger W. Barbour. Turtles of the world [CD-ROM]. 1998.
{5}Das, K. C., and A. Gupta. "Site records of softshell turtles (Chelonia: Trionychidae) from Barak Valley, Assam, northeastern India." Journal of Threatened Taxa 3.4 (2011): 1722-1726.
{6}Tripathi, Ashish, and Sushil K. Upadhyay. "DEMOGRAPHY OF FRESH WATER TURTLES IN CONFLUENCE AREA OF FIVE RIVERS (PANCHNADA) OFF NORTHERN INDIA." (2015).
{7}Baig, Khalid Javed, Rafaqat Masroor, and Mohammad Arshad. "Biodiversity and ecology of the herpetofauna of Cholistan Desert, Pakistan." Russian Journal of Herpetology 15.3 (2008): 193-205.
{8} Whitaker, Romulus, and Indraneil Das. The world of turtles and crocodiles. National Book Trust, 1993.
{9}Singh G.R. 2000. Ganges soft-shell turtle Aspideretus gangeticus predating on nilgai Boselaphus tragocamelus
in Keoladeo National Park, Bharatpur, Rajasthan. J. Bombay Nat. Hist. Soc. 97, part 2: 285
{10}van den Hout, Piet J. "Dense foraging flotillas of Eurasian Coots Fulica atra explained by predation by Ganges soft-shell turtle Aspideretus gangeticus." ARDEA-WAGENINGEN- 94.2 (2006): 271.
{11}Whitaker, N. I. K. H. I. L. "Immaculate conception, incubation protocols, and egg characteristics of the Ganges softshell turtle (Aspideretes gangeticus)." Contemporary Herpetology 2006 (2006): 1-6.
