Asian giant softshell turtle

For other species with similar names, see Giant softshell turtle.

The Asian giant softshell turtle (Pelochelys cantorii),^[1][2] also known commonly as Cantor's giant softshell turtle^[2] and the frog-faced softshell turtle, is a species of freshwater turtle in the family Trionychidae. The species is native to Southeast Asia. The species is critically endangered and in the 20th century has disappeared from much of its former range.

Asian giant softshell turtle
Conservation status
Critically Endangered  (IUCN 3.1)[1][2]
CITES Appendix II (CITES)[3]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Testudines
Suborder:	Cryptodira
Family:	Trionychidae
Genus:	Pelochelys
Species:	P. cantorii
Binomial name
Pelochelys cantorii Gray, 1864[1][2]
Range
Synonyms[4]
List Pelochelys cantorii Gray, 1864 Pelochelys cumingii Gray, 1864 Pelochelys cantoris Boulenger, 1889 Pelochelys poljakowii Strauch, 1890 Pelochelys cummingii M.A. Smith, 1931 (ex errore) Pelochelys cantori Pritchard, 1967 (ex errore)

Taxonomy

P. cantorii is not found in New Guinea, while the two other members of the genus Pelochelys, P. bibroni and P. signifera are both restricted to New Guinea.^[2] P. cantorii is relatively unstudied, and the current species may actually be composed of several taxa.^[5] One study from 1995^[6] showed that what was once thought to be P. cantorii in New Guinea was actually P. bibroni, and the earlier studies^[7][8] of P. cantorii only described populations farther to the west. The classification of P. cantorii is Family: Trionychidae, Order: Testudines. A genome study revealed that several genes related to tumor resistance, growth, and aging were more active in P. cantorii. The genes found were VWA5A, ABCG2, A2M, and IGSF1.They are related to tumor resistance, growth, and aging. P. cantorii fits into turtle evolution because P. cantorii became separate from its closest turtle relatives about 59 million years ago. Turtles split from the common ancestor of birds and crocodiles around 256 million years ago.

Description

The Asian giant softshell turtle has a broad head, and small eyes close to the tip of its snout. The carapace is smooth and olive-colored. Juveniles may have dark-spotted carapaces and heads, with yellow around the carapace.^[5]

Despite reports that it can grow up to 1.8 metres (5.9 ft) in length and is the world's largest extant freshwater turtle, this maximum size and title is murky at best.^[9][10] Apparently the largest specimen carapace length, 129 cm (51 in), known is considered suspect and the heaviest specimen known (weighing approximately 250 kg (550 lb) was actually a misidentified Yangtze giant softshell turtle.^[11][12] A more realistic range of carapace length for this species is reportedly 70 to 100 cm (28 to 39 in) and it is one of about a half-dozen giant softshell turtles from three genera that reach exceptionally large sizes, i.e. in excess of 100 kg (220 lb) in mass.^[13]

Behavior and reproduction

P. cantorii is an ambush predator and primarily carnivorous, feeding on crustaceans, mollusks and fish (although some aquatic plants may also be eaten).^[5] The turtle spends 95% of its life buried and motionless, with only its eyes and mouth protruding from the sand. It surfaces only twice a day to take a breath, and lays 20–28 eggs sized around 3.0 to 3.6 centimetres (1.2 to 1.4 in) in diameter in February or March on riverbanks.^[5][10][14]

Morphological variation

Asian giant softshell turtle at the Philippine National Museum

Morphological differences in neural bone count have been noted between specimens of P. cantori found in the Philippines and specimens found in mainland Asia.^[15]

Etymology

The specific name, cantorii, is in honor of Danish zoologist Theodore Edward Cantor.^[16] Additionally, they are named for their softshells because they have soft, leathery shells that are completely devoid of scales.

Geographic range and habitat

The species P. cantorii is primarily found in inland, slow-moving, freshwater rivers and streams. Some evidence indicates that its range extends to coastal areas, as well.^[5] It occurs in eastern and southern India, Bangladesh, Burma, Thailand, Malaysia, Laos, Cambodia, Vietnam, eastern and southern China, the Philippines (Luzon and Mindanao), and Indonesia (Kalimantan, Java, and Sumatra).^[2]

Conservation

The Asian giant softshell turtle is classified as a Critically Endangered by the IUCN and has been forced out through habitat destruction, disappearing from much of its range.^[17] Prior to 2007, it was last seen in Cambodia in 2003. A 2007 survey of one area of the Mekong River in Cambodia found the turtle in abundance along a 48 kilometres (30 mi) stretch of the river.^[10][18]

In the Philippines, a juvenile Cantor's turtle known as "cagot" appeared and was captured by a fisherman along the Addalam River, Cabarroguis, Quirino, Isabela. In 2001, this turtle was sent to Chicago and its identity confirmed.^[19] The reptile has been evaluated as an EDGE species by the Zoological Society of London.^[20]