| Trionychidae | |
|---|---|
| Chinese softshell turtle Pelodiscus sinensis |
|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Subclass: | Anapsida |
| Order: | Testudines |
| Suborder: | Cryptodira |
| Superfamily: | Trionychoia |
| Family: | Trionychidae Fitzinger, 1826 |
| Subfamilies | |
Trionychidae is a taxonomic family which comprises a number of turtle genera commonly known as softshells. They are also sometimes called pancake turtles. Softshells consist of some of the world's largest fresh water turtles, though many can adapt to living in highly brackish areas. Members of this family occur in Africa, Asia, North America, and Southeast Asia. North American members of genus Trionyx were fairly recently (1987) assigned the resurrected genus name Apalone by Meylan,[2] though they are still listed semi-correctly as Trionyx in some texts.
Contents |
They are called "softshell" because their carapace lacks horny scutes (scales), though the spiny softshell, Apalone spinifera, does have some scale-like projections, hence its name. The carapace is leathery and pliable, particularly at the sides. The central part of the carapace has a layer of solid bone beneath it, as in other turtles, but this is absent at the outer edges. Some species also have dermal bones in the plastron, but these are not attached to the bones of the shell. The light and flexible shell of these turtles allows them to move more easily in open water, or in muddy lake bottoms.[3]
Females can grow up to several feet in carapace diameter, while males stay much smaller; this is their main form of sexual dimorphism. Pelochelys cantorii, found in southeastern Asia, is the largest softshell turtle on earth.
These turtles have many characteristics pertaining to their aquatic lifestyle. Like all aquatic turtles, they need to be submerged to be able to swallow food. Most are strict carnivores, with diets consisting mainly of fish, aquatic crustaceans, snails, amphibians,[3] and sometimes birds and small mammals. They have elongated, soft, snorkel-like nostrils. Their necks are disproportionately long in comparison to their body size, enabling them to breathe surface air while their bodies remain submerged in the substrate (mud or sand) a foot or more below the surface.
Like some amphibians and marine snakes, softshells are able to extract a small amount of oxygen out of water via their skin, further enabling them to stay underwater for prolonged periods.[4] Their feet are webbed and are three-clawed, hence the "Tri-" in the genus name. The carapace color of each type of softshell turtle tends to match the sand and/or mud color of its geographical region, assisting in their "lie and wait" feeding methodology.
Softshells can move at speeds of up to 15 miles per hour. The mandibles of many species form the outer border of powerful crushing processes- the alveolar surfaces of the jaws - believed to aid the ingestion of tough prey such as molluscs. These jaws make large turtles dangerous as they are capable of amputating a man's finger - possibly his hand."[5]
Softshell turtles are eaten as a delicacy in most parts of their range, particularly in East Asia. Chinese people, in particular, enjoy eating them with chicken in stew. According to a 1930 report by Soame Jenyns, Guangdong restaurants had them imported from Guangxi in large numbers; "eaten stewed with almonds, roast with chili sauce or fried with bamboo shoots, they [were] considered a great delicacy."[6]
World-wide, the most commonly consumed softshell species is the Chinese softshell Pelodiscus sinensis. As a noted Japanese biologist pointed out in 1904, the Japanese variety of this turtle, which at time was classified as Trionyx japonicus, occupied a place in Japanese cuisine as esteemed as the diamondback terrapin in the United States or the green turtle in England. The farming of this "luscious reptile", known in Japan as suppon, was already developed on an industrial scale in that country by the late 19th century.[7]
Due to raising demand and overhunting, the price of Pelodiscus sinensis in China skyrocketed by the mid-1990s; large-scale turtle farming in China and neighboring countries, raising this species by hundreds of millions was the response, with prices soon returning to a more affordable level.[8][9][10] Another species, Palea steindachneri, is farmed in China as well, but on a much smaller scale (with farm herds measured in hundreds of thousands, rather than hundreds of millions).[10]
In the United States, "harvesting" softshell (e.g. Apalone ferox) until recently was legal in Florida. Environmental groups have been advocating with the authorities for banning, or restricting, the practice. The Florida Fish and Wildlife Conservation Commission responded by introducing the daily limit of 20 turtles per day for licensed harvesters - the level which the turtles advocates consider unsustainable, as there may be anywhere between 100 to 500 hunters state-wide. While some catch was consumed locally, most was exported; the Commission estimated (2008) that around 3,000 pounds of softshell turtles were exported each week via Tampa International Airport.[11]
After meetings and discussions with a diverse group of stakeholders, commission staff decided to propose a ban on commercial take of freshwater turtles. Further study revealed there is a potential for a commercial market to impact freshwater turtle populations through too much harvest pressure, which in turn could threaten the sustainability and the unique diversity of turtles in Florida. The new rules, in effect as of July 20, 2009, restrict collecting any wild turtles to one turtle per person per day, completely prohibit collection of softshells (Apalone) in May through July, and prohibit trade in turtles caught from the wild. An exemption is provided for licensed turtle farms that need to catch turtles in the wild to serve as their breeding stock.[12]
Some other U.S. states, too, have already adopted strict limitations on wild turtle trade. In 2009, South Carolina passed the law (Bill H.3121) restricting interstate and international export of wild-caught turtles (both soft-shell and some other species) to 10 turtles per person at one time, or 20 turtles per person per year.[13]
Family Trionychidae
Cladogram after Walter G. Joyce, Ariel Revan, Tyler R. Lyson and Igor G. Danilov (2009).[14]
| Trionychidae |
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Parade of the Animal Kingdom. Hegner, Robert. 1935. the Macmillan Company.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||