Some Trionychidae turtles are highly prized as food, but others have been strictly protected in Asia for religious reasons. In fact, for several centuries Muslims have maintained a swamp with Nilssonia gangetica in Orissa, India, and another, with Nilssonia formosa, exists in Mandalay.
A third collection of sacred turtles is found in Chittagong, Bangladesh. This is Nilssonia nigricans. These turtles are often very tame and, if called upon, they also come to take food from the hand. On the other hand, in some parts of Africa, the winged tortoise of Senegal serves almost as a natural means of water purification.
In fact, it is placed in the sources so that it can eat any waste that falls into it. Little is known about the reproductive habits of soft-shelled turtles. In North America, nests are prepared in spring or early summer, when the females leave the water to dig their nests in the soil.
These nests are similar to those of many other turtles. In fact, these are holes dug in the shape of a flask, the depth of which corresponds to the maximum effort that can be made by the legs of the turtle, ie about thirty cm.
On average, there are 10-25 eggs, round and white, which are laid in the nest and covered, but it is not known how long the incubation period lasts, even if some eggs do not hatch until the following spring. Soft-shelled turtles were used as a reference and graphic inspiration in an episode of The Amazing World of Gumball in which their particular aggression is also enhanced.
Like other carnivorous freshwater turtles, soft-shelled turtles typically feed on a wide variety of food, including plants, carrion, and live animals. Instead, the spiny soft-shelled turtle feeds mainly on freshwater shrimp and aquatic insects, but it is doubtful that it will harm fishermen using the traditional hook and bait, as some claim.
The jaws of these turtles seem fragile, but it is only an appearance, as they are hidden by full lips: they are actually very strong. It should be noted that in some species the jaws show a very sharp edge, suitable for catching fish, while others have jaws with surfaces that are better suited for breaking up the shells of molluscs.
Soft-shelled turtles are different from other turtles precisely because their shells are covered with a layer of leathery skin instead of horny scales. This shell is flat and almost circular, which is why they are sometimes also called 'pancake turtles'
The jaws are hidden by full lips and the muzzle protrudes into a tube-like proboscis. The fourth and fifth toes are elongated, without claws and webbed to form spatulas.