Viviparidae

Top mud snail ( Viviparus contectus ), housing

River snails ( Viviparidae ) are a (except South America and Antarctica ) worldwide distributed family living in freshwater snails, which is made to the order of Architaenioglossa.

Features

The housing is comparatively large, having up to 5 cm; the river snails are a thing together with the pond snail of the largest Central European freshwater snails. You have a fixed lid (operculum ), which is rooted at the base. With this cover you can close the thick chassis. This closure plays an important role in the winter.

River snails are viviparous. Referred to by its scientific name also Viviparus. In Central Europe, they are the only live-bearing snails.

Reproduction

Viviparidae are dioecious, hermaphrodite, like many other species of snails. The right sensor of the male is shorter and more thickened than the left ( the sensor of the females have the same thickness ). This sensor contains the copulatory organ, so that the sperm are placed in the female genital opening. The eggs develop in an enlarged end portion of the female ovary. There, the embryos feed on a protein-rich fluid. There are in a mother usually several young animals in different stages of development. The oldest animal is then born individually ( ovoviviparous ). The young snails are fully developed at birth, up to 10 mm in size (usually 4 mm ) and have bristles on their body, which fall off later.

Lifestyle and diet

River snails have received their German names from the river snails of the genus Viviparus (see below), but are in their entirety mainly ground dwellers moving waters ( lowland rivers, shore zones of lakes). They crawl around on the floor and mostly on stones and wood; rare in plants. In the aquarium they also crawl rarely high on the disc, which may change if the disks are heavily overgrown with algae. Species from calmer waters dig a hour in the sand or mud. River snails have a wide food spectrum. They graze algae and bacteria from grass, eating detritus and decaying plants and are also capable of using a mucus network, which is formed at the base gills, food particles and plankton to filter out of the water. After some time tearing the network is clumped and transported from the mantle cavity. Then the clumped mucus net is eaten including food particles. This food acquisition by filtration is very unusual for freshwater snails.

The European species tolerate relatively high temperatures above 25 ° C.

System

There are many fossil species are known; tart are several dozen species worldwide. Earlier, the family Viviparidae became the order means snails ( Mesogastropoda ) provided. The center screw included to turn the subclass prosobranch ( Prosobranchia ). In the system out here, there are three subfamilies with the following genera:

• Viviparinae Viviparus (eastern North America and Europe). The genus is divided by many authors in several subgenera.
• Tulatoma ( endemic to the Coosa River, Alabama )

• Campeloma
• Lioplax (both widespread in eastern North America ),

• Angulyagra (China and Southeast Asia)
• Bellamya (Africa)
• Cipangopaludina ( East Asia, especially Japan, Korea, China and Vietnam, partially naturalized elsewhere )
• Filopaludina ( Southeast Asia and China)
• Idiopoma ( Southeast Asia and China)
• Larina ( northeast Australia )
• Margarya (China: Yunnan )
• Notopala ( eastern Australia )
• Sinotaia (China)
• Taia (Burma)
• Trochotaia (Thailand)

The delimitation of genera within each form rich Asian Bellamyinae is currently often contentious.

In Europe, only genus Viviparus lives with five species. After this genus the river snails ( Viviparidae ) are scientifically named.