Hydrobiidae
Marstonia comalensis
The water snails ( Hydrobiidae ), also watt screw [Note 1] or Bithynias are a species-rich family from the group of Caenogastropoda. The very small to small snails can be found worldwide, especially in fresh water but also in brackish water and in some cases in seawater.
Features
Water snails have small, conical and smooth, right-handed body with a mostly oval, always ganzrandigen mouth. The shells of adult snails have 2-8 whorls and be no longer than 8 mm, but the house can always take up the whole, little snail. The horny operculum is spiral with a few turns.
The snails have a long, two-part snout and two filamentous, pointed or blunt probe, sitting at the base of the eyes. The coattails can be simple or be occupied with extensions. The foot consists of a front and rear half. The mucous gland is centered on the front edge of the foot. Head, foot, mantle and visceral sac are colored pale gray to dark purple or black melanin.
The mantle cavity contains almost the whole length of a gill, which consists of 10 to 200 triangular filaments. The osphradium is usually small.
The radula is of type Taenioglossa with more than fifty rows of teeth. The central tooth is trapezoidal and the posterior teeth usually provided with a few to many, the marginal teeth with many bumps.
The water snails are usually dioecious, with the male mated the female with his penis. The females lay their eggs in each egg capsules from, often to water plants, but it can also give Ovoviviparie. In this case, there is a direct development, but in general to slip in most species finished screw. In some species there is a development on veliger larvae.
Since the housing of the water snails have a few species-specific characteristics and at the same time many species are highly variable in itself, must be used in descriptions of species and species determinations on features of the operculum, the radula and penis.
Dissemination and lifestyle
Most water snails species live in freshwater, such as lakes or rivers, while other species are found in brackish water. A few species live in salt water, especially on sandy or muddy ground between algae or seagrass beds.
The snails live on algae and detritus.
Some species
In the North Sea and the Baltic Sea, the family, among others, by the congregation mud snail or Smooth mud snail ( Hydrobia ulvae ), the Bulbous mud snail ( Ecrobia Ventrosa ), the peak mud snail ( Hydrobia acuta) and the Overlooked mud snail ( Hydrobia neglecta ) is represented. Introduced from New Zealand in the North Sea is the New Zealand mud snail ( Potamopyrgus antipodarum ), and frequent in the Black Sea stone adhesive ( Lithoglyphus naticoides ) is also passed through the boat trip to Central Europe.
System
After Bouchet and Rocroi ( 2005), the family Hydrobiidae one of 19 families in the superfamily Rissooidea. To the family Hydrobiidae currently includes more than 160 genera:
- Adriohydrobia Radoman, 1973
- Akiyoshia Kuroda & Have, 1954
- Alzoniella Giusti & Bodon, 1984
- Andrusovia Brusina in Westerlund, 1903
- Antibaria Radoman, 1973
- Antillobia Alta, 1993
- Antroselates Hubricht, 1963
- Arganiella Giusti & Pezzoli, 1980
- Aroapyrgus H. B. Baker, 1931
- Avenionia Cossmann, 1900
- Badenia Finlay, 1930
- Belgrandia Bourguignat, 1869
- Birgella H. B. Baker, 1926
- Boetersiella Arconada & Ramos, 2001
- Boleana Radoman, 1973
- Bracenica Radoman, 1973
- Brachypyrgulina Haas 1955
- Dwarf spring snails ( Moquin - Tandon Bythinella, 1856) Austrian dwarf spring snail ( Bythinella austriaca )
- Rhön spring snail ( Bythinella compressa )
- Pannonian dwarf spring snail ( Bithynella pannonica )
- Husmanns fountain auger ( Bythiospeum husmanni )
- Common mud snail ( Hydrobia ulvae )
- New Zealand mud snail ( Potamopyrgus antipodarum )
- River - water snail ( Sadleriana fluminensis )
- Schmidt's water snail ( Sadleriana schmidtii )