Melanopsis  (Melanopsis etrusca)

Melanopsis etrusca is classified as Endangered (EN) on the IUCN Red List (1).

A member of the Melanopsidae family, Melanopsis etrusca is a fairly large freshwater snail which, like other species in the family, has an unusually thick and heavy shell (2). The last whorl of the solid shell is relatively large, and melanopsids have a horny operculum which retracts inside (3).

The shell of Melanopsis species is generally dark, due to an organic coating which erodes quickly after the snail dies. The shell is formed from carbonate which is secreted from the snail’s mantle in the shell (4).

Melanopsis etrusca is a mollusc endemic to Italy, known only from four locations within southern Tuscany (1). It is the only melanopsid living in the Italian Peninsula (2). Over the last few decades this species’ range has declined, and it is now thought to occupy less than 400 square kilometres (1).

Thermal springs are the preferred habitat of Melanopsis etrusca, as it requires a constant supply of warm, clear water (1) (2). Melanopsids are known to live on hard substrates, but are also able to move over silt sediments (3).

Members of the Melanopsidae family are poorly documented (5). However, they are known to be detritus feeders, and also consume algae (3). Melanopsids are very sensitive to low temperatures (3), and are unable to withstand desiccation (drying out) or sudden changes or disturbances within their habitat (2).

Snails within the Melanopsidae family are oviparous (6), and the female is known to lay eggs in two different ways. Over gravel substrates, the female lays capsules with an average of 17 eggs, whereas individual, unprotected eggs are laid over sandy substrates (3). Melanopsid snails undergo direct development, which means that the eggs hatch directly into juveniles and there is no intermediate larval stage (2).

Removal of water from the sites in which Melanopsis etrusca lives is a major threat to this species (1), as it is unable to withstand desiccation (2). A large subpopulation located on a farm at Poggetti Vecchi is at high risk of extinction as a result of temporary drainage of the pool in which this mollusc species is found (1).

The high population density of the invasive red-rimmed melania (Melanoides tuberculata), a large freshwater snail which was first found in Italy in 1984, is expected to lead to an irreversible decline of Melanopsis etrusca as it may compete for food and space (7).

Melanopsis etrusca is a protected species in Tuscany, and is listed under Annexes A and B of the Tuscany Regional Law 56/2000. This means that the species itself is protected, and that its protection may require the designation of a Regional Important Site at the locations where it remains (1).

Further information on the conservation of freshwater habitats and biodiversity:

• WWF:
  http://www.panda.org/about_our_earth/about_freshwater/
• IUCN Red List Freshwater Initiative:
  http://www.iucnredlist.org/initiatives/freshwater
• IUCN Freshwater Biodiversity Unit:
  http://www.iucn.org/about/work/programmes/species/our_work/about_freshwater/