Melanopsis (Melanopsis etrusca)

Description

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Melanopsis fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Melanopsis description

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 biology

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⁾.

Melanopsis range

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⁾.

Melanopsis habitat

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⁾.

Melanopsis status

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

Melanopsis threats

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 conservation

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⁾.

Find out more

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/

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Glossary

Algae

Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.

Detritus

Litter formed from fragments of dead material.

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Larval

Of or relating to the immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.

Mantle

In molluscs, a fold of skin that encloses a space known as the mantle cavity, which contains the gills. The mantle is responsible for the secretion of the shell.

Molluscs

A diverse group of invertebrates, mainly marine, that have one or all of the following: a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.

Operculum

In some snail species, a horny or calcareous plate that is attached to the foot and used to close the shell aperture when the soft parts of the body are retracted.

Oviparous

An animal that reproduces by laying eggs, which hatch outside the mother’s body.

Whorl

In animals, a spiral or coil in the shell of a snail.

References

1. IUCN Red List (December, 2011)
   http://www.iucnredlist.org/
2. Altaba, C.R. (1998) Testing vicariance: melanopsid snails and Neogene tectonics in the Western Mediterranean. Journal of Biogeography, 25: 541-551.
3. Oscoz, J., Galicia, D. and Miranda, R. (2011) Identification Guide of Freshwater Macroinvertebrates of Spain. Springer, Berlin.
4. Lev, L., Boaretto, E., Heller, J., Marco, S. and Stein, M. (2007) The feasibility of using Melanopsis shells as radiocarbon chronometers, Lake Kinneret, Israel. Radiocarbon, 49(2): 1003-1015.
5. Strong, E.E., Colgan, D.J., Healy, J.M., Lydeard, C., Ponder, W.F. and Glaubrecht, M. (2011) Phylogeny of the gastropod superfamily Cerithioidea using morphology and molecules. Zoological Journal of the Linnean Society, 162: 43-89.
6. Dudgeon, D. (1999) Tropical Asian Streams: Zoobenthos, Ecology and Conservation. Hong Kong University Press, Hong Kong.
7. Gherardi, F. (2007) Biological Invaders in Inland Waters: Profiles, Distribution and Threats. Springer, Berlin.