Bithynia (Bithynia zeta)

Bithynia zeta shells
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Bithynia fact file

Bithynia description

GenusBithynia (1)

Described as recently as 2007, the freshwater mollusc Bithynia zeta is named after the country of Zeta, which existed around Lake Skadar in the 11th to 13th century (2).

The greyish-yellow shell of Bithynia zeta consists of 4.5 convex whorls and has an oval-shaped aperture. The width of the shell is variable, and the male and female of this species are very similar (2).

Male molluscs within the Bithyniidae family have a well-developed penis (3), which in Bithynia zeta is tapered and has a pointed tip (2). Like other members of the Bithyniidae (4), the penis of Bithynia zeta has an accessory appendage, which is shorter than the penis itself (2).

In order to seal off the shell to protect themselves from predators, members of the Bithyniidae family have a calcareous operculum (3) (5).

Shell height: 4 - 5 mm (2)

Bithynia biology

Very little is known about the specific biology of Bithynia zeta, but it is assumed to be similar to other species within the Bithyniidae family.

Most species within the Bithynia genus are primarily thought to be filter feeders, but are known to switch to grazing when blooms of algae occur in the spring, or if the concentration of food particles suspended in the water decreases (6).

In some species of Bithyniidae, food particles are filtered through a net of mucus and become trapped before being ingested (3) (5).

Most Bithyniidae species have an annual life cycle, and can live for approximately three years (3). The female is oviparous (4), and the eggs are laid in small clusters (5). The eggs have exit holes which are used when the juveniles hatch (4), but these are closed off during development with a capsule or plug (4) (5).


Bithynia range

Bithynia zeta is endemic to a single lake, Lake Skadar, on the border of Montenegro and Albania. This species is only known from five different sites in the lake (1).


Bithynia habitat

Bithynia zeta is a freshwater mollusc species. It lives under stones on mud substrate in Lake Skadar, close to the shore (1) (2).


Bithynia status

Bithynia zeta is classified as Endangered (EN) on the IUCN Red List (1).

IUCN Red List species status – Endangered


Bithynia threats

Ecosystem degradation is one of the key threats to Bithynia zeta. Lake Skadar is currently undergoing rapid eutrophication, and water from some of the springs on the lake bottom which feed into the lake is being captured as drinking water for local communities. This could eventually impact the water levels of the lake (1).


Bithynia conservation

There are currently no known conservation actions in place for Bithynia zeta. However, several projects focussing on ecosystem management within the Lake Skadar area are being carried out (1).

Recommended future actions include conducting more research on the population size and distribution of Bithynia zeta, as well as on habitat trends (1).


Find out more

For further information on the conservation of freshwater habitats and biodiversity see:



This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:



Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
The main opening in the shell of certain molluscs, from which the soft, internal body parts emerge.
Containing calcium carbonate, chalky.
A species or taxonomic group that is only found in one particular country or geographic area.
A process in which a water body is enriched with excessive nutrients (such as nitrogen and phosphorus) resulting in the excessive growth of aquatic plants and the depletion of oxygen, creating unfavourable conditions for other organisms, such as fish.
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
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.
An animal that reproduces by laying eggs, which hatch outside the mother’s body.
In animals, a spiral or coil in the shell of a snail.


  1. IUCN Red List (November, 2011)
  2. Glöer, P. and Pešic, V. (2007) The Bithynia species from Skadar Lake (Montenegro) (Gastropoda: Bithyniidae). Mollusca, 25(1): 7-12. Available at:
  3. Oscoz, J., Galicia, D. and Miranda, R. (2011) Identification Guide of Freshwater Macroinvertebrates of Spain. Springer, USA.
  4. Brown, D.S. (1994) Freshwater Snails of Africa and their Medicinal Importance. CRC Press, USA.
  5. Dudgeon, D. (1999) Tropical Asian Streams: Zoobenthos, Ecology and Conservation. Hong Kong University Press, Hong Kong.
  6. Dillon, R.T. (2000) The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge.

Image credit

Bithynia zeta shells  
Bithynia zeta shells

© Peter Gloeer

Peter Gloeer


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