''Villorita cyprinoides'', the black clam, is found in the backwaters of
Kerala
Kerala ( ; ) is a state on the Malabar Coast of India. It was formed on 1 November 1956, following the passage of the States Reorganisation Act, by combining Malayalam-speaking regions of the erstwhile regions of Cochin, Malabar, South ...
, mainly in Vembanad backwaters. This species occurs in salinity range of 3 ppt in August to 16 ppt in May and the
dissolved oxygen
Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...
content ranged from a high of 6.5 ml/L during August–November to a low of 2.83 ml/L in February. The black clam attains sexual maturity at a length of . It does not show sex reversal or
hermaphroditism
In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes.
Many taxonomic groups of animals (mostly invertebrates) do not have separ ...
. It spawns twice a year, from May to August, and from January to late March. A change in
salinity
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
is the most important factor that triggers spawning, while
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
is not a factor. The optimum salinity for spawning is about 10–12 ppt.
The species is harvested extensively from the wild population and this could be potential threat to this species. Other recorded threats are closure of the Thaneermukham Barrage near Vambanad Lake, frequent dredging, pollution from
effluent
Effluent is wastewater from sewers or industrial outfalls that flows directly into surface waters either untreated or after being treated at a facility. The term has slightly different meanings in certain contexts, and may contain various pollut ...
s from shrimp processing plants/factories,
ecotourism
Ecotourism is a form of tourism involving responsible travel (using sustainable transport) to natural areas, conserving the environment, and improving the well-being of the local people. Its purpose may be to educate the traveler, to provide funds ...
and
Water Hyacinth
''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth is an aquatic plant native to South America, naturalized throughout the world, and often invasive outside its native range.Cyrenidae
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