Theodoxus pallasi Lindcholm, 1924
Conservation status: in Bulgaria: Extinct EX.
General distribution. The Aral Sea, the Caspian Sea and the strongly freshened parts of the Sea of Azov. In the Black Sea it has been discovered as a subfossil (empty shells), found in the firths of the rivers flowing into the sea; a Caspian relict .
Distribution and abundance in Bulgaria. Found with many individuals in Varna lake, on the stones near the quarries . The last living individuals were registered at depths of 4 to 10 m in 1957 . Living individuals have not been found in other regions of the country. During the last 4 decades, Varna lake was subjected to profound anthropogenic changes that led to the disappearance of the species.
Habitats. Shore brackish and freshwater lagoons and lakes; estuary waters.
Biology. It feeds on mushrooms and water plants.
Similar species. Theodoxus fluviatilis, T. danubialis, T. euxinus, T. pilidei and T. transversalis, from which it differs with its specific colouring.
Negative factors. Loss and degradation of habitats: industry, water transport, infrastructure development, pollution of the waters.
Conservation measures taken. None.
References. 1. Kaneva-Abadzhieva, 1957; 2. Drensky, 1947.
Author: Zdravko Hubenov