The tadpole-gobies (Benthophilus), also called pugolovkas (which means "tadpole" in Russian), are a genus of Ponto-Caspian fish in the family Gobiidae.
They are distributed in the fresh and brackish waters of basins of the Black Sea, Caspian Sea and the Sea of Azov, up to salinities of about 20 ‰. They typically live in habitats such as the deep waters of the Caspian (salinity about 13 ‰) and in the deltas, estuaries and coastal waters of the Ponto-Caspian.
Tadpole-gobies are small fish, never larger than 15cm (5.9in), and usually smaller. Their life span is about one year. After spawning they die.
Species
There are currently 21 recognized species in this genus:
Genetic studies in the Volga-Kama basin have revealed that invasive populations consist of a mixture of two phylogenetic lineages. One lineage, widely distributed in the new range, is genetically identical to the Don tadpole-goby (Benthophilus durrelli), likely introduced accidentally during historical mysid acclimatization efforts from the Azov basin. The second lineage, of Caspian origin, corresponds to Benthophilus stellatus sensu stricto, making the Lower Volga a mixing zone for these distinct genetic groups.
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