CASPIINAE B. Dybowski, 1913

Anistratenko, Vitaliy V., 2013, On the taxonomic status of the highly endangered Ponto-Caspian gastropod genus Caspia (Gastropoda: Hydrobiidae: Caspiinae), Journal of Natural History 47 (1 - 2), pp. 51-64 : 60-61

Subfamily CASPIINAE B. Dybowski, 1913 .

The hydrobiid subfamily Caspiinae contains the genus: Caspia with the subgenera Clathrocaspia Lindholm, 1929 and Ulskia Logvinenko and Starobogatov, 1969 .

The Caspia species here studied belong to the subgenus Clathrocaspia Lindholm, 1929 (type species Caspia pallasii Clessin and W. Dybowski in W. Dybowski, 1887) which is distinguished from the species of Caspia s.str. (type species Caspia baerii Clessin and W. Dybowski in W. Dybowski, 1887) by the development of a reticulate teleoconch sculpture. Although the characters of the protoconch, radula and genital morphology of Caspia baerii and other species of Caspia s. str. are not known, the assignment of species to Caspia , including Clathrocaspia , is based on the general characters of the shell (see diagnosis of Caspiinae below). We continue to maintain this assignment at this stage, pending further studies of the remaining species currently assigned to Caspia and Clathrocaspia . On the basis of the data presented here, the subfamily diagnosis of Caspiinae is tentatively modified as follows.

Caspiinae are characterized by the combination of the following characters: a small (height 2–5 mm) conical to ovate-conical shell with modestly convex whorls, a closed or chink-like umbilicus, absence of an angle between columellar and palatal margin and an abapically protracted apertural margin; the protoconch shows well-developed pitted ornamentation similar to most Hydrobiidae ; radula with two pairs basal cusps on the rachidian tooth of the radula; in the female genitals both a bursa copulatrix and a seminal receptacle rs-1 are absent.

The presence of two pairs of basal denticles on the rachidian tooth suggest classification of Caspiinae in Hydrobiidae as a distinct subfamily. Hydrobiinae differs from Caspiinae by the presence of one or two pairs of basal denticles on the rachidian tooth and having both a bursa copulatrix and seminal receptacle; the Ponto-Caspian genus Caspiohydrobia belongs here. Pyrgulinae differs from Caspiinae by the absence of basal denticles on the rachidian tooth, and the presence of a bursa copulatrix whereas a seminal receptacle rs-1 is absent. Representatives of Turricaspiinae differ from all listed taxa by the absence of basal denticles on the rachidian tooth, and the presence of both a bursa copulatrix and a seminal receptacle rs-1 (see Anistratenko 2008). From a phylogenetic point of view Caspiinae might be considered as having more derived characters then the other taxa here discussed. Their representatives have lost the bursa copulatrix and the seminal receptacle, while retaining as ancestral hydrobiid radular traits the basal denticles on the rachidian tooth. Pyrgulinae and Turricaspiinae retain some of the more common characters of their ancestor.

Several collecting efforts have been made by the author in the Azov–Black Sea Basin in the past decade, and other collection efforts have been made by Th. Wilke and Ch. Albrecht (personal communication) in the Caspian Sea to search for living Caspia -like hydrobiids. The latter provided no living material. Nor have live specimens been found by F. Wesselingh (personal communication) in samples from the western Caspian coast. The Azov–Black Sea collection trips reported on the very rare occurrence in very few places of these taxa, suggesting a rare and very discontinuous modern distribution. Such distribution types add to the concern over the decline of this group .

This study shows that not only individual species of Caspia , mainly restricted to a few localities, but the entire subfamily Caspiinae might be critically endangered. Factors contributing to the demise of this group, including habitat deterioration and invasive species, need urgent assessment. This paper provides data for the taxonomic base for such efforts. The potential loss of this endemic group of snails would terminate millions of years of evolutionary history of a part of Ponto-Caspian biodiversity.