Caspia knipowitschii Makarov, 1938

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 : 53-54

Caspia knipowitschii Makarov, 1938

( Figures 1 A–I, 3A–D, 5A–D)

Caspia gmelini var. knipowitschii Makarov, 1938: 1058 (description, no figure);

Pyrgula (Caspia) knipowitchi (sic) ( Makarov, 1938) – Golikov and Starobogatov 1966: 354, fig. 1, 6;

Caspia knipowitschi Makarov, 1938 – Golikov and Starobogatov 1972: 99, pl. 2, fig. 17;

Caspia (Clathrocaspia) knipowitschi knipowitschi Makarov, 1938 – Alexenko and Starobogatov 1987: 36;

Caspia (Clathrocaspia) knipowitschi Makarov, 1938 – Anistratenko 2007b: 796–797, fig. 2, 19.

The teleoconch is conical low-spired in shape, thick-walled, minute. The shell consists of 4.0–4.5 weakly inflated whorls with regularly increasing diameter; up to about 2.2–2.3 mm in height and up to 1.3 mm in width. The apical angle ranges from 45 ◦ to 50 ◦, spire profile slightly convex. A slightly incised suture separates the whorls, ornamented with fine but distinct spiral ribs (up to 15–17 on body whorl), crossed by weaker raised axial lines, resulting in a reticulate pattern ( Figure 1 A–E) characteristic of all known Caspia in the Azov–Black Sea Basin (see also Anistratenko 2007a). Body whorl moderately expanded, occupying about 0.75 of total shell height. Aperture medium-sized, drop-shaped, outer lip thickened especially in posterior part. Height of shell is 2.5 times the height of aperture. The umbilicus is usually narrow and chink-like or closed.

The protoconch is comparatively large ( Figure 1E,F,H,I ), dome-like, consists of 1.25–1.30 whorls and has a maximum diameter of 0.34–0.35 mm; diameter of the first embryonic whorl is 0.30–0.31 mm. The initial cap-like onset of the embryonic shell is 0.13–0.15 mm wide. The most remarkable feature of the protoconch is the densely reticulated fine ornamentation that covers the entire surface of embryonic shell. Usually this sculpture covers the surface more or less regularly, though sometimes delicate but distinct spiral rows of grains can be recognized ( Figure 1F,H,I ). The transition from the protoconch to the teleoconch is well marked by a slight thickening, followed by a constriction. The teleoconch sculpture begins with weak spiral grooves, which become more prominent and turn into ribs during the course of the first 0.5–1.25 teleoconch whorls.

Figures

Figure 1. Caspia knipowitchii: (A) apertural view of the adult shell; (B, C) apical and lateral views of the protoconch of the same specimen as in A; (D) apertural view of the juvenile shell; (E, F) detailed lateral views of the embryonic shell of the same specimen as in D; (G) apical view of the protoconch of the same specimen as in D; (H, I) close-up of the same embryonic shell as in D: specific fine reticulate sculpture on the surface of the embryonic shell are seen, WE, width of initial cap-like part of embryonic shell.