Andrusovia dybowskii Brusina 1902
Creators: name: Anistratenko, Vitaliy V.
name: Neubauer, Thomas A.
name: Anistratenko, Olga Yu.
name: Kijashko, Pavel V.
name: Wesselingh, Frank P.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Hydrobiidae
Andrusovia
Andrusovia dybowskii

description: Andrusovia dybowskii Brusina in Westerlund, 1903
Figs 2, 3
Zagrabica Brusiniana nob.—Clessin & W. Dybowski in W. Dybowski 1887: 52–53 [partim, only shells <1 mm; others are Abeskunus brusinianus].
Andrusovia Dybowskii n. Brus.—Brusina in Westerlund 1903: 133.
Horatia [(Caspiohoratia)] marina Logv. et. Star. sp. n.— Logvinenko & Starobogatov 1969: 382, fig. 367(18).
Andrusovia dybowskii Brusina in Westerlund, 1903 — Starobogatov 2000: 39, fig. 1A.
Andrusovia andrusovi Starobogatov, sp. nov. — Starobogatov 2000: 39–41, fig. 1B.
Andrusovia brusinai Starobogatov, sp. nov. — Starobogatov 2000: 41, fig. 1C.
Andrusovia marina (Logvinenko et Starobogatov, 1969) — Starobogatov 2000: 41–42, fig. 1D.
non Andrusovia brusinai Starobogatov, 2000 — Neubauer et al. 2018: 54–56, fig. 6F–K, M, N.
Andrusovia dybowskii Brusina in Westerlund, 1903 — Anistratenko et al. 2019: 55–57, fig. 10A–J.
Type material. Previously, the syntype material of this species was presumed lost, but it was uncovered in the course of the present study in the “Caspian Mollusca” collection of the CNHM. The material consists of 37 specimens, which were split by Brusina into two tubes. A tube with four specimens bears the inscription “U.” in Brusina’s handwriting, which very likely means “unicum”, a term that Brusina often used to label type specimens in his col-lection (P. Crnčan, pers. comm. 06/2020). The handwriting on the labels of the material are near identical to the one on labels of the von Baer collection, confirming that the type material comes from that collection. Letters written by Brusina stored in the “Caspian Mollusca” collection of the CNHM prove that Władysław Dybowski sent material to Brusina after publication of his monograph on Caspian molluscs (W. Dybowski 1888: 53, 64 footnote). In a letter from Brusina to Benedykt Dybowski, along with which he sent material back to Lviv (dated 14 June 1905), he referred to the new species Andrusovia Dybowskii from “Detritus [...] aus 46 Sežen Tiefe”. This matches the label on the material in Zagreb (“I iz 46 sež. dub.”) as well as that on lot ZB-M W.Dyb. 116 (“ Detritus 46 Saž. tief”). These labels refer to a collection depth of 46 fathoms (Russian “sažen” or “sazhen”, Croatian “sežanj”). At the time the samples were taken, most likely by Ulski during hydrographic expeditions in 1858 to 1864 (Anistratenko et al. 2018), the nautical fathom (morskaya sazhen) measured 1.853 m, denoting a collection of depth of approximately 85 m. Finally, the shells of the type series closely resemble the material from the von Baer collection in terms of morphology and preservation (Fig. 2; compare also Anistratenko et al. 2019), substantiating the interpretation that they originally come from the same lot.
In order to fix the identity of Andrusovia dybowskii, we choose as lectotype a specimen from the lot containing four specimens (CNHM ZMKJ 50; Fig. 2a, b, e); the remaining three shells in that lot are paralectotypes (CNHM ZMKJ 51–53).
Additionally, several paratypes of other Andrusovia species here considered synonymous are found in MSU; the holotypes are however not traced. This concerns 5 paratypes of A. andrusovi (Lc-24600, Lc-24601, Lc-24604), 2 paratypes of A. brusinai (Lc-24598, Lc-24599) and 8 paratypes of Horatia marina (Lc-24613, Lc-24614).
Type locality. “Mare Caspium” (Caspian Sea) (Table 1, locality 26). The depth indicated on the collection labels (“I iz 46 sež. dub.”, meaning “collected from a depth of 85 meters”; see above) confines the type locality to the Middle or South Caspian Basin. Type locality of A. andrusovi: Caspian Sea off Cheleken Peninsula, Turkmenistan (locality 19); the paratypes studied herein come from a locality to the south of the type locality (locality 18). Type locality of A. brusinai: Eastern part of the middle Caspian Sea (locality 8); the paratypes derive from locality 22 in the South Caspian Basin. Type locality of H. marina: Northern part of the middle Caspian Sea (locality 2); the paratypes come from locality 22.
Other material. 33 specimens in the “Caspian Mollusca” collection of the CNHM (CNHM ZMKJ 49) and 61 specimens (ZB-M W.Dyb. 8, 26–28, 35, 70, 116) from unknown locations in the Caspian Sea (locality 26).
Description. Broad conical shell with up to three whorls; measuring up to 1.34 mm in height, 1.27 mm in width. Protoconch consists of c. 1.05–1.15 whorls measuring approximately 380–415 µm; surface bears distinct, densely malleate sculpture, occasionally accompanied by 3–4 spiral threads on initial half whorl; triangular portion reaching from lower suture at c. 0.5–0.8 whorls to upper suture at end of protoconch lacks malleate sculpture but bears irregular, bulgy growth rims; protoconch–teleoconch transition marked by strong growth rim. Teleoconch whorls moderately convex, typically weakly flattened and weakly stepped, separated by distinct suture. Spire height variable: last whorl attains c. 71–84% of total shell height. Umbilicus funnel-shaped, round, very narrow. Umbilicus may be surrounded by bulge in some specimens, which is occasionally more pronounced and forms distinct keel. Aperture broadly ovoid to near circular, strongly attached to base of last whorl, which sometimes results in weak concavity at parietal margin and slightly asymmetric shape. Peristome thin or sometimes slightly thickened; distinctly sinuate in lateral view, with protruding central part and indentations adapically and abapically. Fine prosocyrt growth lines cover shell. In a few specimens, faint irregular spiral grooves appear on last whorl.
Remarks. The previous concepts of A. dybowskii applied in the literature were based on a low-spired morphology. While the phrase “conoidea vel discoidea” (i.e. conical or disciform) in the original description comprises a great variety of shell shapes, Logvinenko & Starobogatov (1966) considered only disciform specimens to represent Andrusovia dybowskii. This led them to believe the genus belongs in Planorbidae, and they listed it as subgenus of Anisus and synonymised the species with Anisus eichwaldi (Clessin & W. Dybowski in W. Dybowski, 1887). Starobogatov (2000) revised this opinion and considered shells with depressed spire to represent A. dybowskii and classified Andrusovia in Horatiidae. Based on this concept, he introduced two more species based on variation of spire height: Andrusovia brusinai for high-spired forms and Andrusovia andrusovi for specimens with a spire height intermediate between A. brusinai and A. dybowskii (sensu Starobogatov 2000). He additionally classified Horatia marina Logvinenko & Starobogatov, 1969 in Andrusovia as well. He already noted the similarity of that species to his A. brusinai, but despite strong overlap in all measurements and ratios he still considered both species distinct.
The newly discovered type series demonstrates that the previous concepts of A. dybowskii applied by Logvinenko & Starobogatov (1966) and Starobogatov (2000) were misapplications: the type series contains only forms that are high-spired or slightly less so; no disciform specimens are found (which makes Brusina’s original description quite misleading). Comparing the available type material for all three species shows that they cannot be sufficiently separated. Specifically, A. brusinai and A. marina (Fig. 2g, h, y–aa, ad, ae), which partly co-occur in the same localities, are near identical to the type series of A. dybowskii.
The comparably low-spired morphology of Andrusovia andrusovi (Fig. 2 ae) is not found among the type series of Brusina and only few shells in the von Baer collection come close (Fig. 2x). Given the variation in spire height observed among the specimens of A. dybowskii, we consider A. andrusovi to range within its variability.
In addition to variation in spire height, some specimens (particularly the more slender ones) may bear a weak bulge (Fig. 2f, s, z) or a distinct keel (Fig. 2l, v, aa) surrounding the umbilicus. This trait variability is also seen in the type series. Given the overall high morphological variability of A. dybowskii and the variable expression of this trait, we consider it to range with intraspecific variation. If live material of this species could be collected, a molecular study might provide more insights about the systematic significance of this and other traits.
In summary, we consider all these morphologies to belong to a single polymorphic species, A. dybowskii, rendering A. andrusovi, A. brusinai and A. marina its junior subjective synonyms. This also makes the subgenus Horatia (Caspiohydrobia) Logvinenko & Starobogatov, 1969, with H. marina as type species, a junior subjective synonym of Andrusovia (see also Anistratenko et al. 2019).
Distribution. Endemic to the Caspian Sea, found in the Middle and South basins at depths between 34 and 311 m.
description: Published as part of Anistratenko, Vitaliy V., Neubauer, Thomas A., Anistratenko, Olga Yu., Kijashko, Pavel V. & Wesselingh, Frank P., 2021, A revision of the Pontocaspian gastropods of the subfamily Caspiinae (Caenogastropoda: Hydrobiidae), pp. 151-197 in Zootaxa 4933 (2) on pages 158-161, DOI: 10.11646/zootaxa.4933.2.1, http://zenodo.org/record/4550146