Didacna baeri

Didacna baeri
Shell from the Holocene deposits of the Caspian Sea (Dagestan, Russia)
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Cardiida
Family: Cardiidae
Genus: Didacna
Species:
D. baeri
Binomial name
Didacna baeri
(Grimm, 1877)
Synonyms
  • Didacna alibajramliensis Gadzhiev, 1966

Didacna baeri is a brackish-water bivalve mollusc of the family Cardiidae, the cockles. It has a broadly-oval or oval-triangular, rather thick, whitish or cream shell, up to 40–50 mm (1.6–2.0 in) in length, with flattened and often brown ribs. The species is endemic to the Caspian Sea. It lives in the middle and southern parts of the lake at depths from 0 to 50–60 m (0 to 160–200 ft) and does not occur in desalinated areas. It is named after Baltic German scientist Karl Ernst von Baer.

Description

Didacna baeri has a broadly-oval or oval-triangular, rather thick, convex shell, with a weakly or moderately protruding umbo, 23–35 flattened radial ribs, which are often brown, and a distinct smooth posterior ridge.[1][2][3] The shell length is up to 40–50 mm (1.6–2.0 in).[2][3] The external coloration is whitish or cream, with thin pale yellowish green periostracum. The interior is white, often with a brown stain on the posterior margin.[3]

Differences from similar species

Didacna eichwaldi has a more protruding umbo and a sharp posterior ridge in juvenile individuals (sharp on the umbo in adults).[3][4]

Didacna longipes has a more equilateral, slightly thicker shell, with a sharper posterior ridge.[5]

Several fossil species are similar to D. baeri. Didacna surachanica usually has a lower and wider umbo. Didacna subcatillus differs by a less convex shell with a higher apical angle of the umbo. The shell of Didacna ovatocrassa is, on average, less elongated and less convex.[2]

Distribution and ecology

Didacna baeri is endemic to the Caspian Sea. It lives in the middle and southern parts of the lake at depths from 0 to 50 m (0 to 160 ft), rarely down to 60 m (200 ft).[6][7][8] The species does not occur in desalinated areas.[9]

The amphipod crustacean Cardiophilus baeri was first discovered in the mantle cavity of D. baeri.[10][11]

Fossil record

Didacna baeri is widespread in the Holocene (Neocaspian) deposits on the coasts of the middle and southern parts of the Caspian Sea[12] and rarely occurs in the Late Pleistocene (Upper Khvalynian) beds of the western coast of the lake. Nevesskaja (2007) hypothesized that the species descended from the Late Pleistocene (Lower Khvalynian) D. subcatillus.[2]

Taxonomy

Illustrations of Cardium baeri from Grimm's publication (1877)

The species was first described as Cardium Baeri by Oscar Andreevich Grimm in 1877. He named it after Baltic German scientist Karl Ernst von Baer.[13] The type locality of D. baeri is in the Caspian Sea off Turkmenistan (40°32'N, 52°23'E) at a depth of 37 m (121 ft).[3][14] Here, Grimm observed several hundred living individuals of this bivalve.[13] One of the specimens collected by him from the type locality is now kept in the Zoological Institute of the Russian Academy of Sciences and has been designated as the lectotype of the species by Logvinenko and Starobogatov (1967).[14][15]

Logvinenko and Starobogatov (1969) treated Didacna eichwaldi as a junior synonym of D. baeri.[6] This synonymy was followed in catalogues of extant molluscs of Russia[16][17] and by Kijashko (2013),[14] but was not accepted by some other authors such as Yanina (2005)[4] and Nevesskaja (2007).[2] Wesselingh et al. (2019) and subsequent authors treated these species as distinct due to differences in shell characteristics.[3][8][18]

Pravoslavlev (1939) described the variety transmittens from the Pleistocene deposits of the Lake Baskunchak and the Lower Volga near Chyorny Yar, Solyonoye Zaymishche and other places.[19] Svitoch (1967) treated it as a synonym of Didacna subpyramidata.[20] Nevesskaja (2007) listed Pravoslavlev's record of D. baeri in the synonymy of Didacna delenda.[2]

Gadzhiev (1968) described shells of D. baeri with a stronger protruding umbo from the Holocene deposits of the Baku Archipelago and Xanlar Island as the variety alata.[21] Yanina (2005) did not differentiate this variety from the "typical" D. baeri due to the presence of intermediate forms.[1] Additionally, the name of this taxon is invalid since it was introduced as variety after 1960. If the name becomes available it would be a junior homonym of Didacna alata.[22]

Didacna alibajramliensis is an extinct species described by Gadzhiev (1966) from Azerbaijan.[23] Nevesskaja (2007) regarded it as a tentative synonym of D. baeri.[2]

References

  1. ^ a b Yanina 2005, p. 243.
  2. ^ a b c d e f g Nevesskaja, L. A. (2007). "History of the genus Didacna (Bivalvia: Cardiidae)". Paleontological Journal. 41 (9): 861–949. Bibcode:2007PalJ...41..861N. doi:10.1134/s0031030107090018.
  3. ^ a b c d e f ter Poorten 2024, p. 158.
  4. ^ a b Yanina 2005, pp. 242–243.
  5. ^ ter Poorten 2024, p. 160.
  6. ^ a b Logvinenko, B. M.; Starobogatov, Y. I. (1969). "Tip Mollyuski. Mollusca" [Phylum Molluscs. Mollusca]. In Birshteyn, Y. A.; Vinogradov, L. G.; Kondakov, N. N.; Kuhn, M. S.; Astakhova, T. V.; Romanova, N. N. (eds.). Atlas bespozvonochnykh Kaspiyskogo morya [Atlas of the Invertebrates of the Caspian Sea] (in Russian). Moscow: Pishchevaya Promyshlennost. p. 324.
  7. ^ Kijashko 2013, p. 353.
  8. ^ a b Wesselingh, F. P.; Neubauer, T. A.; Anistratenko, V. V.; Vinarski, M.; Yanina, T.; ter Poorten, J. J.; Kijashko, P.; Albrecht, C.; Anistratenko, O. Y.; D'Hont, A.; Frolov, P.; Gándara, A. M.; Gittenberger, A.; Gogaladze, A.; Karpinsky, M.; Lattuada, M.; Popa, L.; Sands, A. F.; van de Velde, S.; Vandendorpe, J.; Wilke, T. (2019). "Mollusc species from the Pontocaspian region – an expert opinion list". ZooKeys (827): 31–124. Bibcode:2019ZooK..827...31W. doi:10.3897/zookeys.827.31365. PMC 6472301. PMID 31114425.
  9. ^ Zhadin, V. I. (1952). Mollyuski presnykh i solonovatykh vod SSSR [Molluscs of Fresh and Brackish Waters of the USSR] (PDF). Opredeliteli po faune SSSR, izdavayemyye Zoologicheskim institutom AN (in Russian). Vol. 46. Moscow–Leningrad: The USSR Academy of Sciences Press. p. 348. Archived (PDF) from the original on 2 December 2024.
  10. ^ Sars, G. O. (1896). "Crustacea Caspia. Contributions to the Knowledge of the Carcinological Fauna of the Caspian Sea. Amphipoda. Supplement". Bulletin de l'Académie Impériale des Sciences de St.-Pétersbourg. Série 5. 4 (5): 421–489.
  11. ^ Greze, I. I. (1985). Bokoplavy [Amphipods]. Fauna Ukrainy (in Russian). Vol. 26. Vyschije rakoobraznyje. Vypysk 5. Naukova Dumka. pp. 84–87.
  12. ^ Yanina 2005, p. 244.
  13. ^ a b Grimm, O. A. (1877). Kaspijskoe more i ego fauna [The Caspian Sea and its Fauna]. Trudy Aralo-Kaspiiskoi Ekspeditsii (in Russian). Vol. 2 (2). St. Petersburg: St. Petersburg Society of Naturalists. pp. 51–54.
  14. ^ a b c Kijashko 2013, p. 352.
  15. ^ Logvinenko, B. M.; Starobogatov, Y. I. (1967). "K izucheniyu vidovogo sostava fauny dvustvorchatykh mollyuskov tanatotsenozov podvodnogo sklona Azerbaydzhanskogo poberezh'ya Kaspiya" [On the study of species composition of the fauna of bivalves in tanatocoenoses of underwater slope of Azerbaijan coast of the Caspian Sea.]. In Kudritsky, D. M. (ed.). Opyt geologo-geomorfologicheskikh i gidrobiologicheskikh issledovaniy beregovoy zony morya [An experience of geologo-geomorphological and hydrobiological studies of coastal zone of the sea] (in Russian). Leningrad: Nauka. pp. 225–235.
  16. ^ Kantor, Y. I.; Sysoev, A. V. (2005). Catalogue of molluscs of Russia and adjacent countries (in Russian). Moscow: KMK Scientific Press Ltd. p. 353. ISBN 5-87317-191-2.
  17. ^ Vinarski, M. V.; Kantor, Y. I. (2016). Analytical catalogue of fresh and brackish water molluscs of Russia and adjacent countries. Moscow: A. N. Severtsov Institute of Ecology and Evolution of Russian Academy of Sciences. p. 71. ISBN 978-5-9908840-7-6.
  18. ^ Vinarski, M. V.; Kijashko, P. V.; Andreeva, S. I.; Sitnikova, T. Y.; Yanina, T. A. (2024). "Atlas and catalogue of the living mollusks of the Aral and Caspian Seas". Vita Malacologica. 23: 1–124. ISBN 978-3-948603-50-2.
  19. ^ Pravoslavlev, P. A. (1939). "Didacna Eichw. drevnekaspiyskikh otlozheniy Baskunchakskogo rayona" [Didacna Eichw. from ancient Caspian deposits of the Baskunchak region]. Uchenyye zapiski Leningradskogo gosudarstvennogo universiteta, seriya geologo-pochvennykh nauk (in Russian). 34 (7): 209–274.
  20. ^ Svitoch, A. A. (1967). Atlas-opredelitel' mollyuskov r. Didacna Eichwald iz chetvertichnyh otlozheniy Tsentral'nogo Prikaspiya [Atlas and Key to Molluscs of the Genus Didacna Eichwald from Quaternary Deposits of the Central Caspian Region] (in Russian). Moskva: Nedra. p. 28.
  21. ^ Gadzhiev, T. M. (1968). "Izmenchivost' Didacna baeri Grimm i nekotoryye novyye vidy Didacna novokaspiyskikh otlozheniy ostrovov Bakinskogo arkhipelaga" [Variability of Didacna baeri Grimm and some new species of Didacna of the Neocaspian deposits of the islands of the Baku archipelago]. Paleontologicheskiy sbornik (in Russian). 5 (1): 75–85.
  22. ^ MolluscaBase eds. (2021). "Didacna baeri var. alata Gadzhiev, 1968". MolluscaBase. Archived from the original on 24 February 2025. Retrieved 25 February 2025.
  23. ^ Gadzhiev, T. M. (1966). "Novaya fauna didakn iz drevnekaspiyskikh terras (M. Kharami)" [A new Didacna fauna from ancient Caspian terraces (Lesser Harami)]. Doklady Akademii Nauk Azerbaydzhanskoy SSR (in Russian). 22 (5): 35–39.

Cited texts

  • Kijashko, P. V. (2013). "Mollyuski Kaspiyskogo morya" [Molluscs of the Caspian sea]. In Bogutskaya, N. G.; Kijashko, P. V.; Naseka, A. M.; Orlova, M. I. (eds.). Identification keys for fish and invertebrates of the Caspian Sea (in Russian). Vol. 1. Fish and molluscs. St. Petersburg; Moscow: KMK Scientific Press Ltd. pp. 298–392. ISBN 978-5-87317-932-9.
  • ter Poorten, J. J. (2024). A taxonomic iconography of living Cardiidae. Harxheim: ConchBooks. ISBN 978-3-948603-48-9.
  • Yanina, Т. А. (2005). Didakny Ponto-Kaspiya [Didacnas of the Ponto-Caspian Region] (in Russian). Smolensk: Majenta. ISBN 5-98156-024-X.
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