Adacna minima

Adacna minima
Fossil shells from the Late Pleistocene deposits of the lower Volga (near Selitrennoye)
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Cardiida
Family: Cardiidae
Genus: Adacna
Species:
A. minima
Binomial name
Adacna minima
Ostroumov, 1907

Adacna minima is a brackish-water cockle, a bivalve mollusc of the family Cardiidae. It has a suboval or subrhomboidal, thin and semitranslucent whitish shell, up to 16–20 mm (0.63–0.79 in) in length, with flattened and sometimes almost invisible ribs. The species is native to the Caspian Sea where it lives at depths from 0 to 35 m (0 to 115 ft) in its central and southern parts and rarely occurs in the eastern portion of the Northern Caspian. It was previously distributed throughout the entire Aral Sea where it became locally extinct after 1977 as the lake was shrinking and became more saline due to human activity.

Description

Adacna minima has a suboval or subrhomboidal, thin, compressed, semitranslucent whitish shell, with flattened and sometimes almost invisible radial ribs and a very shallow, wide pallial sinus.[1][2][3] The shell length is up to 16–20 mm (0.63–0.79 in).[3] The valves are moderately gaping posteriorly.[2] The hinge has a relatively well developed cardinal tooth in the left valve[3] and a reduced cardinal tooth in the right valve.[1][2]

Distribution and ecology

Adacna minima is native to the Caspian Sea where it lives at depths from 0 to 35 m (0 to 115 ft) in its central and southern parts and rarely occurs in the eastern portion of the Northern Caspian.[1][2]

Additionally, the species used to be distributed throughout the entire Aral Sea where it lived at depths from 0 to over 10–12 m (0 to 33–39 ft).[4] By 1965, as the lake began to shrink and become more saline due to human activity, most specimens of A. minima had deformed shells.[5] It was last seen in the Aral Sea in 1977 and has not been recorded there in the following years.[6]

Fossil record

Adacna minima is abundant in the Late Pleistocene deposits of the lower Volga River corresponding to the Hyrcanian stage of the Caspian Sea which began 107,000 ± 7,000 years ago.[7] It also occurs in the Holocene deposits of the Aral Sea.[8]

Taxonomy

The species was first described from the Northern Caspian Sea and the Aral Sea by a Russian zoologist Alexey Alexandrovich Ostroumov in 1907.[9] The type specimens have not been traced.[10]

Zhadin (1952) did not list A. minima as a distinct species, but used its name for a variety of Adacna vitrea (A. vitrea var. minima) and indicated that it lives along the northern shore of the Caspian Sea and in the Aral Sea.[11] Later authors have treated A. vitrea and A. minima as distinct species both of which inhabit the Caspian Sea and were previously present in the Aral Sea. The Northern Caspian form of A. vitrea from desalinated areas near the Volga and the Ural rivers is now known under the name A. vitrea glabra.[1][12][13]

Logvinenko and Starobogatov (1967) described the Caspian population of A. minima as the subspecies A. minima ostroumovi, with the holotype being collected near the Ogurchinskiy Island.[14] Later, Starobogatov (1974) recognized two subspecies of A. minima in the Aral Sea: A. minima minima and the newly described A. minima sidorovi. The former occurred at depths of over 10–12 m (33–39 ft), while the latter lived in the coastal zone at depths of up to 10 m (33 ft) and differs by more visible ribs (the lectotype[15] was found on the western coast of the Aral Sea near the Kara-Kibir well).[4] Andreeva and Andreev (2003) regarded A. minima sidorovi as a distinct species (as Hypanis sidorovi) and believed that it could be distinguished from A. minima and A. vitrea by the shape of the ligament.[16] The type specimens of A. minima ostroumovi and A. minima sidorovi are kept in the Zoological Institute of the Russian Academy of Sciences.[17] Wesselingh et al. (2019) questioned the validity of these subspecies and synonymized them with A. minima,[12] while Vinarski et al. (2024) listed them as valid.[13] Molecular studies of these taxa would be difficult as the species is likely extinct in the Aral Sea.[12]

References

  1. ^ a b c d 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. 338.
  2. ^ a b c d 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. p. 378. ISBN 978-5-87317-932-9.
  3. ^ a b c ter Poorten, J. J. (2024). A taxonomic iconography of living Cardiidae. Harxheim: ConchBooks. p. 150. ISBN 978-3-948603-48-9.
  4. ^ a b Starobogatov, Y. I. (1974). "Klass Dvustvorchatyye mollyuski, Bivalvia" [Class Bivalve Molluscs, Bivalvia]. In Mordukhai-Boltovskoi, F. D.; Kondakov, N. N.; Markova, Y. L.; Romanova, N. N.; Yablonskaya, Y. A. (eds.). Atlas bespozvonochnykh Aral'skogo morya [Atlas of the Invertebrates of the Aral Sea] (in Russian). Moscow: Pishchevaya Promyshlennost. pp. 245–247.
  5. ^ Andreeva & Andreev 2003, pp. 91.
  6. ^ Andreeva & Andreev 2003, pp. 88–89.
  7. ^ van de Velde, S.; Yanina, T. A.; Neubauer, T. A.; Wesselingh, F. P. (2020). "The Late Pleistocene mollusk fauna of Selitrennoye (Astrakhan province, Russia): A natural baseline for endemic Caspian Sea faunas". Journal of Great Lakes Research. 46 (5): 1227–1239. doi:10.1016/j.jglr.2019.04.001.
  8. ^ Filippov, A.; Riedel, F. (2009). "The late Holocene mollusc fauna of the Aral Sea and its biogeographical and ecological interpretation". Limnologica. 39 (1): 67–85. doi:10.1016/j.limno.2008.04.003.
  9. ^ Ostroumov, A. A. (1907). "O mollyuskakh Aralskago morya" [On the molluscs of the Aral Sea]. Izvestiya Turkestanskogo otdeleniya Russkogo Geograficheskogo obshchestva (in Russian). 4 (7): 20–26.
  10. ^ Vinarski & Kantor 2016, p. 64.
  11. ^ 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. 353. Archived (PDF) from the original on 2 December 2024.
  12. ^ a b c 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.
  13. ^ a b 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.
  14. ^ 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.
  15. ^ Vinarski & Kantor 2016, p. 74.
  16. ^ Andreeva & Andreev 2003, pp. 86.
  17. ^ Vinarski & Kantor 2016, p. 64, 74.

Cited texts

  • Andreeva, S. I.; Andreev, N. I. (2003). Evolyutsionnyye preobrazovaniya dvustvorchatykh mollyuskov Aral'skogo morya v usloviyakh ekologicheskogo krizisa [The evolutionary transformations of bivalve mollusks of the Aral Sea in the conditions of an ecological crisis] (in Russian). Omsk: Omsk State Pedagogical University. ISBN 5-8268-0672-9.
  • 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. ISBN 978-5-9908840-7-6.
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