Didacna longipes

Didacna longipes
Illustrations of Cardium longipes from Oscar Grimm's publication (1877)
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Cardiida
Family: Cardiidae
Genus: Didacna
Species:
D. longipes
Binomial name
Didacna longipes
(Grimm, 1877)

Didacna longipes is a brackish-water bivalve mollusc of the family Cardiidae, the cockles. It has an oval, rather thick, cream shell, up to 25 mm (0.98 in) in length, with a weakly protruding umbo and flattened ribs, which are often highlighted only by color. The species is endemic to the Caspian Sea. It lives in the southern and middle parts of the lake and in the southern portion of the Northern Caspian at depths from 0 to 30 m (0 to 98 ft).

Description

Didacna longipes has an oval, almost equilateral, rather thick, moderately convex shell, with a weakly protruding umbo, 26–33[1] flattened radial ribs, which are often highlighted only by color, and a distinct smooth or sharp posterior ridge, which often becomes almost invisible near the ventral margin.[2][3][4] The shell length is up to 25 mm (0.98 in), the height is up to 23 mm (0.91 in), and the convexity is up to 16 mm (0.63 in).[2] The external coloration is cream. The interior is white.[4]

Differences from similar species

Didacna baeri has a less equilateral, slightly thinner shell, with a smoother posterior ridge.[5]

The juveniles of Didacna barbotdemarnii differ from those of D. longipes by having thinner shells, with less pronounced growth lines, less ribs, a somewhat wider umbo, sharper posterior ridge, narrower anterior margin and a more elongated posterior margin.[3]

Distribution and ecology

Didacna longipes is endemic to the Caspian Sea. It lives in the southern and middle parts of the lake and in the southern portion of the Northern Caspian at depths from 0 to 30 m (0 to 98 ft). The species avoids areas with salinity of less than 10‰ and often co-occurs with D. barbotdemarnii.[3][6]

The species first appeared in the Caspian Sea during the Holocene.[7]

Taxonomy

The species was first described as Cardium longipes by Oscar Andreevich Grimm in 1877.[8] The type locality is in the Caspian Sea off Azerbaijan (40°39'N, 50°16'E) at a depth of 11 m (36 ft).[4][9] The specimens collected by Grimm from this locality are kept in the Zoological Institute of the Russian Academy of Sciences (ZIN) and one of them has been designated as the lectotype of D. longipes by Logvinenko and Starobogatov (1967).[10][11]

The taxonomic status of D. longipes was uncertain in the past.[11] For instance, it has been proposed that the species could be a "deformed form" of D. baeri.[1] Logvinenko and Starobogatov (1967) have confirmed that D. longipes is a distinct and valid species, but also noted that Grimm's specimens from the ZIN differ somewhat from the original illustrations of the species.[11]

Nevesskaja (2007) believed that D. longipes could not be clearly identified from the existing descriptions and described the new species, Didacna carinata. According to the description it is similar to D. barbotdemarnii and differs by a more pronounced posterior ridge, more protruding umbo, more convex shell and less developed cardinal teeth. Among the figures of D. carinata were Grimm's illustrations of D. longipes, although D. longipes was not explicitly treated as a synonym of the new species. The holotype of D. carinata is stored in the Paleontological Institute of the Russian Academy of Sciences.[12][13] Kijashko (2013) have concluded that D. longipes is a valid species, while the taxonomic status of D. carinata is uncertain and it has been treated as a tentative synonym of both D. longipes and D. barbotdemarnii.[13][14]

References

  1. ^ a b 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. pp. 349–350. Archived (PDF) from the original on 2 December 2024.
  2. ^ a b Logvinenko & Starobogatov 1969, p. 326.
  3. ^ a b c Kijashko 2013, p. 355.
  4. ^ a b c ter Poorten 2024, p. 160.
  5. ^ ter Poorten 2024, p. 158.
  6. ^ Logvinenko & Starobogatov 1969, pp. 326–327.
  7. ^ 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.
  8. ^ 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. 54–56.
  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. p. 71. ISBN 978-5-9908840-7-6.
  10. ^ Kijashko 2013, p. 354.
  11. ^ a b c 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.
  12. ^ 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.
  13. ^ a b Kijashko 2013, pp. 354–355.
  14. ^ ter Poorten 2024, pp. 160, 162.

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.
  • 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. pp. 308–385.
  • ter Poorten, J. J. (2024). A taxonomic iconography of living Cardiidae. Harxheim: ConchBooks. ISBN 978-3-948603-48-9.
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