Adacna

Species of the genus Adacna have thin and often translucent oval or oval-triangular shells, with flattened and sometimes hardly visible radial ribs. The valves gape at the anterior and posterior margins. The pallial line has a sinus, which is usually rather deep. The hinge may have no teeth, but sometimes reduced cardinal teeth can be present in one or both valves.{{sfn|Logvinenko|Starobogatov|1969|p=337}}{{sfn|Kijashko|2013|pp=361–362, 377–379}}

The siphons of Adacna are long and fused, with few papillae on their ends. The foot is short and compressed.{{sfn|Kijashko|2013|p=362}}

Members of the genus Monodacna have less gaping shells, with a shallower pallial sinus. Species of Hypanis differ by stronger developed sharp ribs. The extinct Apscheronia and Caspicardium have more protruding umbones and more convex shells.{{cite journal|last1=Nevesskaja|first1=L. A.|last2=Paramonova |first2=N. P. |last3=Popov |first3=S. V. |date=2001 |title=History of Lymnocardiinae (Bivalvia, Cardiidae) |journal=Paleontological Journal |volume=35, Suppl. 3|pages=147–217}}

Adacna fragilis inhabits fresh- and brackish-water lakes of the Danube Delta, estuaries (limans) of the north-western Black Sea and the Taganrog Bay of the Sea of Azov.{{cite book |last1=Scarlato |first1=O. A. |last2=Starobogatov |first2=Y. I. |date=1972 |chapter=Klass dvustvorchatyye mollyuski — Bivalvia |trans-chapter=Class bivalve molluscs – Bivalvia |title=Opredelitel' fauny Chernogo i Azovskogo morey|trans-title=Guide to the fauna of the Black Sea and the Sea of Azov |editor-last1=Mordukhai-Boltovskoy |editor-first1=F. D. |volume=3 |location=Kiev |publisher=Naukova Dumka |page=216 |language=ru}}{{cite journal |last1=Gogaladze |first1=A. |last2=Son |first2=M. O. |last3=Lattuada |first3=M. |last4=Anistratenko |first4=V. V. |last5=Syomin |first5=V. L. |last6=Pavel |first6=A. B. |last7=Popa |first7=O. P. |last8=Popa |first8=L. O. |last9=ter Poorten |first9=J. J. |last10=Biesmeijer |first10=J. C. |last11=Raes |first11=N. |last12=Wilke |first12=T. |last13=Sands |first13=A. F. |last14=Trichkova |first14=T. |last15=Hubenov |first15=Z. K. |last16=Vinarski |first16=M. V. |last17=Anistratenko |first17=O. Y. |last18=Alexenko |first18=T. L. |last19=Wesselingh |first19=F. P. |date=2021 |title=Decline of unique Pontocaspian biodiversity in the Black Sea Basin: A review |journal=Ecology and Evolution |volume=11 |issue=19 |pages=12923–12947 |url=https://onlinelibrary.wiley.com/doi/10.1002/ece3.8022 |doi=10.1002/ece3.8022 |doi-access=free|pmid=34646444 |pmc=8495785 |bibcode=2021EcoEv..1112923G |hdl=1887/3238855 |hdl-access=free }} Adacna laeviuscula, Adacna vitrea and Adacna minima live in the Caspian Sea.{{sfn|Kijashko|2013|pp=377–379}} A. vitrea and A. minima were also present in the Aral Sea, but these populations seem to have gone extinct by the end of the 1970s during the human-driven shrinkage and salinization of the lake.{{cite book|last1=Andreeva|first1=S. I.|last2=Andreev|first2=N. I.|date=2003|title=Evolyutsionnyye preobrazovaniya dvustvorchatykh mollyuskov Aral'skogo morya v usloviyakh ekologicheskogo krizisa|trans-title=The evolutionary transformations of bivalve mollusks of the Aral Sea in the conditions of an ecological crisis|location=Omsk|publisher=Omsk State Pedagogical University|isbn=5-8268-0672-9|pages=85–89|language=ru}} Furthermore, the Caspian A. vitrea has been introduced into the Tsimlyansk Reservoir of the Don River and into the Taganrog Bay.

Cockles of the genus Adacna live on silty, sandy and sandy-silty bottoms at depths from 0 to 60 m (0 to 200 ft) in waters with salinity of up to 14‰,{{cite book|last1=Akhvlediani|first1=E. G.|date=1966|chapter=Rod Adacna|trans-chapter=Genus Adacna|title=Spravochnik po ekologii morskikh dvustvorok|trans-title=Handbook of the ecology of marine bivalves|editor-last1=Davitashvili|editor-first1=L. S|editor-last2=Merklin|editor-first2=R. L|location=Moscow|publisher=Nauka|pages=178–182|language=ru}} although A. fragilis and A. vitrea have also been found in freshwater habitats. These bivalves are mobile filter feeders that usually fully burrow into the sediment and leave their siphons on the surface. They feed on suspended detritus and unicellular algae, but are also able to consume food particles on the sediment surface. In the absence of suspended food particles, the molluscs burrow into the sediment and stir it up with their siphons.

Species that lived in the Aral Sea (reported as A. vitrea minima) have separate sexes. Most of their juveniles appeared in July and grew up to 10 mm long during the summer. After the first year of their lives the growth rate slowed down. Their maximum life span was 4–5 years.

The extinct Adacna praeplicata and Adacna praepraeplicata occur in deposits of the Apsheronian Basin,{{cite book |last=Kolesnikov |first=V. P. |date=1950 |title=Akchagyl'skie i apsheronskie molliuski|trans-title=Akchagylian and Apsheronian molluscs|series=Paleontologija SSSR |volume=10, Chast' 3, Vyp. 12 |location=Moscow; Leningrad |publisher=Izdatel'stvo Akademii nauk SSSR |pages=207–208 |language=ru}}{{cite book |last=Popov |first=G. I. |date=1961 |title=Apsheronskiy yarus Turkmenii|trans-title=The Apsheronian stage of Turkmenia|location=Ashkhabad |publisher=Izdatel'stvo Akademii Nauk Turkmenskoy SSR |pages=272–276 |language=ru}} which existed on the territory of the modern Caspian Sea during the Pleistocene from 1,8 or 2,1 million to 880,000–750,000 years ago.{{cite journal|last1=Krijgsman|first1=W.|last2=Tesakov|first2=A.|last3=Yanina|first3=T.|last4=Lazarev|first4=S.|last5=Danukalova|first5=G.|last6=Van Baak|first6=C. G. C.|last7=Agustí|first7=J.|last8=Alçiçek|first8=M. C.|last9=Aliyeva|first9=E.|last10=Bista|first10=D.|last11=Bruch|first11=A.|last12=Büyükmeriç|first12=Y.|last13=Bukhsianidze|first13=M.|last14=Flecker|first14=R.|last15=Frolov|first15=P.|last16=Hoyle|first16=T. M.|last17=Jorissen|first17=E. L.|last18=Kirscher|first18=U.|last19=Koriche|first19=S. A.|last20=Kroonenberg|first20=S. B.|last21=Lordkipanidze|first21=D.|last22=Oms|first22=O.|last23=Rausch|first23=L.|last24=Singarayer|first24=J.|last25=Stoica|first25=M.|last26=van de Velde|first26=S.|last27=Titov|first27=V. V.|last28=Wesselingh|first28=F. P.|date=2019|title=Quaternary time scales for the Pontocaspian domain: Interbasinal connectivity and faunal evolution|url=https://www.sciencedirect.com/science/article/pii/S001282521830415X?via%3Dihub|journal=Earth-Science Reviews|volume=188|pages=1–40|doi=10.1016/j.earscirev.2018.10.013|doi-access=free}} The former species was described as being similar and related to the extant Hypanis plicata which was also found in the Apsheronian deposits and at the time was placed within Adacna.

Adacna yaninae was described from the Late Pleistocene deposits of the mostly dry Konya Basin in south-eastern Turkey, which was previously occupied by a large lake. The species has been classified as a member of Adacna due to its structure of the hinge, although its shell is more convex compared to its congeners and it has sharp ribs which are more similar to those of Hypanis.{{cite journal|last1=Büyükmeriç|first1=Y.|last2=Wesselingh|first2=F. P.|date=2019|title=New cockles (Bivalvia: Cardiidae: Lymnocardiinae) from Late Pleistocene Lake Karapınar (Turkey): Discovery of a Pontocaspian refuge?|url=https://www.sciencedirect.com/science/article/pii/S1040618215302561|journal=Quaternary International|volume=465|pages=37–45|doi=10.1016/j.quaint.2016.03.018|url-access=subscription}}

Fossilized shells of the extant A. laeviuscula and A. vitrea occur in deposits of the Caspian Sea Basin since its Khazarian stage,{{cite journal|last1=Yanina|first1=T. A.|last2=Semikolennykh|first2=D. V.|last3=Sorokin|first3=V. M.|date=2024|title=Biodiversity of Malacofauna in the Caspian–Manych–Pont System in the Last Interglacial Era|journal=Arid Ecosystems|volume=14|number=2|pages=244–258|doi=10.1134/S2079096124700148}} which began 125,000–80,000 years ago. A. laeviuscula has also been found in the Late Pleistocene deposits of the Manych Depression where a strait connecting the Caspian and the Azov-Black Sea basins has repeatedly formed in the past.{{cite journal|last1=Svitoch|first1=A. A.|last2=Yanina|first2=T. A.|last3=Antonova|first3=V. M.|last4=van der Plicht|first4=J.|date=2008|title=The Khvalynian fauna of the Manych Depression|journal=Doklady Earth Sciences|volume=421|number=6|pages=987–991|doi=10.1134/S1028334X08060287}} A. vitrea also occurred in the Black Sea Basin during its brackish-water Neoeuxinian stage when the Caspian waters flowed into the Black Sea through the Manych strait from 16,000 to 12,500 years ago.{{cite journal|last=Nevesskaja|first=L. A.|date=1963 |title=Opredelitel' dvustvorchatykh mollyuskov morskikh chetvertichnykh otlozheniy Chernomorskogo basseyna|trans-title=Key to bivalve molluscs of marine Quaternary sediments of the Black Sea basin |journal=Trudy Paleontologicheskogo Instituta |volume=96|pages=1–211|language=ru}}

A. minima has been recorded from 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.{{cite journal|last1=van de Velde|first1=S.|last2=Yanina|first2=T. A.|last3=Neubauer|first3=T. A.|last4=Wesselingh|first4=F. P.|date=2020|title=The Late Pleistocene mollusk fauna of Selitrennoye (Astrakhan province, Russia): A natural baseline for endemic Caspian Sea faunas|url=https://www.sciencedirect.com/science/article/pii/S0380133019300735|journal=Journal of Great Lakes Research|volume=46|issue=5|pages=1227–1239|doi=10.1016/j.jglr.2019.04.001}} This species also occurs in the Holocene deposits of the Aral Sea.{{cite journal|last1=Filippov|first1=A.|last2=Riedel |first2=F.|date=2009|title=The late Holocene mollusc fauna of the Aral Sea and its biogeographical and ecological interpretation|url=https://www.sciencedirect.com/science/article/pii/S0075951108000224|journal=Limnologica|volume=39|issue=1|pages=67–85|doi=10.1016/j.limno.2008.04.003}}

The genus Adacna was established by Karl Eichwald in 1838 and initially included four species, which he previously attributed to the genus Glycymeris: G. laeviuscula, G. vitrea, G. colorata and G. plicata.{{cite journal|last=Eichwald |first=E. |date=1838 |title=Faunae Caspii Maris primitiae |journal=Bulletin de la Société Impériale des Naturalistes de Moscou |volume=11 |number=2|pages=125–174|url=https://www.biodiversitylibrary.org/page/41342125}}{{sfn|Kijashko|2013|p=358}} A. laeviuscula has been designated as the type species of the genus by Vest (1875).{{cite journal|last=Vest |first=W. von. |date=1875 |title=Ueber die Genera Adacna, Monodacna und Didacna Eichwald und deren Stellung im System |journal=Jahrbücher der Deutschen Malakozoologischen Gesellschaft |volume=2 |pages=309–325|url=https://www.biodiversitylibrary.org/page/27002949|language=de}}{{cite book|last1=Kantor|first1=Y. I.|last2=Sysoev|first2=A. V.|date=2005|title=Catalogue of molluscs of Russia and adjacent countries|location=Moscow|publisher=KMK Scientific Press Ltd.|page=351|isbn=5-87317-191-2|language=ru}}

The taxonomy of the genera Adacna, Monodacna and Hypanis varied in different works. Zhadin (1952), for instance, treated Adacna and Monodacna as distinct genera, while Hypanis was considered to be a subgenus of the former.{{cite book |last=Zhadin |first=V. I. | date=1952 |title=Mollyuski presnykh i solonovatykh vod SSSR |trans-title=Molluscs of Fresh and Brackish Waters of the USSR |url=https://www.zin.ru/publications/fauna_keys/keys_46_zhadin_1952.pdf |series=Opredeliteli po faune SSSR, izdavayemyye Zoologicheskim institutom AN |volume=46 |location=Moscow–Leningrad |publisher=The USSR Academy of Sciences Press |pages=350–355 |language=ru |url-status=live |archive-url=https://web.archive.org/web/20241202230923/https://www.zin.ru/publications/fauna_keys/keys_46_zhadin_1952.pdf |archive-date=2 December 2024}} Logvinenko and Starobogatov (1969) found distinguishing the genera difficult and regarded Adacna and Monodacna as subgenera of Hypanis.{{sfn|Logvinenko|Starobogatov|1969|p=319}} Starobogatov et al. (2004) recognized Adacna as a separate genus, with Monodacna being its subgenus.{{cite book|last1=Starobogatov|first1=Y. I.|last2=Bogatov|first2=V. V.|last3=Prozorova|first3=L. A.|last4=Saenko|first4=E. M.|date=2004|chapter=Molluscs|title=Key to Freshwater Invertebrates of Russia and Adjacent Lands|editor-last1=Tsalolikhin|editor-first1=S. J.|volume=6. Molluscs, Polychaetes, Nemerteans|location=Saint-Petersburg|publisher=Nauka|pages=48–50|isbn=5-02-026204-8|language=ru}} Currently, all three genera are considered distinct, although molecular studies are necessary to confirm their validity.{{cite journal|last1=Wesselingh|first1=F. P.|last2=Neubauer|first2=T. A.|last3=Anistratenko|first3=V. V.|last4=Vinarski|first4=M.|last5=Yanina|first5=T.|last6=ter Poorten|first6=J. J.|last7=Kijashko|first7=P.|last8=Albrecht|first8=C.|last9=Anistratenko|first9=O. Y.|last10=D'Hont|first10=A.|last11=Frolov|first11=P.|last12=Gándara|first12=A. M.|last13=Gittenberger|first13=A.|last14=Gogaladze|first14=A.|last15=Karpinsky|first15=M.|last16=Lattuada|first16=M.|last17=Popa|first17=L.|last18=Sands|first18=A. F.|last19=van de Velde|first19=S.|last20=Vandendorpe|first20=J.|last21=Wilke|first21=T.|date=2019|title=Mollusc species from the Pontocaspian region – an expert opinion list|url=https://zookeys.pensoft.net/article/31365|journal=ZooKeys|issue=827|pages=31–124|doi=10.3897/zookeys.827.31365|doi-access=free|pmid=31114425 |pmc=6472301 |bibcode=2019ZooK..827...31W}}

Neoadacna is a genus described by Ali-Zade (1973) which included A. laeviuscula (as the type species), A. praeplicata as well as Hypanis plicata and Hypanis andrussowi, which were previously often included in Adacna.{{cite book|last=Ali-Zade|first=A. A.|date=1973|title=Apsheron Azerbaydzhana|trans-title=Apsheronian of Azerbaijan|location=Moscow|publisher=Nedra|pages=123–125|language=ru}} Nevesskaja et al. (2001) listed Neoadacna as a partial synonym of Hypanis and Adacna, while J. J. ter Poorten (2024) treated it as a synonym of the latter.{{cite book|last=ter Poorten|first=J. J.|date=2024|title=A taxonomic iconography of living Cardiidae|location=Harxheim|publisher=ConchBooks|isbn=978-3-948603-48-9|page=150}}

The following species are recognized:{{cite web|author=((MolluscaBase eds.)) |date=2024 |title=Adacna Eichwald, 1838 |url=https://molluscabase.org/aphia.php?p=taxdetails&id=381866 |website=MolluscaBase. |access-date=6 April 2025|url-status=live|archive-url=https://web.archive.org/web/20250303124813/https://www.molluscabase.org/aphia.php?p=taxdetails&id=381866 |archive-date=3 March 2025}}

• Adacna fragilis Milaschewitsch, 1908
• Adacna laeviuscula (Eichwald, 1829)
• Adacna minima Ostroumov, 1907
• Adacna vitrea (Eichwald, 1829)

• Adacna praeplicata V. P. Kolesnikov, 1950
• Adacna praepraeplicata G. I. Popov, 1961
• Adacna yaninae Büyükmeriç & Wesselingh, 2018

{{Reflist}}

• {{cite book|last=Kijashko|first=P. V.|date=2013|chapter=Mollyuski Kaspiyskogo morya|trans-chapter=Molluscs of the Caspian sea|title=Identification keys for fish and invertebrates of the Caspian Sea|editor-last1=Bogutskaya|editor-first1=N. G.|editor-last2=Kijashko|editor-first2=P. V.|editor-last3=Naseka|editor-first3=A. M.|editor-last4=Orlova|editor-first4=M. I.|volume=1. Fish and molluscs|location=St. Petersburg; Moscow|publisher=KMK Scientific Press Ltd.|pages=298–392|isbn=978-5-87317-932-9|language=ru}}
• {{cite book|last1=Logvinenko|first1=B. M.|last2=Starobogatov|first2=Y. I.|date=1969|chapter=Tip Mollyuski. Mollusca|trans-chapter=Phylum Molluscs. Mollusca|title=Atlas bespozvonochnykh Kaspiyskogo morya|trans-title=Atlas of the Invertebrates of the Caspian Sea|editor-last1=Birshteyn|editor-first1=Y. A.|editor-last2=Vinogradov|editor-first2=L. G.|editor-last3=Kondakov|editor-first3=N. N.|editor-last4=Kuhn|editor-first4=M. S.|editor-last5=Astakhova|editor-first5=T. V.|editor-last6=Romanova|editor-first6=N. N.|location=Moscow|publisher=Pishchevaya Promyshlennost|pages=308–385|language=ru}}

{{Taxonbar|from=Q11838747}}

Category:Cardiidae

Category:Bivalve genera

Category:Taxa named by Karl Eichwald

Category:Taxa described in 1838