{{Short description|Species of crustacean}} {{Speciesbox | image = | genus = Calanus | species = euxinus | authority = Hulsemann, 1991 }}
'''''Calanus euxinus''''' is a copepod ubiquitous to the Black Sea and the Marmara Sea<ref name=":0">{{Cite journal |last=Hulsemann |first=K |date=1991 |title=Calanus euxinus, new name, a replacement name for Calanus ponticus Karavaev, 1894 (Copepoda: Calanoida). |journal=Proc Biol Soc Wash |issue=104 |pages=620–621}}</ref> and a main source of prey for small and juvenile fish as the largest part of the zooplankton biomass.<ref name=":1">{{Cite journal |last=Svetlichny |first=LS |last2=Yuneva |first2=TV |last3=Hubareva |first3=ES |last4=Schepkina |first4=AM |date=2009 |title=Development of Calanus euxinus during spring cold homothermy in the Black Sea |journal=Mar Ecol Prog Ser |issue=374 |pages=199–213}}</ref>
''Calanus euxinus'' was misidentified originally as a variation of ''Calanus finmarchicus'' and ''Calanus helgolandicus'', until being labeled as its own species.<ref>{{Cite journal |last=Karavaev |first=V |date=1894 |title=Contributions to the Crustacean pelagic fauna of the Black Sea. Kiev Universitet. Obshestvo estestvoispitatelei |journal=Zapiski |issue=13 |pages=35–61}}</ref><ref name=":0" /> ''Calanus euxinus'' are considerably larger than Mediterranean species, like ''Calanus helgolandicus'', with a larger lipid reserve.<ref name=":2">{{Cite journal |last=Fleminger |first=A |last2=Hulsemann |first2=K |date=1987 |title=Geographical variation in Calanus helgolandicus s.l. (Copepoda, Calanoida) and evidence of recent speciation of the Black Sea population |journal=Biol Oceanogr |issue=5 |pages=43–81}}</ref><ref name=":1" />
Previous origin hypotheses, assumed the Black Sea ''Calanus'' to be derived from a population of ''Calanus helgolandicus'' in the Mediterranean,<ref name=":2" /> but more recent phenetic research points to earlier population divergences from the Boreal derived ''Calanus''.<ref>{{Cite journal |last=Zaitsev |first=YuP |date=2006 |title=An introduction on the Black Sea ecology |journal=Aven, Odessa}}</ref><ref>{{Cite journal |last=Papadopoulos |first=LN |last2=Peijnenburg |first2=KTCA |last3=Luttikhuizen |first3=PC |date=2005 |title=Phylogeography of the calanoid copepods Calanus helgolandicus and C. euxinus suggests Pleistocene divergences between Atlantic, Mediterranean, and Black Sea populations |journal=Mar Biol |issue=147 |pages=1353–1365}}</ref>
== Diel vertical migration == Like other copepods, ''Calanus euxinus'' follow typical vertical migration patterns, hunting at night at the surface and sinking near the oxygen minimum zone during the daytime.<ref name=":1" /> There is no significant difference in seasonal total abundance in deep-water,<ref>{{Cite journal |last=Sazhina |first=LI |date=1987 |title=Reproduction, growth, productivity of marine Copepoda |journal=Naukova Dumka, Kiev}}</ref> as the final copopodite stage staggers entering their diapause state from June to September<ref name=":3">{{Cite journal |last=Besiktepe |first=S |date=2001 |title=Diel vertical distribution and herbivory of copepods in the south-eastern part of the Black Sea |journal=J Mar Syst |issue=28 |pages=281–301}}</ref> and rest along the lower limit of the oxygenated layer of the water column.<ref>{{Cite journal |last=Vinogradov |first=M.Ye. |last2=Musayeva |first2=E.I. |last3=Semeneva |first3=T.N. |date=1990 |title=Factor determining the position of the lower layer of mesoplankton concentration in the Black Sea |journal=Oceanology |issue=30 |pages=217–224}}</ref><ref>{{Cite journal |last=Besiktepe |first=S |last2=Telli |first2=M |date=2004 |title=Egg production and growth rates of Calanus euxinus (Copepoda) in the Black Sea |journal=J Plankton Res |issue=26 |pages=571–578}}</ref>
Diel vertical migrations can span 80-180 meters in depth.<ref>{{Cite journal |last=Vinogradov |first=ME |last2=Arashkevich |first2=EG |last3=Ilchenko |first3=SV |date=1992 |title=The ecology of the Calanus ponticus population in the deeper layer of its concentration in the Black Sea |journal=J Plankton Res |issue=14 |pages=447–458}}</ref><ref name=":3" /> The bottom of the migration tends to remain consistent temperatures year-round, with water column temperature gradients becoming steep during summer and autumn stratification.<ref>{{Cite journal |last=Besiktepe |first=S |last2=Kideys |first2=AE |last3=Unsal |first3=M |date=1998 |title=In situ grazing pressure and diel vertical migration of female Calanus euxinus in the Black Sea |journal=Hydrobiologia |issue=363 |pages=323–332}}</ref><ref>{{Cite journal |last=Besiktepe |first=S |last2=Svetlichny |first2=L |last3=Yuneva |first3=T |last4=Romanova |first4=Z |last5=Shulman |first5=G |date=2005 |title=Diurnal gut pigment rhythm and metabolic rate of Calanus euxinus in the Black Sea |journal=Mar Biol |issue=146 |pages=1189-1198}}</ref> In the Black Sea, there is very little change in salinity, staying brackish throughout the water column, while the Marmara Sea experiences consistently steep salinity gradients.<ref name=":4">{{Cite journal |last=Svetlichny |last2=Leonid |last3=Hubareva |last4=Elena |last5=Isinibilir |last6=Melek |last7=Kideys |last8=Ahmet |last9=Belmonte |last10=Genuario |last11=Giangrande |last12=Elisa |date=2010 |title=Salinity tolerance of Calanus euxinus in the Black and Marmara Seas |journal=Marine Ecology Progress Series |issue=404}}</ref>
== Salinity adaptations == The difference in salinity gradients between the Black and Marmara Seas leads to limitations on the development of ''Calanus euxinus''. There are noticeable examples of the Black Sea and estuarine copepods displaying decreases in swimming activity, total locomotion, body length, and development time.<ref name=":4" /><ref>{{Cite journal |last=Svetlichny |first=LS |last2=Hubareva |first2=ES |last3=Erkan |first3=F |last4=Gucu |first4=AG |date=2000 |title=Physiological and behavioral aspects of Calanus euxinus females (Copepoda, Calanoida) during vertical migration |journal=Mar Biol |issue=137 |pages=963–971}}</ref><ref>{{Cite journal |last=Seuront |first=L |date=2006 |title=Effect of salinity on the swimming behaviour of the estuarine calanoid copepod Eurytemora affinis |journal=J Plankton Res |issue=28 |pages=805–813}}</ref> Overall, the Marmara Sea population of ''Calanus euxinus'' tend to develop to adult stages faster than the Black Sea, which leads to a reduction of large lipid storage, smaller bodies, and significantly higher respiration rates due to the development under high salinity conditions.<ref name=":4" /><ref>{{Cite journal |last=Svetlichny |first=LS |last2=Kideys |first2=AE |last3=Hubareva |first3=ES |last4=Besiktepe |first4=S |last5=Isinibilir |first5=M |date=2006 |title=Development and lipid storage in Calanus euxinus from the Black and Marmara seas: variabilities due to habitat conditions |journal=J Mar Syst |issue=59 |pages=52–62}}</ref><ref>{{Cite journal |last=Isinibilir |first=M |last2=Svetlichny |first2=LS |last3=Hubareva |first3=ES |last4=Ustun |first4=F |last5=Yilmaz |first5=NI |last6=Kideys |first6=AE |last7=Bat |first7=L |date=2009 |title=Population dynamics and morphological variability of Calanus euxinus in the Black and Marmara Seas |journal=Ital J Zool |issue=76 |pages=403–414}}</ref>
== References == {{Reflist}}
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Category:Calanoida