Monday, January 18, 2016

Marine Ostracods

Ostracods are often called seed shrimp which is in reference to their body shape. Their bodies are flattened from side to side and protected by a mussel-like, chitinous or calcareous valve or "shell". The hinge of the two valves is in the upper region of the body. 

Planktonic ostracods are thought to play an important role in the cycling of organic carbon below the thermocline and they are also sensitive to water temperature and salinity changes, making them potential indicators of climate change.

Some 40,000 species have been described but the majority of them is long extinct and known only through the fossil record. Species numbers vary greatly in the literature and the true diversity of extant ostracods is - as in many other groups - unknown. There are more than 200 described species of marine planktonic ostracods, many of which (especially conspecific species) can be identified only by microscopic examination and dissection of fragile morphological characters. 

On top of the problems of morphological identifications there is a dramatic lack of taxonomic expertise for the group -  only two or three active researchers currently have sufficient expertise for species identification and description .Given all these problems, DNA Barcodes seemed particularly useful and necessary. 

An international group of colleagues now adds DNA Barcodes of 78 species of marine planktonic ostracods to the global reference library, including two novel species, and 51 species for which DNA Barcodes have not been previously published. Specimens were collected back in 2006 to 2008 from the Atlantic, Indian, and Southern Oceans, Greenland Sea and Gulf of Alaska. Samples were collected from surface to 5,000 m using various collection devices. This number might not sound very impressive and large but given the difficulties to obtain these species it is certainly a great accomplishment.

Not surprisingly they researchers concluded:

Based on taxonomically and geographically extensive sampling and analysis (albeit with small sample sizes), the COI barcode region was shown to be a valuable character for discrimination, recognition, identification, and discovery of species of marine planktonic ostracods.

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