Clausocalanus Giesbrecht, 1888

Clausocalanus  is  one  of  the  most  widespread  and  abundant  genus  of  planktonic  calanoid copepods in the world oceans. It is distributed in both coastal and offshore waters, and over a broad  latitudinal  range  in  both  hemispheres. The  core  of  each  species  and population  is  generally located in the epipelagic zone, but the vertical distribution of most species can extend down to meso-  and bathypelagic zones. Clausocalanus species are smaller or only slightly larger than 1 mm in total length. The genus was thoroughly revised by Frost and Fleminger (1968). A previous ICES Identification leaflet for Plankton (No. 38; G. P. Farran, revised by W. Vervoort, 1951)  covered three of  the  13  described  species  of Clausocalanus.  This  new  leaflet  updates  the  previous two works, and presents taxonomic and ecological characteristics, along with results from molecular studies,  on all 13 Clausocalanus species revised by Frost and Fleminger (1968).