Oithona nana

Taxon-Order: 
Cyclopoida

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Distribution: 
Pacific, Atlantic and Indian Oceans in warmer waters; Mediterranean and Red Seas.
Habitat: 
Neritic, epipelagic.
Size: 
Females 0.4-0.6 mm; Males 0.4-0.6 mm Total Length
Diet: 
Probably carnivorous, feeding on motile phytoplankton and microzooplankton.
Predators: 
Predatory zooplankton, fish.
Useful Facts or Characters: 

In the female the 1st antennae reach to the end of the 3rd prosome segment.  The genital segment is nearly the same length as the next two segments combined.  In the male the 1st antennae are modified to form grasping structures.

Natural History: 

Shows strong positive phototaxis.

References: 

http://www.marinespecies.org/copepoda/aphia.php?p=taxdetails&id=106651

http://www.obs-vlfr.fr/~gaspari/copepods_guide/oitho_nana_fem.htm

http://copepodes.obs-banyuls.fr/en/fichesp.php?sp=1790

Nishida, S. (1985) Taxonomy and distribution of the family Oithonidae (Copepoda, Cyclopoida) in the Pacific and Indian Oceans. Bulletin of the Ocean Research Institute of the University of Tokyo 20: 1-167.