Bathykorus bouilloni

…is a species of Aeginid hydrozoan that is the sole member of the genus Bathykorus. Bathykorus bouilloni is native to the Arctic Ocean and is most common around Greenland and northern Canada. B. bouilloni is a deep water species and is found in waters ranging from 800 to 2,500 m (2,600 to 8,200 ft). Because of this ‘extreme’ habitat it is difficult to study and much is still unknown about its biology and ecology.


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Image: Kevin Raskoff

Genus: Crossota

…a genus of rhopalonematid hydrozoans that are widespread throughout all oceans. Unlike some other hydrozoans (and like trachymedusae) members of Crossota do not have a sessile larval stage. Instead they spend their entire lives in the water column as “plankton”. Once they reach adulthood as medusae they will feed on zooplankton which are dispatched via nematocysts.



Image: Kevin Raskoff, NOAA Photo Library


Aegina citrea

Sometimes known as the “Golf Tee Medusa” Aegina citrea is a species of Aeginid hydrozoan that boasts a cosmopolitan distribution throughout the Atlantic and Pacific oceans. Like other many other cnidarians Aegina citrea is a planktonic ‘predator’ feeding on small invertebrates and other organisms. 


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Images: ©Robert Lee

Botrynema ellinorae

…is a species of Halicreatid hydrozoan which is typically encountered in the mesopelagic and bathypelagic zones of the Arctic ocean at depths of around (400 to 1,400 m). However it is also been recorded in subarctic regions of the Atlantic Ocean as well. B. ellinorae is poorly researched and as such its diet and ecology is not known, it is thought that B. ellinorae lacks a polyp stage and is holoplanktonic.


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Image: Kevin Raskoff