Classification, diversity and biology of whalefishes and relatives

Whalefishes of the family Cetomimidae are among the deepest dwelling of deepsea fishes, with most species living in the bathypelagic area of the water column between 1.5 km and 3.5 km below the surface.

Research Fellow Dr John Paxton

Whalefishes of the family Cetomimidae are among the deepest dwelling of deepsea fishes, with most species living in the bathypelagic area of the water column between 1.5 km and 3.5 km below the surface. Whalefishes are so named not for their size (the largest is only 40 cm long and most of the 35 species do not exceed 20 cm), but for their shape - a large head, exceptionally large mouth, and fins placed far back on the body.

Living at depths of perpetual darkness, their eyes are reduced and a greatly enlarged lateral line provides information about the movements of predators and prey. Many questions remain about their biology. We do know that they eat mainly crustaceans, and that the only males so far found, at 3-5 cm length, are much smaller than mature females. Whalefish larvae of this family have never been found.

Current research projects on whalefishes include:

• revision of the genus Gyrinomimus with description of eight new species
• description of a new species of Cetomimus with a key to known species with T. Trnski
• DNA sequences and evolutionary relationships of whalefishes and related families with M. Miya of Chiba Museum, Japan and G.D. Johnson of the Smithsonian Institution.
• Osteology and evolutionary relationships with G.D. Johnson
• Gonad morphology and reproductive biology with H.G. Moser