The Sternoptychidae (Pisces, Stomiatoidei) of the Amsterdam Mid North Atlantic Plankton Expedition 1980, with a note on specimens intermediate between Argyropelecus aculeatus Valenciennes, 1849 and A. olfersi (Cuvier, 1829)

The Sternoptychidae caught during a spring expedition in the Mid North Atlantic in 1980 are studied. Distribution patterns and data on abundance are recorded. It is proposed that Argyropelecus aculeatus and A. olfersi are two formae belonging to one species, the existing phenotypical differences being the result of adaptations to hydrographical circumstances. The intergrading zone of these formae is found at the surface at approximately 45°N and shifts to deeper water layers at lower latitudes.