Effect of Season and Environment on the Retinal Pigments of Two Fishes

Abstract

DARTNALL et al.¹ have shown that in the paired-pigment species Scardinius erythrophthalmus (visual pigments based on vitamin A₁ and on vitamin A₂) the retina is dominated by the vitamin A₂-based pigment in the winter and by the vitamin A₁-based pigment in the summer (in England at latitude 52° N.). The present report concerns a similar investigation on two species of fishes living in their natural habitats at lat. 25° N. in Florida, U.S A. One species, the poeciliid Balonesox belizanus Kner, was caught in an area of saline canals (average salinity about 10 parts per thousand), while the other, the cyprinid Notemigonus crysoleucas boscii Valenciennes, was caught in two environments separated by some 60 miles from each other. One of these, the ‘Cutler Rd. location’, was an area of drainage canals completely isolated from any other body of water throughout the period of the investigation (18 months)², whereas the other, the ‘Loop Rd. location’, was part of the canal, lake and swamp system covering most of south Florida and known as the ‘Everglades’. Both these environments were fresh water (average salinity below 1 part per thousand).