Ocular morphology of the sweep Scorpis lineolatus and the spotty Notolabrus celidotus (Pisces: Teleostei) grown in low intensity light.

Adults of two species of teleost fishes, the New Zealand sweep (Scorpis lineolatus) and the spotty (Notolabrus [formerly Pseudolabrus] celidotus), were recovered from dark, sealed sea water storage tanks after an extended period of residence (physical constraints meant that fish could only have entered the system as larvae or small juveniles). Individuals of both species had proportionately larger eyes than normal fishes of similar body size. Age estimation, based on unvalidated annual increments in otoliths indicated that fishes from the water tanks were all older (i.e. slower-growing) than normal fishes of similar size. This suggests that the increase in relative eye size in tank fishes may have been the result of maintenance of ocular growth, in the face of reduced rates of somatic growth, and raises the question as to whether eye growth in fishes generally, is a temporal function. In addition to ocular enlargement, sweeps from the water tanks also showed reduced densities of cones, rods, ganglion cells and, in some cases bipolar cells compared to normal fishes of similar body size. Cone, rod and bipolar cell densities of tank fishes were not different when compared with normal fishes of similar eye size; however, ganglion cell numbers were still lower than in normal fishes. This suggests that changes in cone, rod and bipolar cell densities in tank fishes resulted from the normal changes that occur with ocular growth, whereas low ganglion cell densities were a direct result of the abnormal photic environment. In contrast to the sweeps, most of the spotties from the water tanks did not show differences in retinal cell densities relative to normal fishes.(ABSTRACT TRUNCATED AT 250 WORDS)