Abstract
Purpose: :
Teleost outer retina show marked retinomotor movements (RMM) and synaptic plasticity. In light-adaptation, cone photoreceptors are contracted, its pedicles invaded by spinules from horizontal cell (HC) dendrites, and the HC size body reduced. Darkness induces the opposite changes. Triploid fishes are widely used in aquaculture. These fishes usually exhibit reduced aggressiveness, which is thought to be the consequence of reduced sex steroid plasma levels and lower number of cells in the central nervous system. The aim of this work is to compare RMM between diploid and triploid fishes.
Methods: :
For this study, certified diploid and triploid turbots (Scophthalmus maximus) were used. Before sacrifice, fishes were light- and dark-adapted and their retinas processed for optical microscopy studies. Vertical semithin sections were analyzed and the HC body area and cone myoide length determined.
Results: :
Dark-adapted retinas of diploid turbots showed a significant increase of the cone myoide length and the HC body area with regard to light adapted retinas. Otherwise, the changes in the same RMM were scanty in retinas of triploid dark-adapted turbots compared to light adapted ones.
Conclusions: :
These results suggest that the decrease in retinal plasticity along with the reduction of sex steroid plasma levels and number of cells could be an explanation of the reduced aggressiveness of triploid fishes.
Keywords: retina • plasticity