Development of the sensory organs in the greenback flounder, Rhombosolea tapirina

Plastic resin histology and scanning electron microscopy were used to examine the development of the sense organs in greenback flounder from day 1 after hatching to early stage juveniles. A functional cone retina was present at the time of first feeding. Twin cones and rods developed later. There were two pairs of superficial neuromasts on the head of 1-day-old fish, with rapid proliferation of superficial neuromasts on the head and trunk thereafter. Lateral line canals first appeared on the head late in larval development, but trunk canals were still not present in early stage juveniles. The labyrinth initially contained 2 otolith organs with a full compliment of labyrinth organs present in late stage larvae. The olfactory organs were superficial cups of ciliated sensory epithelium in 1-day-old fish. These gradually sank into the rostral dermis, becoming enclosed except for anterior and posterior openings (nares) in juvenile fish. Metamorphosis, which involves migration of the left eye to the right side, and a change in posture of 90°, has implication for central processing of sensory information.