The Eyes of Larval Fish
Fish may be oviparous or live-bearing. The incubation time for the eggs is usually short (except in some species like the salmonids). The eggs float in the water or are attached to the bottom. The larvae of many species of teleost are small, transparent and delicate and lack many of the anatomical features found in the adult. The gut and kidney are relatively simple, the blood is colourless and acellular, the gills are without filaments, the skin lacks scales and pigment and some of the median fins are absent. These structures develop later. In particular, the larvae often undergo a metamorphosis when the blood turns pink and the scales form, the larvae taking on the adult form. In flatfish this metamorphosis is more elaborate, since one eye migrates and the fish come to lie permanently on one or other side. As an example of such development some stages of growth in herring and plaice are shown in Fig. 1.
KeywordsLarval Fish Outer Nuclear Layer Nile Perch Visual Cell Visual Threshold
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