Comparative Retina Stratification in Embryos, Larvae and Adults of Alburnus chalcoides

The present investigation considered retina structure in embryos, larvae and adult Alburnus chalcoides. Histological samples of retina were provided from adult fish, different stages of embryonic and larval development. Eye primordia formed from ectoderm at 16 hours after fertilization (16hAF) and then developed to eye cups. Initial eye cup which contained undifferentiated retina began to form before 26hAF. Epithelial pigmented cells were first to be distinguished from other cells at 36hAF where as pigmentation initiated by delay at 68hAF. Larvae were hatched with undifferentiated retina at major part (~72hAF). First distinct stratification was observed at 96hAF (1DAH) with 5 strata including: retina pigmented epithelium, photoreceptor cell layer, inner nuclear layer, inner plexus layer and ganglion cell layer. At 144hAF (3DAH) outer plexus layer was distinguished. The stratification was completed at early 4DAH when photoreceptor cell layer divided into two layers i.e. outer plexus layer and photoreceptor layer,. Retina was stratified completely before yolk sac depletion was completed at late 7DAF. The strata order in adult was similar to 4DAH larva, but its thickness was different. As inner nuclear layer thickness was decreased but photoreceptor layer thickness was increased.