Structural and functional analysis of ocular regions of five marine teleost fishes (Hippocampus hippocampus, Sardina pilchardus, Gobius niger, Mullus barbatus & Solea solea)

•Investigate ocular regions of five marine fishes inhabiting different depths.•Analysis of retinal histology & lens ultrastructure.•Assessments of protein expression in lens and retina.•Assessment of isoenzyme electrophoresis in retina and lens involved in visual functions.

Five marine teleost fishes inhabiting different marine depths namely Hippocampus hippocampus (Linnaeus, 1758), Sardina pilchardus (Walbaum, 1792), Gobius niger (Linnaeus, 1758), Mullus barbatus barbatus (Linnaeus, 1758) and Solea solea (Linnaeus, 1758) were used in the present study. Their retinae and lenses were subjected for histological, scanning electron microscopy, SDS-PAGE and isoenzyme electrophoresis of alkaline phosphatase, malate and glucose-6-phosphate dehydrogenase. The present findings showed variant histological structures with characteristic photoreceptors mainly of either rods for H. hippocampus, M. barbatus and S. solea or cones in S. pilchardus. Mixed photoreceptors are identified in G. niger. The fishes exhibited diversity in protein band expression coincides with change of pattern orientation in lens fibers arrangement and histological structures of retina. Isoenzyme electrophoresis of estimated isoenzyme showed differences between lens and retina of fishes especially H. hippocampus.It can be concluded that the retina and lens of the studied teleost fishes showed apparent varying structure reflecting the isoenzyme characteristic for preserving functional characteristic of vision according to the marine habitat depths.