DEVELOPMENT OF THE EYE AND OPTIC LOBE OF OCTOPUS

The development of the lens, retina and optic lobes was followed in Octopus australis and O. pallidus, two species that produce benthic larvae and can readily be reared in the laboratory from egg to adult. The inner part of the lens starts to form at Naef's stage IX, and consists of a central core with overlying layers formed from processes of the lentigenic cells. Microvilli occur on the surface of the lens, and cilia and microvilli are visible in the retina, which at this point, however, is undifferentiated. The optic lobes have not started to form. The outer part of the lens starts to develop from stage XVI. Cellular differentiation of the retina, through cell nuclei crossing the basement membrane, starts at stage XV, with rhabdome development occurring from stage XVI onwards. The optic lobes are clearly formed at stage XII, but only start to differentiate and show layering from stage XVI. At hatching all adult structures are clearly visible, although considerable quantitative changes still occur before the final adult form is reached. The development of the visual system of Octopus is similar to that of several species of decapod previously reported.