Int. J. Dev. Biol. 48: 685 - 686 (2004)
Special Issue: Eye Development
Preface
Open Access | Published: 1 November 2004
Abstract
A necessary limitation of any compilation on eye development is precisely its strength: the field is so broad and intensively studied that it is not possible to do it justice in one issue. Eyes are widely distributed and diverse. Simple organelle eyespots exist in protozoa and unicellular alga, and highly simplified eyes are present in larvae of sponges and jellyfish. Adult cubomedusan jellyfish have sophisticated eyes (ocelli) with ciliated photoreceptors (like vertebrates) and cellular lenses as well as lens-less ocelli; ancient flatworms, marine annelid worms and the protochordate ascidian larva have complex eyes with a rudimentary lens, photoreceptors and pigment cells. Insects have both lens-containing ocelli like the jellyfish and compound eyes that comprise hundreds of separate facets, the ommatidia, each with their own few rhabdomeric photoreceptors. Some shrimps have compound eyes to detect polarizing signals from each other, while other crustacea use specialized eyes to capture stray photons created by thermal vents in the depths of the ocean. Scallops use rows of mirrored, camera-type eyes with lenses along the mantle that cast focussed images on double retinas using separate phototransducing pathways to feed or evade prey. Salmon have specialized cones in their retina that appear transiently in geometric patterns to orient polarized light for the fresh water stint of their extensive migrations. The eyes of the 'four-eyed' surface fish, Anableps, are divided into a dorsal half used in air above the water surface and a ventral half submerged in water; each half uses the same lens but has a separate cornea and retina. Mice see shades of grey and ultraviolet; eagles and butterflies see brilliant color. The human eye serves us well, but we lack the resolution of the eagle, or the night vision of the owl, or the ultraviolet vision of the mouse and insects. These are but a sprinkling of eyes populating our planet. This Special Issue of The International Journal of Developmental Biology touches on the development of some of these remarkable eyes, regrettably few, but we hope it kindles your interest to learn more.