The Eyes Have It

What am I looking at?

These are the cells that make up the eye of a zebrafish only about a day after fertilization. The outermost layer contains skin cells (1) that will form the skin around the eye. In the middle layer are retinal neural epithelial cells (2), which will form the retina – the part of the eye that detects light. The innermost layer contains the cells that will form the lens (3). In all of the cells, the plasma membrane is blue, the Golgi apparatus is green, the endoplasmic reticulum is purple, and the mitochondria are orange.

Click on the right arrow to see an alternate view of a developing zebrafish eye.

Biology in the background

Zebrafish eyes are similar to ours. We share all the major structures, such as a single lens to focus light, a retina with photoreceptor cells to detect light, and a liquid-filled cavity between the two – the vitreous cavity. During development, the cells of the eye and the organelles within them undergo significant changes to create a fully functional adult eye. Images like this one can provide unique insights into the organization of the developing cells and their organelles at a specific developmental stage. While these insights cannot be applied directly to the development of a human eye due to certain differences, they still provide scientists with foundational knowledge regarding the developmental process, its timing, and the requirements of the cells in the eye during development – information that can be used to set the stage for research on the eye in other vertebrates, including humans.

These cells vary in size, but those in the middle that will eventually form photoreceptors are about 15 micrometers long, or roughly five times smaller than the width of a human hair.

Technique

These images were created using confocal microscopy.