Spider Vision

Spider vision
Morehouse, Nathan
Current Biology, Volume 30, Issue 17, R975 - R980

This is a great article, and it only has 6 pages.

Morehouse summarizes what’s known about spider eyes, which come in a great variety of sizes and arrangements.

He runs down spider eye anatomy, which is complicated by many spiders having 2 kinds of eyes. He also writes about how spider brains process the information provided by the multiple eyes. Some spiders have muscles that move their retinas around inside their eyes, so even though they don’t have rotating eyeballs inside eye sockets, they can look in different direction without moving their head I mean cephalothorax, which has advantages like not alerting potential prey by moving, or not moving secondary eyes, so their view stays steady.

There’s a section on gene regulatory networks that shows the two eye types probably derive from an ancestral arthropod configuration of compound eyes on the sides of its head, and simple eyes in the middle. Apparently even highly derived insects like wasps and bees have both the famous compound eye, and ocelli that are optically “simple”. I did not know that until now.

Spider eyes are all of the type called simple, but:

Although the secondary eyes of spiders do not superficially resemble compound eyes, the argument is that these eyes represent the dispersed remnants of a modified pair of compound eyes.

And why not? Ancestral vertebrates seem to have had four eyes. Why shouldn’t spider evolution break up compound eyes and move them around on spiders’ bodies?

The paper has a 14 item bibliography that looks to mention interesting papers.

Spider Vision is available as a web page and PDF.