No other class of animals has explored and exploited eye development as thoroughly as the amphipods. Some representatives in the group are considered blind. There is no evidence that their eyes perform a visual function. At the other end of the spectrum are some of the most spectacular examples of compound eye development in the animal kingdom.

More than one family of open ocean, pelagic amphipods have decided that heads are for seeing. They have literally converted their entire head region into spectacular prismatic compound eyes, capable of receiving light from almost any direction - including through their own transparent bodies! The three examples shown here are from very distinct families with very different habits and yet each has extraordinarily elaborate compound eyes.

	Amphipod Compound Eyes (Parathemisto) Photograph by Peter Parks © 2001 by Image Quest 3-D Read our copyright notice
One group, represented by Parathemisto, is amongst the most successful and widespread group in the world. They occur in nearly all latitudes and at nearly all depths. They are exceedingly active - amongst the fastest of marine crustacea and they are built like terminator robots.

	Hyperiid Amphipod Eyes - parasitic on lobate ctenophores Photograph by Peter Parks © 2001 by Image Quest 3-D Read our copyright notice
A second group are their antithesis. They are parasitic on jellies and comb-jellies. They are slow moving, creepy sort of characters with heads shaped like the Hope Diamond in the Smithsonian Museum - facetted on every aspect and extremely prismatic when caught in the light.

Deep Sea 'Pram Bug' Amphipod in Salp - Phronima Photograph by Peter Parks © 2001 by Image Quest 3-D Read our copyright notice

The third group is related to a famous and deep water group that contains the barrel-living Phromina. This related species, swims free and needs obviously to look upwards. Its large head is a mass of omatidia directed vertically upwards and the lower section of the head consists of closely packed, red pigmented retinal columns. The mouthparts of all the species are pushed back close to the next body section and seldom occupy more than a few per cent of the cranial capacity.

This article was written by Peter Parks

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