Eyespots

In actual biology eyespots are simple photoreceptors more primitive than eyes. In Poseidon-based biology, eyespots are quite advanced, as the following passages by Jeff Barber of Biohazard make clear:

Eyespots was perhaps a bad choice of term, as you are not the first to ask about them. I have always liked the term however, and the impression it brings to my mind is certainly an alien one. Not being able to look a strange creature in the eye would be disconcerting at best.

Now of course, there are many creatures on Poseidon that have simplistic light sensing organs (true eyspots) and rely on other sensory media such as sound, electric fields, scent, etc. For those animals that rely on vision as their primary sense however, their BP eyespots are remarkable organs.

BP eyespots are not really eyespots at all. In fact, in many ways they are far more sophisticated than terrestrial visual systems. Most animals have two or more rows with multiple organs in each row. This typically provides several advantages; extreme peripheral, sometimes 360 degree or even spherical fields of vision, better sense of parallax and relative motion, and enhanced depth perception — advantages for both predators and prey.

The individual organs are actually shallow cavities covered by a shield of clear connective tissue similar to the cornea of terrestrial animal eyes. Within the cavity is a suspension fluid than supports dozens, and in a few cases even hundreds, of tiny 'bubble lenses'. These structures are small globules of clear, semi-solid secretions that are ringed by complex muscle groups that can adjust the focal length and direction of focus of each lens, over a considerable range. This allows the eyes to focus one or more lenses on one or more classes of retinal tissues on the inner surface of the eyespot cavity. These light sensitive tissues typically include cells sensitive to the our visible light spectrum as well as the far red and ultraviolet wavelengths. This allows each eye to optimize its sensitivity to the incident wavelengths, and allows even a single eye to focus on a variety of objects at various distances, all at the same time, and from the most obscure angles.

What organisms equipped with such eyes actually see is as hard to visualize as what dolphins 'see'; when they echolocate, but you can imagine the possible advantages. Obviously the visual cortex of these animals has to be large and well developed to control the arrays of lenses and to interpret the information they bring in. Just cut open the head of the next lesser white you encounter and you will see what I mean ; )

Jeff has also said, earlier than the previous quotation:

The reasons are mostly evolutionarily with only a sprinkle of artistic license. The ecology of Poseidon is a hostile one where every adaptive advantage may mean the difference between life and death. On Earth, animals have solved the challenge of light sensitivity and vision in many different ways:

• light sensitive eyespots on flatworms
• ultraviolet sensitive compound eyes of insects
• pin-hole eyes of some cephalapods
• pineal light sensitivity in some reptiles
• thermal pit receptors in some snakes
• enhanced light sensitivity of noctural mammals

Given the variety of real visual systems on Earth, and the evolutionarily demanding ecology of Poseidon, it was logical to create a visual organ system for Blue Planet animals that incorporated a number of advantages.

The eyespot organs of Poseidon's species are differentially sensitive to various visible, ultraviolet and infrared energy. They are also differentially adapted to motion detection, directed focus, wide angle observation and low light conditions. Though not all species share each of these capabilities, there are far more universal in the animals of Poseidon than they are in those on Earth.

Rows of multiple eyspots not only add a decidedly alien quality (artistic bit), but they also provide both prey and predators with obvious advantages: wider/multiple fields of view, directional sensitivity, and sets of organs dedicated to specific tasks (motion detection, IR sensitivity, detail descrimination, etc.)