Organisms may develop exaggerated morphologies for a variety of reasons. One is cosmetic, as in the male
Peacock and his tail; other reasons may be purely functional. Compound eyes, such as those that occur in
arthropods on Earth, are made up of a number of simple light sensors marked by hexagonal or pentagonal
facets on the surface of the eye. These facets work together to generate an image. Such eyes are excellent at
detecting movement, but generate low resolution images, unless they are very large. For an insect eye to
provide the same visual acuity as a human eye, it would need to be one metre across!
On the planet Procyon-beta, the inhabitants have enormous eyes for both these reasons. Each visible facet is
actually an array of light-sensors in this case, and large eyes are needed to provide acuity, however, the eyes
are larger than needed, since they are considered an item of beauty and so are selected for.
Having such eyes provides a number of problems that need to be overcome. Such large eyes would be extremely
heavy if filled with fluid. In the Procyonians each eye contains a normal of internal air-sacs that reduce the weight
of these structures considerably. Procyon also has a slightly low gravitational field (0.6 G). Nevertheless large
neck muscles are present to bear the weight. The head also does not have to turn much since the eyes provide
good 360-degree vision!
One might think that such structures would be susceptible to damage, undesirable in such a useful organ.
However, the polysaccharide shell enclosing each eye has a hardness equivalent to bronze alloy, but at a
fraction of the weight, so the eyes are very robust. Nevertheless, if damaged then another eye grows inside the
shell of the other eye and eventually replaces it as the defunct eye is cast-off.
Such large eyes also incur energy costs during locomotion. When walking, the centre of gravity of the body must
be maintained, and although the eyes are quite light, their weight is counterbalanced by the forked tail (which also
contains taste sensors in its two tips). During running the large eyes create drag, however, unlike humans, the
Procyonians never evolved as hunters, rather they obtain their nutrients from symbiotic a photosynthetic orange
organism (the orange colour being due to accessory pigments harboured inside endosymbiotic micro-organisms
which masks the photosynthetic pigments which are normally yellow-green in this instance) which dominates vast
swathes of Procyon's vegetation. This organism also 'infects' the skin of the Procyonians, furnishing them with
green photosynthetic cells which, together with rich nectaries produced by the same organism, provides the
Procyonians with all their nutritional needs. In return the Procyonians nurture and protect their provider. This
relationship is an ancient one which evolved naturally in distant prehistoric times. Thus, Procyonians do not often
need to run great distances, though they can move quickly when they want to, this speed being facilitated by their
great stature (Procyonians are typically 8-9 feet tall).
Another problem with these large eyes is the large amount of sensory data that must be processed, especially
with the 360 degree vision. Large optic lobes occupy a large part of the eyestalks and they filter the information
such that only about 120 degrees of the visual field is perceived in high resolution at any one time (the brain is
able to switch its field of focus).
Above: Procyon-beta. This planet has a modest gravitational field (0.6 G) and has
consequently slowly lost water vapour over time, as molecules are lost from its atmosphere at
a higher rate than on higher gravity planets. The biosphere has compensated by producing
more water and by generating large numbers of airborne micro-organisms which seed the
clouds, generating rain, and give them their yellow colour.