|This section is about comatulid crinoids and the commensal creatures that rely on them for food and shelter. Select any picture for a larger view and description.|
left, also known as "feather stars" or comatulids are harmless, colorful
creatures. They are among the most ancient and primitive of ocean invertebrates. Crinoids
are Echinoderms (members of the Phylum Echinodermata, meaning "spiny skin"). To
feed, they extend their arms to catch bits of plankton or detritus (waste matter) passing
in the current, making them "suspension feeders". Tiny fingerlike tube feet that
line the featherlike arms flick passing bits of plankton into special food gutters that
run along the center of each arm; microscopic cilia carry the food along the gutter floors
to the mouth. The number of arms a Crinoid has varies widely between species; some may
have as many as 200, each up to almost 14 inches in length. Crinoids are distinguished
from other echinoderms by the fact that their mouth is pointed upward, unlike their
starfish cousins. There are nearly 550 species of comatulid crinoids worldwide.
Strictly speaking the creatures featured here are comatulids, members of the Class Crinoidea, along with sea lilies (similar to comatulids but with long stalks). Collectively, comatulid crinoids and sea lilies are referred to as crinoids, since they are both members of the Class Crinoidea. Here, as in the somewhat non-scientific SCUBA diver community, comatulids are most frequently labeled simply as crinoids or "feather stars". For complete, detailed scientific information on comatulid as well as stalked crinoids, visit Charles Messing's Crinoid Pages.
Crinoids are usually admired by divers for their bright colors, but few pause to look closely enough to see they are host to a number of tiny commensal animals, such as shrimp, clingfish, and squat lobsters. The ability of these creatures to master the art of disguise is amazing. Personally, I enjoy the tiny creatures of the reef more than the larger, pelagic animals. From a photographer's viewpoint, these tiny creatures are often better film subjects. Though photographing many of these tiny commensals on a crinoid is like chasing a squirrel around a tree, the results are very rewarding. Often the macro photograph reveals much more detail than may be seen with the naked eye.
Photography notes: As a rule, the more water between the
light source and subject, the more color that will be lost. First the red colors
disappear, then orange, yellow, green, blue, indigo, and violet, in order of decreasing
wavelength. One major advantage of close-up photography at these close distances,
typically with the subject between one and three inches from the lens, is less
water-column color filtration of the strobe's light as it travels from the
strobe to the subject and back to the camera lens. This means the colors will be more accurate
and saturated. Additionally, the shorter distances mean less chance of obstruction from
floating debris between the lens and subject.