|A small selection of the many feather stars found|
during a Deep Dredge on Day 3
Prof Charles G Messing shares:
These animals, technically known as crinoids, are close relatives of sea stars, sea urchins and sea cucumbers. They have a small cup-like body and long feather-like arms that they use for filtering plankton from the water. Different species range from only a few centimeters across with ten arms, to over 30 centimeters across with more than 100 arms.
Almost all of them have a ring or cluster of hooks on the underside for anchoring to rocks, sponges or soft corals. Despite their apparently sedentary lifestyle, however, they can crawl from place to place and some can even swim with graceful undulations of their arms.Feather stars are also homes for remarkable creatures that blend perfectly with their homes. As I have heard Prof Charles explain, feather stars are condominiums! Shrimps, worms and even fishes of all kinds many be found them. Even tinier creatures may live on these animals! Here's a photo of a crinoid snapping shrimp covered with tiny white copepods, found during the Southern Expedition, shared by Dr Arthur Anker.
Some sit in the open, others extend their arms from crevices on the reef, and still others crawl from daytime hiding places to night-time feeding perches.
Feather stars come in every color and combination; in some cases one species may exhibit a wide palette, while others come in only one or two colors.
Crinoids were first discovered here by shore collectors in the mid-nineteenth century. The first one described in the scientific literature was a unique specimen that remained unknown anywhere else in the tropical Indian or western Pacific oceans. It differed from another species found across much of the region in one small but curious character; as a result it was maintained as a distinct species.
One of the reasons I looked forward to participating in this biodiversity survey was to search for this elusive feather star, and to see if it indeed was uniquely different from its relatives.
Fortune smiled, and I found numerous specimens on my first dive; in fact, the species was the first crinoid I saw on the reef. However, I also found specimens of the closely related, widespread species.
My task now is to determine whether they are just the equivalent of blue-eyed and brown-eyed individuals of one species, or actually different. This will take some detailed lab work and probably a look at their DNA.
|Photo by Dr Arthur Anker|
Day 8 of the Southern Expedition.