The creatures that inhabit the deeper parts of the ocean would likely seem strange to those individuals who are not biologists or oceanographers. These creatures' bizarre shapes are often the result of evolutionary changes that allow them to adapt to the extreme conditions and meager food supplies of the deep ocean. Sea lilies, or crinoids, are a near-extinct example of just this type of deep sea creature. Does this Spark an idea?
Crinoids
Crinoid is a term for any member of the Crinoidea class of the phylum Echinodermata. Crinoids are animals, though they closely resemble plants. For this reason, crinoids are often called "sea lilies." Crinoids flourished in pre-historic eras but are nearly extinct as of the time of publication. There are numerous varieties of sea lilies, classified primarily according to their appearance, but all Crinoids have three main body parts: the stem that anchors the animal to the ocean floor, the calyx, a cup-like formation containing the animal's mouth and digestive organs, and the animal's arms, the most noticeable part of a crinoid's anatomy and its main tools for gathering food.
Behavior
Although "stalkless" crinoids are capable of movement, most crinoids remain permanently attached to the ocean floor, so their only means of eating is to extend their arms into the water to catch detritus, marine snow and drifting particles from the ocean water above them. Tiny hairs that line their arms, known as cilia, filter the particles from the water and bring them to the crinoids' mouths. Pre-historic species of crinoids, as evidenced by fossil records, typically had around five legs while modern species can have up to 200; number of legs is always a multiple of five.
Extinction
Crinoids were most abundant during the Paleozoic era, particularly the Mississippian period of the Paleozoic era. About 250 million years ago, near the end of the Permian period, the biggest mass extinction event in the history of Earth occurred, quite nearly wiping out all crinoids. The few remaining species of crinoid that survived the extinction are the direct forebears of crinoids that now live in the ocean.
Other Considerations
Early species of crinoids preferred mostly shallow waters but modern crinoids typically live much deeper, 300 feet or more, though some varieties still live in shallow waters. If you want to see a crinoid up close, your best bet is to view a fossilized crinoid in a museum since most people will not have the chance to dive deep enough to see a living crinoid. Note, however, that most fossilized crinoids are incomplete since ocean currents swept away skeletal fragments after the crinoids' soft tissue decayed.
Tags: ocean floor, particles from, shallow waters, species crinoids, their arms
