#Legendary sea of stars skin#

Neatly arranged rows of tube feet can be found on the underside of each arm. The arms of sea stars are thick and prominent, a characteristic that sets them apart from brittle stars, their echinoderm cousins.

It is used to describe the echinoderms described in the class Asteroidea to avoid any suggestion that these invertebrates are types of fishes. Long known as starfish, “sea star” in recent years has become the more widely accepted term. In essence, the hydrovascular system is a set of internal pipes and valves that use seawater to extend and contract structures commonly called tube feet that assist the sea stars as they move about the sea floor in a slow but purposeful manner, and when they grab potential prey.īrittle stars | Getty Images You Say Starfish, I Say Sea Star This water-governed system is used in locomotion and for capturing food. The feature that distinguishes echinoderms from all other animals is the presence of a hydraulic system known as the hydrovascular, or ambulacral, system. Their nervous system is composed of a number of simple rings of nerves without any “central command headquarter.” But despite this design, echinoderms are capable of many surprisingly complex response patterns. However, in their larval stage, sea stars display bilateral symmetry with their left and right sides mirroring each another.Īll echinoderms, including sea stars, lack an organ that is considered a brain, and many scientists gleefully describe echinoderms as the most advanced of the brainless invertebrates.

The five-part symmetry is readily apparent in adult sea stars and brittle stars, and though present, this pentamerous symmetry is less obvious in sea urchins, sea cucumbers, sand dollars and basket stars. Other prominent echinoderm characteristics include bodies that display five-part radial symmetry and distinct organ systems, including tube feet.

#Legendary sea of stars skin#

Filled with thousands of nerves, the sensitive skin protects the animal and surrounds the internal skeleton. But despite its rugged appearance, the skin of most species is surprisingly delicate and easy to injure. The word “echinoderm” is derived from the Greek words “echinos,” meaning spiny, and “derma,” meaning skin, and the skin of most echinoderms is covered with spines or wartlike projections and bumps. Brainless, Spiny-Skinned CreaturesĪlong with their close cousins the crinoids, brittle stars, basket stars, sea cucumbers, sea urchins and sand dollars, sea stars are described in the phylum Echinodermata (the echinoderms). Of the sea stars found in tropical seas, the majority occurs in Indo-Pacific waters, but a number of species do occur in the Atlantic, Caribbean and associated seas. Occurring only in saltwater environments, most sea stars inhabit the sea floor in temperate and tropical seas where they play important roles as both scavengers and predators. Worldwide there are about 1,500 known species of sea stars, and sighting one or more species on a dive is quite common in many oceans around the globe. At least the part we normally see, the dorsal surface, appears as one color. Many are multicolored and mottled, but others appear in a single hue. Some sea stars display brilliant colors while others are dull and nondescript. Most have five “arms,” but others, known as sun stars, have as many as 24. Others are so large that you cannot touch your hands if you attempt to encircle a single specimen with your arms. Some species are small enough that you can easily place more than one specimen in the palm of your hand. Sea stars occur in a variety of shapes, sizes and colors. In many respects, sea stars appear to be simple animals, the kind of organism we often classify as a “lower life form,” but no matter how laymen or scientists describe them, there is little doubt that anytime we see a sea star, it tends to command our attention.

Either near the beach or as part of an undersea scene, sea stars have become one of the enduring images of the marine environment. Sea stars are the jewels of many tide pools and a highlight of many beach excursions. Our knowledge came from nursery rhymes, poems, stories about walks along the seashore, and if you were lucky, from personal encounters when you explored tide pools or vacationed at a beach. As school-age kids, long before we even thought of becoming scuba divers, almost all of us had some awareness about the marine creatures known as sea stars.