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Phylum Echinodermata. Colton and Victoria. Taxonomic Classification. 7,000 species of echinoderms Class Asteroidea (sea star, Ophiuroidea brittle stars), Echinoidea (sea urchins and sand dollars) and Holothuroidea (sea cucumbers Crinoidea (feather stars and sea lilies ).
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Phylum Echinodermata Colton and Victoria
Taxonomic Classification • 7,000 species of echinoderms • Class Asteroidea(sea star, • Ophiuroideabrittle stars), • Echinoidea(sea urchins and sand dollars) and • Holothuroidea(sea cucumbers • Crinoidea(feather stars and sea lilies)
Key Characteristics • Echinoderms are characterized by radial symmetry • 5 or more arms radiating from a central body • In each segment there is copies of the internal organs • They have no heart, brain, nor eyes, but some brittle stars seem to have light sensitive parts on their arms. • Their mouth is on the underside and their anus on top. • Echinoderms have tentacle-like structures called tube feet with suction pads at their extremities.
Adaptations to the Marine Environment Echinoderms live in marine habitats, although they can occasionally survive being washed up and dried on shore. Within marine habitats, Echinoderms can survive in a wide variety of places. Sea Stars and sea cucumbersprefer rocky areas while others often reside in sandy areas where they can bury themselves. Some Echinoderms even use other animals as homes such as the skin of other fish. In order to stay concealed during the day, Echinoderms have adapted to match the color of their surroundings. Another adaptation the Echinoderms have is that they can regenerate body parts. For example, if a sea star's leg gets cut off by a predator, over time it can form a new one.
Habitat Needs Most echinoderms are benthic organisms found in marine environments. Echinoderms inhabit depths ranging from shallow waters at tide lines to the deep sea. Echinoderms are globally distributed in almost all depths, latitudes and environments in the ocean. They reach highest diversity in reef environments but are also widespread on shallow shores.While almost all echinoderms are benthic,some sea-lilies can swim at great velocity for brief periods of time, and a few deep-sea sea cucumbers are fully floating. Some attach themselves to floating logs and debris.
Reproduction Sexual Reproduction • Echinoderms become sexually mature after approximately two to three years. • They are nearly allgonochoric, though a few species arehermaphroditic. Asexual Reproduction • Some of the speciesreproduce asexually byparthenogenesis. In others,the adults reproduce asexually for a while before they mature then they reproduce sexually. • In most of these species, asexual reproduction is by transverse fission with the disc splitting in two. Regrowth of both the lost disc area and the missing arms occur so that an individual may have arms of varying lengths. • Ina few species of sea stars, a single severed arm can grow into a complete individual over a period of several months. In at least some of these species, they actively use this as a method of asexual reproduction.
Facts • Echinoderm also means hedgehog-skin in Greek; most Echinoderms have spiny skin. • There are 6000 living species known in this phylum. • Echinoderms are considered the most advanced group of invertebrates.
Further Information http://www.cbv.ns.ca/mchs/diversity/EchinodermPage1.html http://marinelife.about.com/od/invertebrates/p/echinoderms.htm
