Echinoderm is the common name for any member of the phylum Echinodermata. It originated from Ancient Greek, echinos - “hedgehog” and derma - “skin”. This phylum exclusively lives in the oceans. They are found at every level of the ocean discovered by man so far from inter tidal zone to the abyssal zone. They can not be found on land or in freshwater. Echinoderms the second largest grouping of deuterostomes (a super phylum). The phylum contains around 7,000 living species with 13,000 known from the fossil record. They are attached to many fossil records and ecological importance in understanding the marine realm. The existing species fall into 5 different clades:
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Characteristics
- Calcitics skeleton composed of many ossicles
- There skeletons of composed of calcium and proteins. This calcite is then made into tiny crystals. Ossicle is not sold but sponge like microstructure called stereom that is only found in this phylum.
- Water vascular system
- The water vascular system takes over functions that include locomotion, respiration, and feeding.
- Mutable collagenous tissue
- The ossicles in echinoderms are many by collagenous tissue which is a connective tissue the is mutable on a quick bases. Allowing echinoderms to be loosen and rigid with its tissue creativing various position the echinoderm can hold for a period of time with no muscular energy.
- Pentaradial body organization in adults
- Some echinoderms have evolved a five-fold symmetry but it is only common in a few clades.
Reproduction
Sexual reproduction happens where an sperm and egg spread through open water where fertilization happens. Yet some species of sea stars, brittle stars, and sea cucumbers go through internal fertilization. Echinoderms can produce offspring asexually this is achieved most commonly though the division of body parts called fragmentation.