Echinoderms Anhang

Evolution: Echinoderms first appear in the fossil record during the mid-Cambrian period.

Possible echinoderm species have been traced back to the Proterozoic period and it is thought by some researchers that echinoderms existed in the Precambrian era.

This is the largest phylum without any freshwater or terrestrial forms, although some can live in brackish water.

Common features: Radial symmetry.

Echinoderm means spiny skin. Calcareous plates, called ossicles, are connected by collagen-based ligaments, under nervous control.

Mutable collagenous tissue. The collagen-based ligaments can be locked or unlocked, tight or loose, allowing a range of movement. The skeleton of echinoids (urchins) and

asteroids (starfish) can als form pedicellariae (pincer-like struct ures) as seen in Toxopneustes pileolus.

A water-vascular system: water pressure creates hydraulic power for movement, respiration and feeding. In starfish, canals radiating out from a central ring, circling the gut,

pump sea water through the body and operate the sucker-like feet (podia).

Body types: Are extremely varied. Shapes are tubular, stars, spherical, discoid, feathery, bush and basket-like.

Body system: Echinoderms possess an open, fluid-filled body cavity lined with tissue, the coelom or gut. They have a ‘mouth’ underneath, on the lower surface, and

an ‘anus’ on top. There are no specialised excretory organs. There is a non-centralised nervous system: a nerve net, but no brain. Possess gonads and the sexes are usually separate.

Only holothurians have specialised respiratory systems, and many echinoderms have only rudimentary circulatory systems; the water-vascular system takes over some of the

functions of these systems, as there is a heart tact as a pump. Capable of body regeneration, regrowing arms in the case of starfish, but the powers of regeneration in this group

go well beyond regeneration of arms.

Senses: Communication takes place by means of chemicals and pheromones. There are light-sensing organs in the skin. The non-centralised nervous system allows

echinoderms tsense the environment from all sides and provides them with their sense of touch: nerves are more concentrated in the tips of the ‘arms’ in starfish.

Conditions: Epilepsy. Hypertension. Stroke. Glandular problems. Breast cancer. Nymphomania. Migraine. Sinusitis. Flu. Oedema. Eczema. Herpes. Acne. Ulceration.

Extremities: Feet/toes/hands/fingers. Delusions about legs (being longer, shorter).

Vorwort/Suchen Zeichen/Abkürzungen Impressum