Echinodermata
Introduction:
Members of the echinoderms can be recognised by their 5-point radial symmetry and spines or bumps lining their bodies- reflected in the name echinoderm which means 'spiny skin'.
They only live in marine environments, among the sediments on the sea floor, and are found at a range of depths. From shallow coastal waters to the deep sea. They are the largest entirely marine phylum, containing over 7,000 living species
Examples of echinoderms include sea stars, sea urchins, sea cucumbers, brittle stars, and feather stars.
In the museum the echinoderms can be found in outer cabinet 17
Structure and adaptations:
Echinoderms are covered with cancerous spines which sit on top of organic tissues to allow the animal to grow without moulting. In addition to these spikes many echinoderms can appear 'hairy'. These are not hairs but rather 'tube-feet', extensions of the animal's skin. They are used for movement, feeding and gas exchange.
Most echinoderms are able to reproduce asexually as well as regenerate tissue, organs and even limbs. In some cases echinoderms can regenerate their entire body, just from a single limb!
Classification:
There are two main subdivisions in the echinoderms. These are seperated based on evoluntionary history and the mobility of the animal.
Eleutherozoa encompass the echinoderms able to freely move, whereas the Pelmatozoa are immobile echinoderms.
Eleutherozoa:
Asteroidea
Starfish
Ophiuroidea
Brittle stars
Echinoidea
Sea urchins and sand dollars
Holothuroidea
Sea cucumbers
Pelmatozoa:
Crinoidea
Feather stars and sea lilies as well as 2 extinct groups.
Explore the echinoderms more through the interactive phylogeny tree from One Zoom.
Museum Highlights:
24-rayed Sunstar, which is now possibly extinct as it hasn't been observed in it's habitat, waters surrounding Española Island, since the weather event El Nino hit the Galapagos islands in 1983
Brittle stars, known for their ability to break off limbs in order to escape predators, then grow the limb back.
Hairy Sea cumber, earning its name from the 'hair-like' podia covering it's body to aid with movement
24- rayed sunstar, Heliaster solaris
Specimen Gallery:
1. mauritius images GmbH / Alamy Stock Photo
2. Sea lily in Marianas region © NOAA Ocean Exploration and Research,