The strange symmetry of starfish
Created | Updated Jan 28, 2002
Starfish, or, as Americans prefer to call them, sea-stars, or, as biologists prefer to call them, asteroids, are one of the five classes of living echinoderms. Crinoids (sea lilies), echinoids (sea urchins), holothurians (sea cucumbers) and ophiuroids (brittle-stars) are the other four, and though displaying extremely varied body shapes, the quintet share a number of unique features that show how closely related they really are.
The term echinoderm comes from "echinos", the Greek word for the hedgehog, and "derma", the word for skin, in reference to the spiky or spiny exteriors of some forms, such as the Crown-of-thorns starfish, infamous for its capacity for eating coral reefs. However, not all echinoderms would be painful to tread on - sea cucumbers are generally rather soft and squishy - so a more consistent set of characteristics is used to define the phylum:
Characteristic 1. A body of crystals
(to be continued)
The term echinoderm comes from "echinos", the Greek word for the hedgehog, and "derma", the word for skin, in reference to the spiky or spiny exteriors of some forms, such as the Crown-of-thorns starfish, infamous for its capacity for eating coral reefs. However, not all echinoderms would be painful to tread on - sea cucumbers are generally rather soft and squishy - so a more consistent set of characteristics is used to define the phylum:
Characteristic 1. A body of crystals
(to be continued)
