Asteroidea

Taxonavigation

Kingdom: Animalia

Sub Kingdom: Eumetazoa

Super Phylum: Bilateria:Deuterostomia

Phylum: Echinodermata

Sub Phylum: Asterozoa

Class: Asteroidea

Order: Brisingida - Forcipulatida - Notomyotida - Paxillosida - Spinulosida - Valvatida - Velatida

Introduction

Typically referred to as starfish or sea stars.

Sea stars generally have five arms as a continum from the central disc and the length can vary greatly relative to the oral disc. Under the arms are distinctive ambulacral grooves containing the tube feet which converge at the centre of the oral disc at the mouth. The upper surface of the oral disc has the anus and one or more madreporites in the centre. They are detritus feeders, omnivores or predators. There has been numerous examples of sea stars breeding in captivity (see Starfish Spawning).

Classification

The class Asteroidea is divided into 7 orders^[1]:

Brisingida - deep-sea dwelling, many (6-16) long, attenuated arms used in suspension feeding
Forcipulatida - have forcipulate pedicellariae, which are conspicuous on the body surface
Notomyotida - deep-sea dwelling, flexible arms with characteristic longitudinal muscle bands along the inner dorsolateral surface
Paxillosida - can bury themselves partially under sandy sediments, characterised by pointed, unsuckered tubefeet
Spinulosida - relatively delicate skeletal arrangement and completely lack pedicellariae
Valvatida - quite diverse, characterized by their conspicuous marginal ossicles
Velatida - typically thick body with large discs and interradial depressions