Kingdom: Animalia
Phylum: Echinodermata
Subphylum: Asterozoa
Class: Asteroidea Starfish are among the most familiar of marine invertebrates. They typically have a central disc and five arms, though some species have more than this. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates. Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown. Starfish have tube feet operated by a hydraulic system and a mouth at the centre of the oral or lower surface. They have complex life cycles and can reproduce both sexually and asexually. Most can regenerate damaged parts or lost arms and they can shed arms as a means of defence ring canal
Circular canal in which filtered water enters through the madreporite and branches out into the radiated canals. rectal cecum
Lateral duct of the terminal part of the digestive tract, where waste is stored before being expelled through the anus. anus Terminal orifice of the digestive tract allowing waste to be ejected; most of the undigested food is regurgitated rather than expelled through the anus. stomach Dilated section of the digestive tract preceding the intestine; it receives food to be digested. gonad Each of the two glands located in each arm, producing gametes (spermatozoids or ovules) depending on the sex of the starfish. pyloric cecum
Radiated duct of the digestive tract producing digestive enzymes and also allowing digested food to be stored. gonopore Dorsal opening through which gametes (spermatozoids and ovules) are expelled into the water to be fertilized. intestine Section of the digestive tract between the stomach and the anus where absorption of nutrients is carried out and waste is transformed into fecal matter. radial canal
Canal running the length of the arm; it receives water from the annular canal, which then passed into the tube feet. ampulla Bulb that contracts