Pisaster giganteus
| Pisaster giganteus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Pisaster giganteus |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Pisaster giganteus | ||||||||||||
| Stimpson , 1857 |
Pisaster giganteus is a species of starfish from the order of the pincer stars (Forcipulata), whichis nativeto the North American Pacific coast andfeedsmainly on mussels and barnacles .
features
Pisaster giganteus has a compact body with five thick arms and reaches a height of about 24 cm. Despite its name, it is therefore smaller than the related Pisaster ochraceus , even if individual specimens can exceed 60 cm in size in deeper water. The top is usually light brown, sometimes also red, purple, yellowish or gray and is provided with thick, blunt spines of a bluish color with white, pink or purple, thickened tips, surrounded by pedicellariums , which serve, among other things, to protect against enemies.
Reproductive cycle
Like other starfish, Pisaster giganteus is sexually separated and the eggs are fertilized in the open sea. For this purpose, females and males come together in groups in March and April. The eggs are small and develop into bilaterally symmetrical free-swimming larvae , which after a period of time attach themselves to the substrate as plankton and metamorphose into starfish .
Habitat
Pisaster giganteus lives on the North American Pacific coast from Vancouver Island ( British Columbia ) to Baja California . It lives on rocky subsoil, sometimes also on sand, but only at the lower edge of the intertidal zone to a depth of about 88 m, because it does not tolerate dry phases as well as the related Pisaster ochraceus .
nutrition
Pisaster giganteus preferred mussels ( Mytilus californianus ) over other prey, but he also eats other shells (eg. B. Chama pellucida ), barnacles ( barnacles of the genus Balanus ), chiton and snails (z. B. limpets and worm screw ). The starfish can evert its stomach for extraintestinal digestion and force it through narrow crevices in a mussel or barnacle shell.
Pisaster giganteus occasionally eats the predatory snail Kelletia kelletii , but it shows no escape reaction . Rather, it was often observed by Rosenthal (1972) near Pisaster giganteus while the latter was eating a prey. If the starfish is consuming other prey, the advantage for the snail to get hold of its meat obviously outweighs it. Usually 2 or 3 snails use their long proboscides to scrape off meat from the prey of the eating starfish. Other starfish that Kelletia kelletii eats as commensals are Dermasterias imbricata and Pisaster brevispinus .
Predators
While the free-swimming larvae are eaten by numerous animals, Pisaster giganteus as a full-grown starfish has few enemies. These are primarily sea otters and birds , especially seagulls .
literature
- Howard M. Feder: Asteroidea , in: Robert Hugh Morris, Donald Putnam Abbott, Eugene Clinton Haderlie: Intertidal Invertebrates of California . Pp. 117–135, here p. 126, 8.14: Pisaster giganteus (Stimpson, 1857) . Stanford University Press, 1st ed., Stanford (CA, USA) 1980.
- Edward Flanders Ricketts, Jack Calvin, Joel Walker Hedgpeth, David W. Phillips: Between Pacific Tides . Fifth Edition. Stanford University Press, Stanford (California) 1985. p. 218 ( Pisaster giganteus ).
- RJ Rosenthal (1971): Trophic interaction between the sea star Pisaster giganteus and the gastropod Kelletia kelletii . Fishery Bulletin 69 (3), pp 669 -679. US Department of Commerce.
- Donald E. Landenberger (1968): Studies on Selective Feeding in the Pacific Starfish Pisaster in Southern California . Ecology 49 (6), pp. 1062-1075. doi : 10.2307 / 1934490
Web links
- Classification of Souther California Sea Stars
- Taxonomicon
- Pisaster Giganteus, SiMOn