Pisaster ochraceus
| Pisaster ochraceus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Pisaster ochraceus , Ganges Harbor ( British Columbia ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Pisaster ochraceus | ||||||||||||
| ( Brandt , 1835) |
Pisaster ochraceus is a species of starfish from the order of the pincer stars (Forcipulata), which is common on the North American Pacific coast . As the main enemy of the California mussels , it is considered a key species in the local ecosystem.
features
Pisaster ochraceus has five strong arms that are 10 cm to 25 cm long and are not clearly separated from the mouth disc. Unlike some other species, the thickest part of the arms is at the base. The starfish are mostly purple, but can also be orange, orange-ocher, yellow, reddish or brown. The calcareous spines in the skin of the upper side do not exceed 2 mm in length and are arranged on the central disc in a reticulated or pentagonal pattern. The suction feet have particularly powerful suction discs in adaptation to the strong surf, with which the starfish can hold on to the rocky ground very well.
Pisaster ochraceus can easily be confused with three other species: Pisaster giganteus has blue rings and white to pink spines, while Pisaster brevispinus is pink with small white spines. Evasterias troscheli has a smaller central disk and longer, pointed arms, the thickest point of which is somewhat outside of the base and not directly on it, as in Pisaster ochraceus .
Reproduction
Like other starfish, Pisaster ochraceus is sexually separate, and males and females can only be differentiated by the presence of egg cells or sperm in the gonads.
In each arm there are two gonads made of feather-like tubes near the mouth disc. The germ openings cannot be seen with the naked eye and can only be seen when the germ cells are released. The egg pieces are orange and the testicles are whitish. As the reproductive cells mature, the reproductive glands swell and can take up 40% of the body's weight.
The germ cells are released in Puget Sound between May and July. The egg cells are fertilized in open water, and Pisaster ochraceous , like other starfish, develops through several free-swimming larval stages.
While many other starfish live to be around 4 years old, Pisaster ochraceus can live up to 20 years.
Distribution and occurrence
Pisaster ochraceus occurs on the North American Pacific coast from Prince William Sound in Alaska to Point Sal in Santa Barbara County in California . The subspecies Pisaster ochraceus segnis lives in warmer sea water from Santa Barbara County to Baja California . The starfish lives in large numbers on rocks and on mussel beds in the intertidal zone to a depth of about 90 m. Young animals are often found in crevices and under rocks. Pisaster ochraceous can tolerate a weight loss of up to 30% of its body weight.
nutrition
As a larva, Pisaster ochraceus feeds on plankton by filtering , but after metamorphosis into an adult it lives as a carnivore.
Pisaster ochraceus eats a wide variety of animals, primarily blue mussels like Mytilus californianus and Mytilus trossulus . Other prey include chitons , limpets , various other snails , barnacles , barnacles , sea urchins and decapods .
Pisaster ochraceus uses its suction cups to open mussels. If the mussel has to open the shells to breathe, this is the opportunity for the starfish to pull the shells further apart. It is able to force parts of the everted stomach into a narrow gap between the mussel shells and release digestive enzymes. The mussel is pre-digested in its shells ( extraintestinal digestion ) and ingested by the starfish by invading the stomach. It is estimated that a Pisaster ochraceus can eat around 80 California mussels a year.
Enemies
Pisaster ochraceus has few natural enemies: sea otters and gulls . The main enemy is considered to be humans , who collect starfish as collectibles.
Ecological importance
The ecosystem on California's Pacific coast has been studied for decades. Pisaster ochraceus is classified as a key species in the food structure of the tidal zones there . As the predator of the Californian mussel Mytilus californianus, it reduces its frequency so that other animals can also live there. In a field experiment by Robert T. Paine in the 1960s, Pisaster ochraceus was collected, so that Mytilus californianus multiplied en masse and displaced other species . Therefore, the presence of Pisaster ochraceus is considered essential for the conservation of biodiversity in the intertidal community of California.
literature
- Howard M. Feder: Asteroidea , in: Robert Hugh Morris, Donald Putnam Abbott, Eugene Clinton Haderlie: Intertidal Invertebrates of California . Pp. 117–135, here pp. 125, 8.13: Pisaster ochraceus Brandt, 1835 . Stanford University Press, 1st ed., Stanford (CA, USA) 1980.
- Carlos Robles: Pisaster ochraceus . In: John M. Lawrence (Ed.): Starfish - Biology and Ecology of the Asteroidea . Johns Hopkins University Press. Baltimore 2013. pp. 161-173.
- J. Nybakken: Diversity of the invertebrates . California State University, Hayward 1996.
Web links
- Y. Ramirez: Pisaster ochraceus . Animal Diversity Web, 2002.
- Pisaster ochraceus (Brandt, 1835) . Encyclopedia of Life.
- wikis.evergreen.edu
- seanet.stanford.edu
- bss.sfsu.edu
- wallawalla.edu
- enature.com
- eol.org
- The Biogeography of the Purple Ocher Sea Star ( Pisaster ochraceus ) San Francisco State University
- Ocher Sea Star , North Island Explorer
Individual evidence
- ^ EN Kozloff (1996): Marine Invertebrates of the Pacific Northwest. Seattle: University of Washington Press.
- ↑ a b c d M. McFadden (2002): Pisaster ochraceus. ( wallawalla.edu ( Memento of the original from April 12, 2009 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. ).
- ↑ a b J. Nybakken: diversity of the invertebrates . California State University, Hayward 1996.
- ↑ a b Pisaster ochraceus (Brandt, 1835). In: Encyclopedia of Life. ( eol.org ).
- ^ V. Humphreys: The Biogeography of the Purple Ocher Sea Star (Pisaster ochraceus). 2003 ( bss.sfsu.edu ( Memento of the original from May 29, 2009 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this note. ).
- ↑ CDG Harley, MS Pankey, JP Wares, RK Grosberg, MJ Wonham: Color Polymorphism and Genetic Structure in the Sea Star Pisaster ochraceus . In: The Biological Bulletin . 211, No. 3, 2006, pp. 248-262. doi : 10.2307 / 4134547 . PMID 17179384 .
- ^ Lovell Langstroth, Libby Langstroth, Todd Newberry: A living bay: the underwater world of Monterey Bay . Google Books, 2001, p. 29.
- ^ Edward K. Ricketts, Jack Calvin, Joel Hedgepeth: Between Pacific Tides , 5th. Edition, Stanford University Press, 1985, ISBN 978-0-8047-2068-7 , pp. 217 (accessed May 13, 2013).
- ^ Robert T. Paine : Food Web Complexity and Species Diversity. In: The American Naturalist. Volume 100, No. 910, 1966, pp. 65-75, doi: 10.1086 / 282400
- ^ Mary E. Power et al .: Challenges in the quest for keystones . BioScience 46.8 (1996), pp. 609-620.
- ↑ K. Holsinger (2005): Keystone species. ( darwin.eeb.uconn.edu ( Memento of the original from June 30, 2010 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. ).
