Superphylum: Lophotrochozoa/ Mollusca
The Sipuncula, or peanut worms, are marine in cold and warm waters, and 320 species have been found in shallow waters. Some of the worms burrow into sand and mud and also bore into solid rock and bone to make protection for themselves, while others live in discarded shells (for example, from a hermit crab). Certain species populate in mats of algae, in large sponges, or in the roots of sea grass and mangrove trees. The majority of Sipunculid worms are less than 10 centimeters long (but in some cases, grow up to 50 cm long). And found in intertidal pools, and inhabit the sea floor all around the world.
• Body is divided: an unsegmented trunk & a narrower, retractable anterior section, "introvert" (long extendible proboscis)
• Body wall is a non-ciliated epidermis, which is overlaid by an outer layer of circular and an inner layer of longitudinal muscle
• Body wall surrounds coelom, the body cavity filled with fluid (acts as a hydrostatic skeleton)
• Introvert retracts into the trunk when threatened, to look like a peanut( 6-7 cm stretched) (Retractable via 2 pairs of retractor muscles; Protruded from trunk by forcing the fluid in the body cavity forward)
• Mouth is at anterior end of introvert
• Tentacles at end of introvert
-used to gather detritus from the water
-hallow and extended by hydrostatic pressure
• Hooks near mouth on introvert
Digestive System- begins with the esophagus (between introvert retractor and muscles), the intestine is in the trunk of the Sipuncula body, and forms a loop, and turns again; gut becomes coiled and forms a double-helix. At the front end of the gut, the rectum emerges and ends in the anus. Diet mainly consists of detritus.
Circulation System- NO BLOOD SYSTEM! the coelom transports fluid and gas exchange (by the respiratory pigment, haemerythrin, and the tentacles).
Nervous System- A Nerve Ring (the cerebral ganglion) which functions as a brain, and 1 ventral nerve cord that is the length of the body. Contain ocelli (like light sensitive receptors)
Reproductive System- Sipuncula worms reproduce sexually and asexually(less common). Peanut Worms reproduce asexually by transverse fission which is followed by the regeneration of crucial body components. They also reproduce sexually, and are considered dioecious. Gametes are produced internally in the coelom lining, where they are stored and matured until released into the water where fertilization takes place.
Impact on the World/Humanity:
The Sipuncula worms are very interesting species because there are very few species with an extending proboscis.
Sipuncula are commonly called peanut worms. Only about 320 species have been found and described. These worms live in all temperatures of water, but are mostly found in shallow waters. Depending on the species, they make their homes in the sand, in shells, or in crevices in rocks.
The Sipuncula body is unsegmented. At the top of the introvert is the mouth, which is surrounded by a ring of tentacles. The coelom is filled with free floating cells (hemerythroytes). No true circulatory or respiratory system systems! The coelom fluid transports nutrients and oxygen to all parts of the body(nephridia filters the coelomic fluid).
Introduction to the Sipuncula, by UCMP. (n.d.). UCMP - University of California Museum of Paleontology. Retrieved December 9, 2010, from http://www.ucmp.berkeley.edu/sipuncula/sipuncula.html
Peanut Worms: Sipuncula - Physical Characteristics, Behavior And Reproduction, No Common Name (sipunculus Nudus): Species Account - GEOGRAPHIC RANGE, HABITAT, DIET, PEANUT WORMS AND PEOPLE, CONSERVATION STATUS . (n.d.). Animal Life Resource. Retrieved December 9, 2010, from http://animals.jrank.org/pages/1715/Peanut-Worms-Sipuncula.html
Peanut worm. (n.d.). Race Rocks Ecological Reserve/Marine Protected Area. Retrieved December 9, 2010, from http://www.racerocks.com/racerock/eco/taxalab/bio2002/phascolosomaa.htm
Sipuncula - Encyclopedia of Life. (n.d.). Encyclopedia of Life. Retrieved December 9, 2010, from http://www.eol.org/pages/8871
Sipuncula - Wikipedia, the free encyclopedia. (n.d.). Wikipedia, the free encyclopedia. Retrieved December 9, 2010, from http://en.wikipedia.org/wiki/Sipuncula
Sipuncula : Anatomy. (n.d.). 1000s of Museums Online : MuseumStuff.com. Retrieved December 9, 2010, from http://www.museumstuff.com/learn/topics/Sipuncula::sub::Anatomy
Skeel, M. E. (n.d.). What are sipunculids (peanut worms)? (Invertebrate phylum Sipuncula) - by M E Skeel - Helium. Helium - Where Knowledge Rules. Retrieved December 9, 2010, from http://www.helium.com/items/1274412-what-are-peanut-worms