Phylum Sipuncula In: Atkinson LJ and Sink KJ (eds). Field Guide to the Ofshore Marine Invertebrates of South Africa,. Malachite Marketing and Media, Pretoria. Sipuncula is a clade of unsegmented, coelomate marine worms. . Sipuncula, however, with sipunculans as an annelid ingroup, other. Phylum Sipuncula. Class Phascolosomatidea. Order Aspidosiphoniformes. Family Aspidosiphonidae. Aspidosiphon Diesing, Aspidosiphon elegans.
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Two organs, likely functioning as a unit for chemoreception are located near the anterior margin of the cerebral ganglion: Three genera AspidosiphonLithacrosiphon and Cloeosiphon in the Aspidosiphonidae family, filjm epidermal structures modified for boring into rock; the anal shield is near the anteriorly located anus on the trunk just below the introvert of the animal.
Others inhabit empty mollusk shells, polychaete tubes, foraminiferan tests, or barnacles. Commonly up to 6 in 15 cm long, sometimes reaching 10 in 25 cm ; introvert up to one-third of trunk length.
Other sipunculans appear to have lived in association with corals and in vacated mollusk shells since the mid-Paleozoic, throughout the Mesozoic and Cenozoic. Sipuncula Rafinesque Invertebrate Biology, 150— Burrowing and crawling are accomplished by utilizing the introvert hooks as anchors and the introvert musculature to pull the body forward.
Most species retract their tentacles and introvert quickly following a tactile stimulus. It can be protruded from the trunk by contracting the muscles of the trunk wall, thus forcing the fluid in the body cavity forwards. Specific distribution map not available. The paleozoic Hyolitha has a mix of attributes of sipunculans and mollusks, suggesting a close phylogenetic relationship with both.
In the trunk the intestine runs posteriorly, forms a loop and turns anteriorly again. The tentacles and the contractile vessel fluid reservoir for tentacle extension contain a second coelomic compartment. This page was last edited on 6 Decemberat Longitudinal and circular body wall musculature in bands. The nervous system consists of a nerve ring the cerebral ganglion around the oesophagus, which functions as a brain, and a single ventral nerve cord that runs the length of the body.
From Wikipedia, the free encyclopedia. Most sipunculan species are dioecious. The phylogenetic placement of this phylum in the past has proved troublesome. The anus is often not visible when the introvert is retracted into the trunk. It is attached anteriorly to the body wall near the anus and posteriorly to either the body wall or inside the gut coil. Currently these two phyla have been included in a larger sipunculw, the Lophotrochozoathat also includes the annelidsthe ribbon worms and several other phyla.
Proceedings of the Royal Society B: They are found especially below the surface on tidal flats.
The specimen was dissected by Lankester between rounds of golf at Saint Andrews golf club in Scotland from which the species derives its name. Traditionally considered a phylumthey might be a subgroup of phylum Annelida based on recent molecular work. Cycliophora Symbion Annelida ringed worms.
American Zoologist, 16, — Dioecious; indirect developer with lecithotrophic trochophore and long-lived planktotrophic pelagosphera. They have been found in all depths from the intertidal zone to 22, ft 6, m. Larval development and metamorphosis in Sipuncula. This is usually prepared by cleaning the muscle and soaking it in vinegar and spices in a style similar to ceviche.
Echinodermata starfish and relatives Hemichordata acorn worms pterobranchs.
Sipuncula Peanut worms Number of families 6 Thumbnail description Sipuncjla marine worm-like animals with a body divided into a trunk and retractable introvert Photo: The tentacles each have a deep groove along which food is moved to the mouth by cilia. Nematoda roundworms Nematomorpha horsehair worms.
The body wall musculature is composed of an outer layer of longitudinal and an inner layer of circular muscles. In other projects Wikimedia Commons Wikispecies. Trunk length varies from a few millimeters to about A large coelom represents the main body cavity. Sipunculans have a body wall somewhat similar to that of annelids though unsegmented in that it consists of a non-ciliated epidermis overlain by a cuticle, an outer layer of circular and an inner layer of longitudinal musculature.
Phylogenetic analyses based on 79 ribosomal proteins indicated a position of Sipuncula within Annelida. They are relatively common in shallow waters, either in burrows or in discarded shells as hermit crabs do. Bulletin of Marine Science, 39 2— Gnathifera Chaetognatha arrow worms Gnathostomulida jaw worms.
At the termination of the gut coil, the rectum emerges and ends in the anus. The ratio between introvert and trunk length varies among species. In a few species, the trochophore does not develop directly into the adult, but into an intermediate pelagosphaera stage, that possesses a greatly enlarged metatroch ciliated band. Proteinaceous, non-chitinous hooks are often present on the distal part of the introvert and are either arranged in rings or scattered. Some sipunculan species inhabit semi-permanent burrows in coarse or silty sand, and some live in crevices under rocks.
A related species was later described as Golfingia macintoshii by E. Cosmopolitan in intertidal and shallow tropical and subtropical waters. Ot-toia prolifica from the Burgess Shale has been proposed as a fossil sipunculan, but might also be an aschelminth or Pria-pulida.
Sipunculans Animal subphyla Extant Cambrian first appearances. Entoprocta or Kamptozoa Ectoprocta moss animals.
List of bilaterial animal orders.