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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Fluid transport and gas exchange are instead accomplished by the coelomwhich contains the respiratory pigment haemerythrinand the tentacular system. Gnathifera Chaetognatha arrow worms Gnathostomulida jaw worms.
It is a common meal for fisherfolk and is a sought-after but not so common appetizer in city restaurants. The paleozoic Hyolitha has a mix of attributes of sipunculans and mollusks, suggesting a close phylogenetic relationship with both. Cosmopolitan in temperate, subtropical, and tropical waters in subtidal zone to 2, ft m depth. Swimming has only been reported in Sipunculus and consists of non-directional thrashing of the trunk.
The phylum Sipuncula contains two classes, four orders, six families, 17 genera, and species. Sipuncula Peanut worms Number of families 6 Thumbnail description Unsegmented marine worm-like animals with a body divided into a trunk and retractable introvert Photo: Views Read Edit View history. They are relatively common in shallow waters, either in burrows or in discarded shells as hermit crabs do.
Platyhelminthes flatworms Gastrotricha hairybacks. In Quatrefages erected the group Gephyrea, which he considered an intermediate between worms and holothurians and which also contained echiurans, sternaspids, and priapulids. Commonly up to 6 in 15 cm long, sometimes reaching 10 in 25 cm ; introvert up to one-third of trunk length.
Sipuncula – Wikipedia
A related species was later described as Golfingia macintoshii by E. The intestine is characteristically U-shaped, with the ascending and descending branches coiled around each other in filuk double helix.
Proceedings of the Royal Society B: In the trunk the intestine runs posteriorly, forms a loop and turns anteriorly again. In Aspidosiphon the shield is a hardened, horny structure; in Lithacrosiphon it is a calcareous cone; in Cloeosiphon it is composed of separate plates. Some scientists once hypothesized a close relationship between sipunculans and the extinct hyolithsoperculate shells from the Palaeozoic with which they share a helical gut; but this hypothesis has since been discounted.
The body wall musculature is composed of an sipunckla layer of longitudinal and an inner layer of circular muscles. It can be protruded from the trunk by contracting the muscles of sjpuncula trunk wall, thus forcing the fluid in the body cavity forwards.
Sipunculans Animal subphyla Extant Cambrian first appearances. This sipunculid worm dish is made by adding vinegar and sipunclua spices. Nitrogenous waste is excreted through a pair of metanephridia opening close to the anus, except in Phascolion and Onchnesomawhich have only a single nephridium. Sipunculans occur in cold, temperate and tropical marine benthic habitats. The tentacles are rarely visible above the seafloor during the day, but may be extended at night to probe the surrounding sediment for food particles.
Sipunclans do not have a vascular blood system. The ratio between introvert and trunk length varies among species. The worms, especially in dried sipuncupa, are considered a delicacy in Vietnam as well, where they are caught on the coasts of Minh Chao island, in Van Don District.
Relatively little is known about the behavior of sipunculans. The planktotrophic pelagosphera lasts up to six months in the water column before settling.
Proteinaceous, non-chitinous hooks are often present on the distal part of the introvert and are either arranged in rings or scattered. The worms stay submerged in the sea bed between 10 and 18 hours a day and are sensitive to salinity, and thus not commonly found near estuaries.
Scottish Journal of Geology. Sipunculids are all marine. Echinodermata starfish and relatives Hemichordata acorn worms pterobranchs. Fossilized burrows possibly created by sipunculans in soft sediments are known from early and mid-Paleozoic times.
One or two pairs of prominent introvert retractor muscles are present. Trunk length varies from a few millimeters to about Number of families 6 Thumbnail description Unsegmented marine worm-like animals with a body divided into a trunk and retractable introvert Photo: The sipunculan body is divided into an unsegmented, bulbous trunk and a narrower, anterior section, called the “introvert”.
Some evidence points towards their involvement in ultrafiltration. The tentacular system connects the tentacles at the tip of the introvert to a ring canal at their base, from which a contractile vessel that runs along the esophagus and ends blindly posteriorly. Other sipunculans appear to have lived in association with corals and in vacated mollusk shells since the mid-Paleozoic, throughout the Mesozoic and Cenozoic. Dioecious; indirect developer with lecithotrophic trochophore and long-lived planktotrophic pelagosphera.
List of bilaterial animal orders. Wikimedia Commons has media related to Sipuncula. These are proteinaceous, non-chitinous specializations of the epidermiseither arranged in rings or scattered. Phylogenetic analyses based on 79 ribosomal proteins indicated a position of Sipuncula within Annelida. In the family Themistidae the tentacles forms a crown, as the members of this group are specialized filter feedersunlike the other sipunculans which are deposit feeders.