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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The nephridiopores lie ventro-laterally, typically at the level of the anus. Sipunculans occur in cold, temperate and tropical marine benthic habitats. Commonly up to 6 in 15 cm long, sometimes reaching 10 in 25 cm ; introvert up to one-third of trunk length.
They are found especially below the surface on tidal flats. Larval development and metamorphosis in Sipuncula.
Sipuncula – Wikipedia
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. Taken in CebuPhilippines. Specific distribution map not available.
Burrowing and crawling are accomplished by utilizing the introvert hooks as anchors and the introvert musculature to pull the body forward. The worms stay submerged sipyncula the sea bed between 10 and 18 hours a day and are sensitive to salinity, and thus not commonly found near estuaries.
Abundance ranges from rare to extremely common e. The tentacles are rarely visible above the seafloor during the day, but may iflum extended at night to probe the surrounding sediment for food particles.
Longitudinal and circular body wall musculature in bands. 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.
Nitrogenous waste is excreted through a pair of metanephridia opening close to the anus, except in Phascolion and Onchnesomawhich have only a single nephridium. These are proteinaceous, non-chitinous specializations of the epidermiseither arranged in rings or scattered.
Nematoda roundworms Nematomorpha horsehair worms. The tentacles each have a deep groove along which food is moved to the mouth by cilia. The specimen was dissected by Lankester between rounds of golf at Saint Andrews golf club in Scotland from which the species derives its name. Nematoida Nematoda roundworms Nematomorpha horsehair worms.
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.
Distinguished by number of longitudinal muscle bands: The ratio between introvert and trunk length varies among species. Entoprocta or Kamptozoa Ectoprocta moss animals.
In the family Themistidae the tentacles forms a crown, as ffilum members of this group are specialized filter sipuncklaunlike the other sipunculans which are deposit feeders. The paleozoic Hyolitha has a mix of attributes of sipunculans and mollusks, suggesting a close phylogenetic relationship with both. Swimming has only been reported in Sipunculus and consists of non-directional thrashing of the trunk.
Some sipunculan species inhabit semi-permanent burrows in coarse or silty sand, and some live in crevices under rocks. The phylogenetic placement of this phylum in the past has proved troublesome. Proteinaceous, non-chitinous hooks are often present on the distal part of the fium and are either arranged in rings or scattered. The body wall musculature is composed of an outer layer of longitudinal and an inner layer of circular muscles. Two nephridia are present, except in the genera Phasco-lion and Onchnesoma, which have only a single nephridium.
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 ffilum length of the body. Gonads are only prevalent during the reproductive period.
The tentacles and the contractile vessel fluid reservoir for tentacle extension contain a second coelomic compartment. The digestive tract of sipunculans starts with the esophagus, located between the introvert retractor muscles. The mouth is located at the anterior end of the supuncula in the order Sipunculideathe mouth is si;uncula by a mass of 18 to 24 ciliated tentacleswhile in the order Phascolosomatideathe tentacles are arranged in an arc above the mouth, surrounding the nuchal organalso located at the tip of the introvert.
Arthropoda arthropods Tardigrada waterbears. The anus supuncula dorsally, usually at the anterior end of the trunk, except in some species where it is shifted anteriorly onto the introvert. At the posterior end of the trunk, a hardened caudal shield is sometimes present in Aspidosiphon ;  this may help with anchoring the animal in its burrow or may be used in the boring process.