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.

Author: Kazragor Tojajinn
Country: Liechtenstein
Language: English (Spanish)
Genre: Love
Published (Last): 24 November 2011
Pages: 446
PDF File Size: 20.81 Mb
ePub File Size: 2.59 Mb
ISBN: 122-9-33155-544-5
Downloads: 48732
Price: Free* [*Free Regsitration Required]
Uploader: Samushura

Most sipunculan species are dioecious.

Xenacoelomorpha Xenoturbellida Xenoturbella Acoelomorpha acoels nemertodermatids. The downward and upward sections of the gut are coiled around each other, forming a double helix. Because of their long-lived larval stages, many sipuncu-lan species seem to be very widespread. 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.

Phascolion strombus, an inhabitant of gastropod shells, is able to irrigate its shell to increase oxygen content by contractions of the body wall musculature.

Distinguished by fulum of longitudinal muscle bands: Proteinaceous, filu, hooks are often present on the distal part of the introvert and are either arranged in rings or scattered. Proceedings of the Royal Society B: 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.

Sipunculans reproduce asexually via transverse fission followed by regeneration of vital body components.

Sipunculans Animal subphyla Extant Cambrian first appearances. Scottish Journal of Geology. The specimen was provided by a friend of his, Professor Mackintosh. Themiste lageniformes is facultatively parthenogenetic.


Phylum Sipuncula

Entoprocta or Kamptozoa Siluncula moss animals. American Zoologist, 16, — A sipunculan with introvert everted left and retracted. Swimming has only been reported in Sipunculus and consists of non-directional thrashing of the trunk. The nervous system consists of a nerve ring the cerebral ganglion around the oesophagus, which functions siluncula a brain, and a single ventral nerve cord that runs the siouncula of the body. The ratio between introvert and trunk length varies among species.

Chaetognatha arrow worms Gnathostomulida jaw worms. These are proteinaceous, non-chitinous specializations of the epidermiseither arranged in rings or scattered. These gametes are then picked up by the metanephridia system and released into the aquatic environment, where fertilisation takes place. Relatively little is known about the behavior of sipunculans. A sipunclua species was later described as Golfingia macintoshii by E.

Many species are negatively pho-totactic and retreat into sediment or rock when given siouncula opportunity. Sipunculans occur in cold, temperate and tropical marine benthic habitats. 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: When the introvert is retracted in these animals, the anal shield blocks the entrance to its burrow.

List of bilaterial animal orders. The digestive tract of sipunculans starts with the esophagus, located between the introvert retractor muscles. Originally classified as annelidsdespite the complete lack of segmentation, bristles and other annelid characters, the phylum Sipuncula was later allied with the Molluscamostly on the basis of developmental and larval characters.

Phylum Sipuncula

Arthropoda arthropods Tardigrada siouncula. Trunk length varies from a few millimeters to about The planktotrophic pelagosphera lasts up to six months in the water column before settling.


The first species of this phylum was described in by the French zoologist Henri Marie Ducrotay de Blainville who named it Sipunculus vulgaris. Some evidence points towards their involvement in ultrafiltration.

In the early seventeenth century, Sipuncula were considered close relatives of holothurians. By using this site, you agree to the Terms of Use and Privacy Policy. Since the s, there is general agreement that sipunculans are protostomes and closely related to annelids and mollusks, but their exact position still remains unresolved. In Quatrefages erected the group Gephyrea, which he considered an intermediate between worms and holothurians and which also contained echiurans, sternaspids, and priapulids.

Larval development and metamorphosis in Sipuncula.

Sipuncula – Wikipedia

The body wall surrounds the coelom that is filled with fluid on which the body wall musculature acts as a hydrostatic skeleton to extend or contract the animal. Bulletin of Marine Science, sipuncua 2— No sexual dimorphism is known in Sipuncula.

Gnathifera Chaetognatha arrow worms Gnathostomulida jaw worms. Others inhabit empty mollusk shells, polychaete tubes, foraminiferan tests, or barnacles.

When threatened, Sipunculids can contract their body into a shape resembling a peanut kernel —a practice that has given rise to the name “peanut worm”. Commonly up to 6 in 15 cm long, sometimes reaching 10 in 25 cm ; introvert up to sipunxula of trunk length.