Sipuncula


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Related to Sipuncula: Chaetognatha, Phoronida, Echiura, peanut worms

Sipuncula

A phylum of sedentary marine vermiform coelomates that are unsegmented, but possibly distantly related to the annelids; they are commonly called peanut worms. Two classes are defined: Sipunculidea and Phascolosomatidea. In all there are 17 genera and approximately 150 species living in a wide variety of oceanic habitats within the sediment or inside any protective shelter such as a discarded mollusk shell, foraminiferan test, or crevice in rock or coral.

Adult sipunculans range in trunk length from 2 to over 500 mm (0.08 to over 20 in.). The shape of the body ranges from almost spherical to a slender cylinder. Sipunculans have a variety of epidermal structures (papillae, hooks, or shields). Many species lack color, but shades of yellow or brown may be present. Internal anatomy is relatively simple. The digestive tract has a straight esophagus and a double-coiled intestine extending toward the posterior end of the body and back terminating in a rectum, sometimes bearing small cecum. A ventral nerve cord with lateral nerves and circumenteric connectives to the pair of cerebral ganglia are present. Two or four pigmented eyespots may be present on the cerebral ganglia, and a chemoreceptor (nuchal organ) is usually present.

Knowledge of the reproductive biology of sipunculans is scanty, and good information on breeding cycles is unavailable for most genera. Most sipunculans are dioecious and lack any sexual dimorphism. These worms play a part in the recycling of detritus and probably consume smaller invertebrates in the process. They are in turn preyed on by fishes and probably other predators (including humans).

References in periodicals archive ?
List of Nemertea and Sipuncula from Santiago de Cuba costs, Cuba
Scyliorhinus canicula exhibited a diverse diet, composed of 63 different taxa, belonging to eight taxonomical groups: Sipuncula, Annelida, Crustacea, Mollusca, Echinodermata, Urochordata, Chondrichthyes, and Teleostei, as well as unidentified materials (Table 1).
Spring Summer GI GII GIII GI GII GIII Polychaeta Chone insularis 351 22 Exogone arenosa 1 316 2 3 205 Aricidea taylori 9 10 142 3 115 Neanthes bruaca 12 78 32 12 16 Magelona posterenlongata 27 75 Lumbrinereis tetraura 24 96 Cirrophorus americanus 36 32 135 Mollusca Caecum striatum 601 8 Caecum pulchellum 462 8 Corbula caribea 2 78 8 75 131 Sipuncula Aspidosiphon gosnoldi 42 84 Crustacea Microphoxus cornutus 13 1 30 Phoxocephalopsis zimmeri 1 33 11 1 Ampelisciphotis podophthalma Apanthura sp.
The recognition of a segmented ancestry is in accordance with the current view of molecular phylogenetic analyses, which consider Sipuncula either as an annelid sister taxon or as ingroup annelids (McHugh.
The epifauna was composed of 46 Scaphopoda and mollusca species, 36 Fish, 33 Polychaeta, 29 Crustacea, 6 Echinodermata, 2 Cnidaria (Anthozoa), 3 Sipuncula, 1 Nemertini, 2 Ascidiacea and 1 Pycnogonida.
Cnidaria, Turbellaria, Sipuncula, Gastrotricha) during delay phase (2-7 months) between collection and observation of samples, and (ii) low efficiency of sampling strategy (i.
219-228 in Proceedings of the International Symposium on the Biology of Sipuncula and Echiura, I.