Echiurans are unsegmented wormsthat range in size from 7–470 mm. The body is divided into two parts: a nonretractable anterior proboscis, and a posterior trunk. The proboscis is folded to form a ventral ciliated gutter; it is variable in length (up to 1.5 m), and in some species is highly extensible. Although the trunk appears segmented because of rows of papillae, internally it is a single sac of coelomic fluid, which serves as a hydrostatic skeleton and holds the internal organs, including the highly convoluted digestive system extending from the mouth at the anterior tip of the trunk to the anus at the posterior. Unusual structures in the echiurans are anal sacs that function as excretory organs like nephridia but empty into the anus. These and the presence of setae and a circulatory system serve to differentiate the phylum Echiura from the phylum Sipuncula. The nervous system, circulatory system, setae, and aspects of the excretory system and of the early development of the...
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Kaestner, A., 1967. Invertebrate Zoology, Vol. 1. New York: Wiley Interscience, 597p.
Schäfer, W., 1972. Ecology and Paleoecology of Marine Environments, trans. I. Oertel, ed. G. Y. Craig. Edinburgh: Oliver and Boyd, 568p.
Stephens, A. C. and Edmonds, S. J., 1972. The Phyla Sipuncula and Echiura. London: British Museum (Natural History), 528p.
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© 1982 Hutchinson Ross Publishing Company
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Miller, M.F. (1982). Echiura . In: Beaches and Coastal Geology. Encyclopedia of Earth Sciences Series. Springer, New York, NY. https://doi.org/10.1007/0-387-30843-1_162
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DOI: https://doi.org/10.1007/0-387-30843-1_162
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