The marine Sipuncula are regarded as consisting of 1 class, 4 families, 13 genera and 367 species and subspecies. Sipuncula are widespread in the benthos of the World Ocean: from 82" N and 77" S to the equator, and from the littoral to a depth of 7000 m; 63 % of the species are confined to the shelf. Temperatures tolerated range from -1.9 to 29 "C; however, most species are found within the 20 'C isotherm. The geographical distribution is confined to seas with normal oceanic salinity. The range

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... for survival and reproduction is 27 to 44 9~ S. Sipuncula are mainly deposit feeders. According to the mode of feeding and motility, the Sipuncula comprise 4 ecological groups: (1) burrowers, indiscriminately swallowing the substratum; (2) worms hiding in vacant shelters and collecting detritus; (3) waiting sestonophages; (4) sessile worms, scraping off food from the substratum.