Macrodasyida

Article By:

Hummon, William D. Department of Zoological and Biomedical Sciences, Ohio University, Athens, Ohio.

Last reviewed:August 2020

DOI:https://doi.org/10.1036/1097-8542.395600

An order of the phylum Gastrotricha. Members all have pharyngeal lumina that are inverted-Y–shaped, and most have pharyngeal pores. They inhabit marine or brackish waters, seldom freshwaters. Some do not exceed 0.5 mm (0.02 in.) in length, and most are not more than 1–1.5 mm (0.04–0.06 in.); these live in clean to detritus-rich marine sands of littoral or sublittoral areas. Both Dolichodasys, which reaches 2.5 mm (0.1 in.), and Megadasys, which reaches 4 mm (0.16 in.), inhabit black sulfide zones beneath quiet waters. All have front and rear groups of adhesive tubes; most also have tubes along their sides. Some have cuticular thickenings (Lepidodasys in one family) or scales or hooks (Acanthodasys, Diplodasys, Tetranchyroderma, and Thaumastoderma in another family). Macrodasys has a pointed rear; Urodasys has a tail (illus.a). Dactylopodolids, planodasyids, and turbanellids all have bilobed rear ends; lepidodasyids have rounded ones. Turbanella (illus.b) and Tetranchyroderma are the most common and most abundant of macrodasyids, with numbers of 50–100 per cubic centimeter of sand (800–1600 per cubic inch) not being unusual. See also: Gastrotricha

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