The Stoma

The mouth-like stoma is the anterior end of the digestive system. The opening of the stoma with a cuticular lining most closely associated with the body wall is the cheiolostom. The remainder of the stoma is either surrounded by the pharynx (stegostom) or not (gymnostom). The stoma may be a simple open cylindrical cavity (A, B), it may be modified with teeth (C) or a hypodermic-needle-like stylet (D, E) depending on the feeding style of a particular nematode as shown in the examples below. The needle-like stylet may developmentally be a modification of the stoma wall (D) or alternately it may be a modified tooth (odontostylet) associated with an elongate base under the tooth (odontophore) (E).

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Fig. 3. The stoma. A. Caenorhabditis elegans (Rhabditina) (dorsal). B. Zeldia punctata (Cephalobina) (dorsal) C. Aduncospiculum halicti (Diplogastrina) (left side dorsal, right side subventral). Note the large dorsal tooth. D. Heterodera glycines male (Tylenchina) (lateral). Note the needle-like stylet. E. Xiphinema sp. (lateral). Note the needle-like modified tooth (odontostylet) and elonagte base under the tooth (odontophore). A-C redrawn from Baldwin et al, 1997b, E redrawn from Coomans, 1963.