FUNCTIONAL MORPHOLOGY OF THE FOREGUT OF CHONOPELTIS AUSTRALIS BOXSHALL (BRANCHIURA)

The morphology of the foregut of the ectoparastic branchiuran Chonopeltis australis is described from serial transverse, longitudinal, and frontal sections of whole parasites and from SEM micrographs. The foregut is differentiated into four histomorphological regions: a preoral cavity, housed inside the proboscis and containing the tongue and mandibles; an ascending esophagus supplied with constrictor, longitudinal, and dilator muscles; a horizontal esophagus supplied with constrictor muscles only; and an esophageal funnel, containing cuticle-lined inner and recurrent walls, reminiscent of the cardia of muscoid flies. The mandibles apparently do not function as lacerating organs, but instead cram mucus and cellular detritus into the preoral cavity. Five dentigerous plates, guarding the oral aperture, function as a filter during feeding. The muscle complex in the walls of the ascending esophagus facilitates movement of aliment through the foregut into the anterior midgut. The comparative morphology and functional significance of each part of the foregut are discussed.