Zoological Studies

Vol. 37 No. 2, 1998

Morphology and Ultrastructure of the Alimentary Canal of Oriental Fruit Fly Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) (I): The Structure of the Foregut and Cardia

Wen-Yung Lee*, Mei-Er Chen and Tai-Lang Lin

Institute of Zoology, Academia Sinica, Taipei, Taiwan 115

Wen-Yung Lee, Mei-Er Chen and Tai-Lang Lin (1998) The foregut and the cardia of Bactrocera dorsalis (Hendel) were investigated by light microscopy and transmission electron microscopy. The foregut of this fly is comprised of a tiny slender tube, the oesophagus, and a lateral diverticulum of the crop. The crop provides a long, smooth duct opening near the end of the oesophagus, and a sac located in the anterior part of the abdomen. The oesophagus and the crop have a thick cuticle (the intima), a thin and simple epithelium, a basement membrane and it is surrounded by a well-developed visceral circular muscle. The cardia is located between the foregut and the midgut, and includes the midgut epithelium in the outer portion of the cardia and the foregut epithelium in the inner portion. The oesophageal epithelium extends into the cardia to form the cardial valve. Both the longitudinal and the circular muscles beneath the oesophageal epithelium form a sphincter to control the entrance of food to the midgut and prevent the regurgitation of the midgut contents. The peritrophic membrane is secreted and forms from the surface of microvilli of the midgut at the anterior part of the cardia.

Key words: Oesophagus, Crop, Cuticle, Epithelium.

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