Embryogenesis of the Sand Fly Phlebotomus papatasi (Diptera: Psychodidae): Organogenesis including Segmentation, Blastokinesis, Mouthparts, and Alimentary Canal

Abstract

The embryo of the sand fly Phlebotomus papatasi (Scopoli) consists of 17 units (the blastocephalon, 3 gnathal units, 3 thoracic, and 10 abdominal units) within the first 96 h of development. Shortening of the germ band starts at 108 h, and by 132 h it is completely withdrawn onto the ventral side of the egg. Anterior migration of the mouthparts is also associated with germ band movement. Formation of the labrum starts at 96 h, and by 120 h it appears as a distinct lobe. Antennal rudiments are evident at 96 h. Mandibles and maxillae are recognizable by 108 h, and a labium can be seen at 120 h. Blastokinesis occurs between 120 and 132 h. Stomodeal and proctodeal invaginations are observed at 84 h as infoldings of the blastocephalon and the terminal segment, respectively. The stomodeum differentiates into the preoral cavity, diverticulum, pharynx, and esophagus between 120 and 144 h and forms the proventriculus by 168 h. Development of the proctodeum begins at 120 h, and the pyloric ampulla, the ileum, and the colon are discernible at 168 h. Cells at the tip of the stomodeal-anterior midgut and the proctodeal-posterior midgut invaginate to form the midgut proper, which appears as a closed tube by 156 h. The gastric caecae originate from the midgut at its junction with the foregut by 180 h. The malpighian tubules arise from the anterior end of the proctodeum between 132 and 156 h. Anal papillae arise from the posterior end of the proctodeum at 168 h.