Cuticle secretion during larval growth in Drosophila melanogaster

• Published in: Journal of insect physiology Vol. 31; no. 10; pp. 801,811 - 809,813
• Main Authors: Kaznowski, Christine E., Schneiderman, Howard A., Bryant, Peter J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 1985; Elsevier
• Subjects: Biochemistry. Physiology. Immunology; Biological and medical sciences; Cuticle; Drosophila; Drosophila melanogaster; Drosophilidae; ecdysis; Fundamental and applied biological sciences. Psychology; growth; Insecta; Invertebrates; larvae; molting; Physiology. Development; Cuticle; growth; ecdysis; Drosophila; Transmission electron microscopy; Growth; Secretion; Ultrastructure; Arthropoda; Insecta; Invertebrata; Drosophila melanogaster; Diptera; Molt; Drosophilidae
• ISSN: 0022-1910; 1879-1611
• DOI: 10.1016/0022-1910(85)90073-3

The moulting cycle and growth of the larval integument of Drosophila melanogaster has been studied by light and electron microscopy. Growth during the first, second and third larval instars is accompanied by 3.0-, 3.4- and 3.7-fold increases in surface area, respectively. Growth in surface area occurs continuously during the larval stages, with no detectable relationship to the moulting cycle. Measurements of the thickness of the cuticular layers show that the endocuticle grows in thickness by apposition and in surface area by stretching. The pre-apolytic epicuticle remains at fairly constant thickness during the increase in surface area, indicating that it grows by intussusception of new components. Post-apolytic epicuticle becomes thinner and increases in surface area by stretching. The epicuticle and pre-ecdysial endocuticle are traversed by filaments, but these do not penetrate the endocuticle secreted after ecdysis. We suggest that the filaments transport breakdown products from the old cuticle inward to the epidermis for reutilization. The growth and deposition of cuticle in two larval growth mutants, lethal (2) giant larvae and Chubby Tubby, involves mechanisms similar to those found in wild-type larvae, but in Chubby Tubby the endocuticle contains inclusions which are ultrastructurally similar to dense epicuticle.