Ultrastructure of Silk Gland of Webspinners, Oligotoma japonica (Insecta, Embioptera)

Abstract

Certain Chelicerata and Hexapoda in the Arthropoda produce silk threads of a proteinaceous material which is insoluble in water. All glands producing silk are considered of ectodermal origin. Silk glands of chelicerates are primary epidermal invaginations, which often occur in several pairs differing in their kind of secretion, and the silk glands of most insects (labial glands) are derived secondarily from other types of glands. However, a characteristic feature of the Embioptera including lower Hexapoda is the retention of the silk glands in the tarsal segment of the front legs; these glands are considered derivatives from the hypodermis and are covered with bristles (Sefnal and Akai 1990). The silk webbing is employed in building silken tunnels which they inhabit. So far as the authors are aware, there are few papers concerning the structure of the spinning organ of the Embioptera (Melander 1903, Mukerji 1927, Alberti and Storch 1976, Nagashima et al. in press). As part of an ongoing study, the ultrastructure of the silk gland of the Japanese webspinner, Oligotoma japonica Okajima is described here in detail. Also touched on is the silk protein synthesis and intracellular transport. © 1991, Japan Mendel Society, International Society of Cytology. All rights reserved.