Ultraviolet-induced histological and histochemical changes in the integument of newly molted American cockroaches, Periplaneta americana (Dictyoptera: Blattaria: Blattidae)

Abstract

Hypodermal cells of newly molted cockroaches irradiated with UV (254 nm) are progressively destroyed, with first evidence of structural damage occurring 2 h after initiation of irradiation. Before that, melanin formation begins to fall and irradiated animals become progressively more deficient in melanins or their precursors. Proteins of the exocuticle fail to tan in irradiated cuticle, as indicated by continued uptake of protein stain at a time when unexposed cuticle becomes refractive to staining. Hypodermal cells are irreversibly damaged by UV irradiation, as evidenced by lack of endocuticle production. Similarly, tonofibrillae are progressively destroyed in tergal attachments of tergostemal muscles exposed to UV. Muscles become detached, possibly in the legs as well, resulting in sluggish behavior. With tanning incomplete and hypodermal cells destroyed, the integument ceases to become an effective barrier to dehydration, and molting failure or death, due to desiccation, may result.