spacer gif spacer gif spacer gif spacer gif Online submission spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Smith, J. J.
Right arrow Articles by Lampert, G. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Smith, J. J.
Right arrow Articles by Lampert, G. J.

Journal of Experimental Biology, Vol 198, Issue 1 249-261, Copyright © 1995 by Company of Biologists

JOURNAL ARTICLES

An electrical model for Periplaneta americana pronotal integument: an epidermal location for hydration-dependent resistance

JJ Smith, J Machin and GJ Lampert
Department of Zoology, University of Toronto, Ontario, Canada.

Measurements of electrical resistance appear to be useful indicators of porosity and related water permeability in insect cuticle. To develop an adequate understanding of how such measurements relate to the physical and structural properties of the integument, we made detailed determinations of resistance and impedance values for pronotal cuticle in adult male Periplaneta americana. The most consistent estimates were obtained by averaging measurements across the integument on both sides of the midline at several intervals starting 15 min after electrode application. Pronotal resistance varied inversely with water content, from about 10 k omega cm2 in hydrated cockroaches to about 40 k omega cm2 in dehydrated insects. Though the dermal gland canals appear to act as the main conductive pathway across the cuticle, the variable 'barrier' is located in the epidermal layer, since removal of the epidermis from isolated pronota also removes most of the variable component of the integumental resistance. Comparison of measurements between two external electrodes with single-electrode measurements revealed a 'shunt' pathway parallel to the cuticle surface; modelling this shunt suggested that it was variable and located mostly internal to the cuticle, supporting an epidermal location for a variable barrier. Impedance measurements over a range of frequencies showed the integument to be electrically complex, and a model is proposed to account for its properties.




© The Company of Biologists Ltd 1995