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Journal of Experimental Biology 136,451-459 (1988)
Published by Company of Biologists 1988

Cephalic Neuroendocrine Regulation of Integumentary Water Loss in the Cockroach Periplaneta Americana L

JOHN NOBLE-NESBITT ¹ and MARWAN AL-SHUKUR ²

¹ School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ
² School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ; Department of Biology, College of Education, University of Baghdad, Iraq

Our experiments show that the brain of cockroaches produces, stores (temporarily or otherwise) and releases a water-loss promoting factor (BHP) and a waterloss restricting factor (BHR), depending on the physiological state of the cockroach and environmental conditions.

Fully hydrated cockroaches produce, temporarily store and release the BHP factor, and store but do not release the BHR factor: this leads to high rates of integumentary water loss.

Desiccation arrests the production and storage of BHP factor and stimulates the release of BHR factor, resulting in rapid restriction of integumentary water loss.

Brain homogenates prepared from fully hydrated cockroaches (HBH) contain some BHP factor and much BHR factor, whereas brain homogenates prepared from predesiccated cockroaches (DBH) contain only BHR factor.

Control saline-only injections produce only slight elevations in water loss of either fully hydrated or predesiccated intact cockroaches.

Lowering of integumentary water loss of intact fully hydrated cockroaches (HI) in response to desiccation is little affected by either HBH or DBH injection.

Conversely, injection of HBH into intact predesiccated cockroaches (DI) causes a highly significant increase in water loss during continued desiccation, confirming the presence of BHP factor in HBH.

DBH injection into DI cockroaches has little or no effect, presumably since it adds only BHR factor which is already present and active in the host.

Injected restricting factor (BHR) seems to be more effective than injected promoting factor (BHP) in decapitated cockroaches. Thus, considerably lower losses are found in decapitated fully hydrated cockroaches (HD) following HBH injection (Treherne & Willmer, 1975 and confirmed by us) or DBH injection (present results). Slightly elevated losses are found in decapitated predesiccated cockroaches (DD) following HBH injection, whereas DBH injection has little effect.

Key words: Periplaneta, cuticle, desiccation, water loss, hormonal control, decapitation, neuroendocrine

Accepted on January 4, 1988

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