Cockroaches decapitated in a fully hydrated state at first lose water under desiccation much more rapidly than their intact counterparts. The rate of loss decreases with time of desiccation; this decrease is more marked in decapitated than in intact cockroaches.
The initial rate of water loss is lower and less variable in predesiccated cockroaches and continues to fall gradually during further desiccation. Decapitation of predesiccated cockroaches has little effect on the rate of water loss. Similarly, the rate of water loss is low with low variability in water-stressed cockroaches taken from dry culture conditions, and decapitation has no significant effect.
The lowering of the rate of water loss is not a simple response to lowering of the body water content, but is a two-stage, time-related physiological response of acclimatization to water-stress or desiccation. The initial phase of rapid response requires the presence of the head, whereas the subsequent gradual phase does not.
With the techniques used in this investigation, handling-related effects of the decapitation procedure are not significant.
Present address: Department of Biology, College of Education, University of Baghdad, Iraq.