Hormonal control of salivary gland degeneration in the ixodid tick Amblyomma hebraeum

Under normal circumstances, salivary glands of female ixodid ticks begin degenerating within hours of completing the blood meal. We have monitored cytological, functional and biochemical changes in the tissue which are diagnostic of the degenerative process. Although ultimately degeneration also befalls salivary glands of partially fed ticks removed prematurely from the host, the process is considerably delayed. When we transplanted salivary glands from partially fed ticks into the haemocoels of replete specimens, autolysis was induced in the donor tissue, whereas such was not the case when similar glands were transplanted to the haemocoels of other partially fed ticks. We thus suggest that a humoral factor is involved in postprandial resorption of the salivary glands. Succinate dehydrogenase activity decreases, and acid phosphatase activity increases in the salivary glands as a function of time post-engorgement. However, these enzyme assays are not sensitive enough to detect the earliest stages of autolysis.