Neuroarchitecture of the clock system in the brain of Rhodnius prolixus adults and its association with neurosecretory cells
XANTHE VAFOPOULOU
Biology Department, York University, Toronto
We have shown that release of various hormonal neuropeptides from the brain of the insect Rhodnius prolixus is under circadian control, indicating their control by a clock in the brain. Previously, only behavioral rhythms were known to be controlled by insect brain clocks. Here, we describe the neuroarchitecture of the circadian system in the brain of adult Rhodnius and its association with neuroendocrine neurons. We used fluorescence immunohistochemistry for the neuropeptide pigment dispersing factor (PDF), a clock neuron marker, and confocal laser scanning microscopy to trace the axons of clock neurons through the brain. Compared with the larval stage, there are increases in the number of lateral clock neurons (LNs) and many new PDF-positive neurons appear which make contacts with these LNs, creating an extensive and elaborate network of PDF-positive axons potentially conveying rhythmicity throughout the entire dorsal protocerebrum. Crucially, LN axons make intimate contacts with the axons of various neuroendocrine cells, notably those of prothoracicotropic hormone in the lateral protocerebrum and bombyxin and LTE (Lymantrea Testis Ecdysiotropin) neurons in the medial protocerebrum, all of which are rhythmically released. We conclude the clock system controls rhythmic hormone release in a manner comparable to the mammalian suprachiasmatic nuclei.
Modulation of anoxic coma in locusts by the nitric oxide signaling pathway: A mechanism for regulating recovery from flash floods?
GARY A.B. ARMSTRONG and R. MELDRUM ROBERTSON
Department of Biology, Queen's University, Kingston ON
pending