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The Journal of Experimental Biology 205, 3123-3131 (2002)
Copyright © 2002 The Company of Biologists Limited

Enhanced haemolymph circulation by insect ventral nerve cord: hormonal control by Pseudaletia unipuncta allatotropin and serotonin

P. M. Koladich¹, S. S. Tobe^1,* and J. N. McNeil²

¹ Department of Zoology, University of Toronto, Toronto, Ontario, M5S 3G5 Canada
² Department of Biology, Laval University, Sainte-Foy, Quebec, G1K 7P4 Canada

^* Author for correspondence (e-mail: stephen.tobe{at}utoronto.ca)

Accepted 17 July 2002

The ventral diaphragm (VD) in many insects is a muscular membrane that essentially partitions a perineural sinus from the rest of the abdomen. In the true armyworm moth Pseudaletia unipuncta (Lepidoptera: Noctuidae) we describe how the VD is characterized by a series of aliform muscles inserted into a tissue matrix that is fused to the dorsal surface of the ventral nerve cord (VNC) itself. Because of this arrangement, the abdominal VNC can attain high rates of lateral oscillation, and is capable of directing haemolymph flow. We have previously demonstrated Manduca sexta allatotropin (Manse-AT)-like immunoreactivity throughout the central nervous system (CNS) in P. unipuncta, and that both Manse-AT and serotonin (5-HT) are dose-dependent stimulators of the dorsal vessel. Here we describe both Manse-AT- and 5-HT-like immunoreactivity associated with the VD. Furthermore, both Manse-AT and 5-HT are dose-dependent stimulators of the rates of VNC oscillation, and together are capable of maintaining highly elevated rates of VNC oscillation for extended periods of time. These data indicate that both the dorsal vessel and the VD/VNC are similarly modulated by both Manse-AT and 5-HT, and that VNC oscillations play a more active role in overall haemolymph circulation than previously recognized.

Key words: allatotropin, haemolymph circulation, Manduca sexta, Pseudaletia unipuncta, serotonin, ventral diaphragm, ventral nerve cord