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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

View larger version (57K): [in a new window]   Fig. 1. Anatomy of the ventral nerve cord (VNC) and ventral diaphragm (VD) in adult male and female P. unipuncta. (A) Schematic representation of the abdomen (Ab), indicating the relative positioning of the VNC (blue) and VD (red) in dorsal view. Th, thorax. Note that due to scaling constraints, the VNC and VD are represented approximately twice as wide as they are in situ. (B) Colour representation of a transverse section through the adult abdomen, taken at the position of the dotted line in A. (C,D) Dorsal and lateral views of the VNC (blue-grey) and VD, comprising the collagen matrix (CM) and associated alary muscles (AM) (violet). AG, abdominal ganglia; FB, fat body; VC, cuticle. Scale bars, 1 mm (A); 100 µm (B—D).

View larger version (77K): [in a new window]   Fig. 2. (A—C) Time-lapse photo sequence of the oscillating ventral nerve cord (VNC) of adult P. unipuncta moths. The VNC was stained to enhance contrast with the surrounding fat body. (D—F) Outline of VNC from the panels A—C, respectively. The red lines indicate the ventral mid-line of the abdomen. Scale bar, 200 µm.

View larger version (50K): [in a new window]   Fig. 3. Time-lapse photo sequence of active movement of dye resultant from ventral nerve cord (VNC) oscillations in P. unipuncta adult moths. (A) Diagram of abdomen in dorsal view indicating the site of dye introduction in the anterior abdomen (arrow) and the region where the dye reappears in the posterior (double arrowheads). (B) Insertion of the syringe through the copious amounts of fat body at the site of injection (arrow). (C—F) Photographic sequence at 0.1 s intervals after injection showing the appearance of dye in the region of the posterior abdomen dorsal to the terminal abdominal ganglion.

View larger version (73K): [in a new window]   Fig. 4. Immunoreactivity (IR) associated with the ventral nerve cord (VNC) and ventral diaphragm (VD) of a day-3 adult P. unipuncta female. (A) Manse-AT-like immunoreactivity, dorsal view; (B) 5-HT-like immunoreactivity, lateral view. Whereas Manse-AT-like immunoreactive nerves run primarily on the dorsal surface of the collagen matrix (arrow), 5-HT-like immunoreactivity is seen primarily associated with nerves within the collagen matrix itself (double arrowheads). AM, alary muscles; CM, collagen matrix; TAG, terminal abdominal ganglia; VNC, ventral nerve cord. Scale bars, 100 µm.

View larger version (19K): [in a new window]   Fig. 5. The dose-responses of semi-isolated adult virgin day-3 male and female P. unipuncta ventral nerve cord (VNC) upon exposure to increasing concentrations of Manse-AT in saline. Data are expressed as percentage increase in the resting rate of oscillation and values are means ± S.E.M. (N=5 or more samples). *Significant increase from resting rate (P<0.05).

View larger version (19K): [in a new window]   Fig. 6. The dose-responses of semi-isolated adult P. unipuncta virgin day-3 male and female ventral nerve cord (VNC) upon exposure to increasing concentrations of 5-HT in saline. Data are expressed as percentage increase in the resting rate of oscillation and values are means ± S.E.M. (N=5 or more samples). *Significant increase from resting rate (P<0.05).

View larger version (23K): [in a new window]   Fig. 7. Temporal changes in the rate of oscillation of the ventral nerve cord (VNC) of P. unipuncta following application of Manse-AT or 5-HT in saline, independently or concurrently, at t=0 to semi-isolated VNC of adult virgin day-3 females at concentrations approximating their EC50 values. Data are expressed as percentage increase in the resting rate and values are means ± S.E.M. (N=5 or more samples). *Significant increase from resting rate (P<0.05).

View larger version (18K): [in a new window]   Fig. 8. Effects of repeated exposure of Manse-AT on the rate of oscillation of semi-isolated adult P. unipuncta virgin day-3 female VNC. Manse-AT was serially applied at approximately the EC50 value at 0, 2, 4 and 6 min. Data are expressed as percentage increase in resting rate and values are means ± S.E.M. (N=5 or more samples). *Significant increase from resting rate (P<0.05).