University of Lethbridge, Alberta - May 8 to 11, 2002

R. GARY CHIANG & J.A. VAN STRATEN
Department of Biology, Redeemer University College, Ancaster, ON.

Exposure to low levels of juvenile hormone during metamorphosis affects egg production in the adult of the blood feeding insect, Rhodnius prolixus

Low doses of juvenile hormone (JH) administered topically to females in the penultimate larval stage (L5), after the onset of moulting and metamorphosis into the adult, created adult females displaying a few juvenile plaques located on the abdominal cuticle. In most other respects, these L5 females metamorphosed into adults with wings, reproductive organs, and abdominal lateral pleats. However, as adults, these females did not behave normally. Compared to normal unmated animals, they ingested twice the amount of blood when offered a blood meal, and during the egg production cycle triggered by the blood meal, 80% made significantly more eggs. Furthermore, their ability to lay these eggs was impaired. These results could be explained by JH interfering with the metamorphosis of structures associated with the cuticle.

L. SCULLY & R. GARY CHIANG
Department of Biology, Redeemer University College, Ancaster, ON.

Effect of severing the dorsal vessel on molting in Rhodnius prolixus.

The dorsal vessel was transected in L5 R. prolixus and the subsequent effect on the molting process was examined. Of the male and female insects whose dorsal vessels were severed, 32 of 33 (96%) were unable to manufacture new cuticles, while only 5 of the 19 (26%) sham controls failed to do so.   In addition, the insects with transected dorsal vessels that failed to molt ingested significantly smaller blood meals than the sham controls that formed new cuticles.   The results are discussed concerning the possibilities that either the smaller blood meals were the cause of the inability of those with severed dorsal vessels to form new cuticles or that transecting the dorsal vessels may have disrupted some neural or endocrine pathway vital to the molting process.

 

Laurentian University, Sudbury, Ontario - May 9 to 12, 2001

JENNIFER A. CHIANG & R. GARY CHIANG
Department of Biology, Redeemer University College, Ancaster, ON.

Removal of the anterior portion of the head mimics decapitation in the blood-feeding insect, Rhodnius prolixus

The head critical period (HCP) of Rhodnius denotes the length of time after feeding that a larva requires its head for moulting.   This period can be explained by the release of a brain hormone (prothoracicotropin, PTTH) which activates the production of ecdysone by the prothoracic gland.   We report that removing the anterior region of the head (the “nose”) prior to the HCP also prevents moulting in a significant number of animals.   To help determine why this operation mimics decapitation, we examined the effects of tying the “nose” from the rest of the animal before its removal.   In animals tied before cutting, females were not affected as much as the males.   These results suggest that factors which trigger PTTH release are influenced by other factors monitoring the physical state of the animal.

R. GARY CHIANG
Department of Biology, Redeemer University College, Ancaster, ON.

The effects of juvenile hormone III on fecundity in the blood-feeding insect, Rhodnius prolixus.

Several studies have shown that the application of exogenous juvenile hormone (JH) to adult Rhodnius reestablishes normal levels of egg production following experimental manipulations which reduce fecundity.   These studies provide experimental evidence that the adult CA activates egg production by releasing JH.   They also imply that the application of JH could be used in experimental protocols to gain further insights into the role of the CA in reproduction.   However, the JH used in earlier experiments (JHI) is no longer commercially available.   This study reports that the effects of a commercially available JH (JHIII) mimic those of JHI.   Thus, JHIII could be used to study egg production in Rhodnius when JHI is not available.

 

University of Ottawa, Ontario - May 5 to 8, 1999

R. GARY CHIANG
Department of Biology, Redeemer University College, Ancaster, ON.

An investigation of neural inhibition of the corpus allatum in larvae of the blood-feeding insect, Rhodnius prolixus..