|Bruno M D Tran||
. T&a, 1993
Selected publications - Tran & al, 1993
Journal of Insect Physiology
Changes in responsiveness to factors inducing diapause termination in Bruchus rufimanus (Boh.) (Coleoptera: Bruchidae)
B. Tran, J. Darquenne* and J. Huignard*
* Institut de Biocenotique des Afrosystèmes—URA CNRS 1298, Faculté des Sciences de Tours, Parc de Grandmont, 37200, Tours, France.
Received 7 December 1992; revised 15 February 1993. Available online 1 October 2003.
Bruchus rufimanus undergoes a reproductive diapause from the emergence of the adults, in September, until April, when the adults enter the fields of their plant host, at the beginning of the flowering period. In a previous paper, we pointed out that long days and the consumption of host plant pollen are the main environmental factors which are required for the termination of the diapause. We now analyse the modifications of ovariole structure and changes in the responsiveness of the bruchid to these environmental factors during the course of diapause. In constant conditions (10°C, constant darkness) in which diapause is maintained, the structure of the ovarioles does not vary during the first 5 months of diapause, but, after 6–7 months, previtellogenic phases are observed in the basal oöcytes. In September, a very small percentage of adults which have not experienced the exposure to 10°C, constant darkness, undergoes diapause termination when they are exposed to long days and consume pollen. The percentage of adults in which diapause terminates in conditions normally leading to termination increases after a period of 3–4 months in the diapausing conditions. We propose that horotelic processes take place during this initial phase of diapause. Longer periods in diapause do not result in greater rates of diapause termination when insects are exposed to long days and host plant pollen. The second phase of diapause, from the 5th month onwards, is interpreted as a facultative one, during which the insects are ready to respond to the factors inducing both the morphological and physiological development. The variations in responsiveness are important in the beetle's life history.
Author Keywords: Reproductive diapause; Diapause development; Diapause termination; Bruchids; Overwintering
12 March 2006