Importance of temperature and seed water content on the induction of imaginal polymorphism in Callosobruchus maculatus
1991
Ouedraogo, P.A. | Monge, J.P. | Huignard, J.
Callosobruchus maculatus (F.) is a tropical insect (Coleoptera: Bruchidae) that develops in Vigna unguiculata (Walp) seeds. In this beetle, there are two distinct adult forms that differ in their morphology, physiology and behaviour, the flight form and the flightless form. The development of C. maculatus is analyzed in a traditional store in Niger. During the dry season, 6 to 7 generations of the flightless form develop in the store. When the atmospheric water content increases during the rainy season, adults of the flight form appear and escape from the store. Experimental studies have shown that the adult polymorphism is induced during post-embryonic development and depends on prevailing abiotic factors during this period. The proportion of flight from adults is high when larvae develop in moist seeds (14-15% of water content). Under dry conditions (6-7% of water content) only flightless adult forms emerge from the seeds. Temperatures during development also influence adult polymorphism. In thermoperiodic conditions with 12-13% seed water content, the proportion of flight from adults increases with increasing duration of the thermophase. However, at low temperatures, a high proportion of flightless adult forms emerge, regardless of seed water content. The adaptive importance of these two abiotic factors on polymorphism induction is examined in this study.
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