Interstrain variation in larval respiration rate in Callosobruchus maculatus

摘要

Variation among strains of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in several life-history traits is well known. Differential respiration rates in larvae of this pest species may provide insights into how the behavioural process of larval competition within a seed produces different outcomes. Therefore, larval respiration rates in five strains of C. maculatus (from Brazil, Nigeria, South India, Uganda and Yemen) were measured during their early development. Per capita consumption of cowpea seeds by larvae of the same five strains was also carried out in another bioassay. The Brazil strain is reported as having a scramble-type of outcome of larval competition and it showed the smallest respiration rate of all five strains (6.13 ml O_2/day/larva), while the strains from Uganda and Nigeria that also resemble more closely the scramble-type of competition outcome showed intermediate levels of respiration rate (7.24 and 7.34 ml O_2/day/larva respectively). In contrast, the Yemen and SouthIndia strains are reported as having a contest-type of outcome of larval competition, although the behavioural process has been determined as contest only for the South India strain. The Yemen strain of C. maculatus showed the highest larval respirationrate, which did not significantly differ from the South India strain (8.39 and 7.49 ml O_2/day/larva respectively). Larvae from Yemen and South India strains also showed significantly higher per capita consumption rates of cowpea (15.15 and 11.31 mg respectively) than in larvae from the other strains (varying from 15.15 to 7.67 mg). This provides support for the hypothesis that the differential feeding rate is an important component of the larval competition outcomes observed in strains of C. maculatus