Symbiosis in the Dryophtoridae weevils (Coleoptera : Curculionoidea): morphological variability of symbiotic interacellular bacteria
Résumé
Dryophthoridae weevils are phytophagous insects thriving on a broad host-plant
spectrum. Some, such as Sitophilus spp. or Cosmopolites sordidus, are major
agricultural pests of cereals and bananas, respectively. Previous studies have
concluded that several Dryophthoridae species harbour intracellular bacteria
(endosymbionts) in specialized organs named bacteriomes. In this work, we have
demonstrated the presence of intracellular symbiosis in seven out of the eight
Dryophthoridae species tested, and have assessed the morphological variability of
these endosymbionts. Histological analyses of the endosymbionts in either the larval
bacteriome or adult female ovaries reveal two fields of variability: physiologic
(length variation during host development) and morphologic (both interspecific and
intraspecific). These variations are expressed to different degrees in the species
studied. Indeed, Sitophilus granarius displays much less pleiomorphism than
5. zeamais. Such pleiomorphism may be a consequence of both genetic polymorphism
and host/bacteria interaction.