Chromosome studies in North-Western Sicily males of Rhynchophorus ferrugineus

Rhynchophorus ferrugineus (Olivier), known as red palm weevil (RPW) was accidentally introduced and established in Sicily (Italy) since 2005. As like in other Mediterranean sites, RPW has been causing extensive damage to palm trees and on its new host Phoenix canariensis Chabaud (Canary Island palms), acquired concomitantly with the colonization of the area. RPW shows a good ecological plasticity and slightly but significant morphological polymorphism (colour patterns and length of the rostrum in male individuals) that can be appreciated within different geographical populations. The aim of the present work was to investigate if this ecological plasticity and phenotypic variability can be accompanied by features in chromosomes like changes in diploid number or chromosome morphology, when compared to other RPW populations. Literature data on karyotype analysis reveals a diploid number (2n = 22). In this paper, the karyotypes of different morphotypes of RPW Sicilian populations, collected from P. canariensis, were analysed using conventional staining, C-banding and sequential staining with the fluorochromes chromomycin-A3/4-6-diamidino-2-phenylindole (CMA3/DAPI). The analyses of metaphases obtained from the testes of adults showed that the species has 2n = 22 chromosomes, with 10 autosomal pairs and a sex chromosome pair. The eu-heterochromatic composition investigated with CTG banding, DAPI, CMA3, and NOR do not indicate any peculiarity in the populations investigated. R. ferrugineus has a Coleoptera Curculionoidea chromosomal asset and functional compartimentalization. RPW presents a karyotype with intermediate characteristics between Dryophthorinae and Curculioninae such as micro Y chromosome and the typical “sphere-shape” of the sexual bivalent in prophase-I or after C-banding.