O ácaro Varroa destructor e as abelhas africanizadas: uma abordagem morfométrica da relação entre parasito e hospedeiro

Abstract

The Varroa destructor mite, a significant parasite of Apis mellifera bees, is subjected to a range of environmental pressures, encompassing climatic conditions and host defenses, such as hygienic behavior. Morphological analysis enables the quantification of morphological variations within and among populations, facilitating the inference of their underlying causes. Additionally, assessing fluctuating asymmetry measures the degree of stress encountered during organism development. The evaluation of these two parameters in mites can contribute to a comprehensive understanding of their adaptive strategies. The objectives of the present study were (1) to identify anatomical structures that more precisely capture morphological variations and fluctuating asymmetry in V. destructor; (2) to assess the relationship between the level of hygienic behavior in Africanized bee colonies (A. mellifera) and the morphology of V. destructor, as well as the correlation between fluctuating asymmetry in the host and parasite across different colony types. Mites and Africanized bees were collected from colonies exhibiting varying degrees of hygienic behavior in apiaries located in the Atlantic Forest and Caatinga regions. The analysis of bees involved the examination of their front wings, while mites were scrutinized based on their ventral shields, specifically the metapodal shields and genito-ventral shield. In the first chapter, V. destructor shields were identified that most accurately reflect variations in shape (crossvalidation discriminant analysis) and size (t-test) and the fluctuating asymmetry of shape and size (Procrustes ANOVA and t-test). The pair of mite metapodal shields presented the highest group classification rates, based on shape, by cross-validation, between locations (78%) and types of host colony (70%). Among colony types, it was the only one that showed differences in size between groups (p<0.001). It was also the only shield that allowed the analysis of fluctuating asymmetry of shape and size. The plate seems more suitable to reflect morphological differentiation and fluctuating asymmetry, and is recommended as a standard structure for future research. In the second chapter, we investigated the relationship between the level of hygienic behavior in bee colonies and the morphology of V. destructor mites, as well as the connection between fluctuating asymmetry in the host and parasite across different colony types. Notably, significant differences were observed in both the shape (p<0.001) and size (p<0.001) of mites infesting different colony types, particularly in the metapodal shield. Mites from hygienic colonies exhibited smaller sizes, suggesting distinct developmental pressures experienced by the two parasite groups. Moreover, variations were identified in the fluctuating asymmetry of both bee (p<0.01) and mite (p<0.01) structures. An inverse correlation was observed in the fluctuating asymmetry of size between host and parasite structures; bees from hygienic colonies exhibited higher rates of fluctuating asymmetry, while their associated mites demonstrated lower levels. These findings indicate that factors beyond hygienic behavior may exert a more significant influence on fluctuating asymmetry within the host-parasite relationship.