Differences in the morphology of prothoracic and propodeal spiracles in three strains of Apis mellifera: possible relation to resistance against Acarapis woodi

Abstract

SUMMARYThe prothoracic and propodeal spiracles of three honey bee strains used commercially in Greece (from N Greece, N Italy and Slovenia) were examined with a light microscope in order to detect possible morphological differences between the strains. This is an attempt to explain the apparent resistance against Acarapis woodi shown by the Greek Macedonian (N Greece) strain but not by the others. The propodeal spiracles of honey bees from N Greece and N Italy were examined, in addition, using a scanning electron microscope. Certain dimensions, like the length and the area of aperture in the prothoracic spiracle, were found to be significantly larger in honey bees from N Italy and Slovenia compared with the honey bees from N Greece. The length of aperture was found to be 648 μm in the honey bees from N Greece, while it was 13% larger in the honey bees from N Italy and 10% larger in the honey bees from Slovenia; the area of the aperture was found to be 103000 μm2 in the honey bees from N Greece, while it was 26% larger in the honey bees from N Italy and 27% larger in the honey bees from Slovenia. The dimensions of the propodeal spiracle were found to be similar between the strains examined. The fact that the prothoracic spiracle of honey bees from N Greece was significantly smaller compared to other honey bee groups (from N Italy and Slovenia), is discussed as a possible mechanism for resistance developed by this strain against Acarapis woodi.