Morphology and ultrastructure of the Balbiani body in the oocytes of closely related bush cricket species. Shared features reveal important aspect of functioning

Abstract

Balbiani bodies (Bbs) are female germline-specific organelle assemblages usually composed of mitochondria, Golgi complexes, elements of endoplasmic reticulum and accumulations of fine granular material, termed the nuage. Here we present results of morphological and ultrastructural analysis of the Bb of four bush crickets nested in four subfamilies of the family Tettigonidae. This study has revealed that Bbs of closely related species (belonging to the defined evolutionary line) are morphologically rather different. In two species (Meconema meridionale and Pholidoptera griseoaptera) the Bb has the form of a hollow hemisphere that covers a part of the germinal vesicle surface. In contrast, the Bb of Conocephalus fuscus and Leptophyes albovittata is less distinct and surrounds the whole or the majority of the germinal vesicle surface. Aside from this difference, the Bbs of all four studied species are built of identical sets of organelles and, most importantly, share one significant feature: close association of mitochondria and nuage accumulations. We show additionally that mitochondria remaining in direct contact with the nuage are characterized by distinct morphologies e.g. elongated, dumbbell shaped or bifurcated. In the light of our results and literature survey, the ancestral function of the Bb is discussed.