ReviewBalbiani body, nuage and sponge bodies - The germ plasm pathway players

•Morphology and composition of arthropod Balbiani bodies is reviewed.•In most species the Balbiani body consists of mitochondria and nuage accumulations.•Arthropod Balbiani body participates in the localization of germ plasm components.•In some derived spiders the Balbiani body is a site of lipid droplet formation.

In many animal species, germ cells are specified by maternally provided, often asymmetrically localized germ cell determinant, termed the germ plasm. It has been shown that in model organisms such as Xenopus laevis, Danio rerio and Drosophila melanogaster germ plasm components (various proteins, mRNAs and mitochondria) are delivered to the proper position within the egg cell by germline specific organelles, i.e. Balbiani bodies, nuage accumulations and/or sponge bodies. In the present article, we review the current knowledge on morphology, molecular composition and functioning of these organelles in main lineages of arthropods and different ovary types on the backdrop of data derived from the studies of the model vertebrate species.