Ergastoplasmic paracrystalline inclusion bodies in the adipose gonadal envelope and fat body of the glow worm, Lampyris noctiluca (Insecta, Coleoptera).

The gonads of glow worm larvae are enveloped by adipose tissue which represents a specialized fat body. The adipose gonadal envelope, and also to a lesser extent the fat body cells, contain tubular paracrystalline inclusion bodies (PIBs). Cells of other tissues are devoid of such inclusions. The PIBs form in the cisternae of rough ER. In young larvae PIB formation is sparse, but at advanced larval stages PIBs often occur as bundles in stacks of ergastoplasm. Typically, a PIB within a cisterna consists of four to seven parallel tubules. The outer diameter of a tubule is ca 28.8 nm and the width of the tubule lumen ca 12.2 nm. The "wall" of a tubule contains globular protein subunits of ca 8.3 nm diameter; the subunits are arranged helically. Since the adipose gonadal envelope progresses through a cytological differentiation process during differentiation and maturation of the gonads, the increased number of PIBs may indicate enhanced metabolic activity of the tissue related to nutrition of the growing gonads.