Visualization of polyfusomes in gonads of a moth,Ephestia kuehniella Z. (Lepidoptera : Pyralidae), by a microspreading technique and electron microscopy

Microspreads of gonads are usually employed to analyse the behaviour of the synaptonemal complexes during meiosis. We show in the present report that microspread preparations can be used for the study of polyfusomes as well. Polyfusomes are bridge systems which, as a result of incomplete cleavage, interconnect germ cells in both sexes of higher insects. In spread preparations using gonads of both sexes of a moth, Ephestia kuehniella (Lepidoptera : Pyralidae), the polyfusomes appear as threads of material of medium electron density. The threads are branched when later developmental stages are observed. Remnants of the electron-dense contractile rings are visible and signal the position of a preceding cleavage. The comparison of a branched spread polyfusome with the reconstruction of a fully differentiated serially sectioned polyfusome from a moth ovary, shows that spread preparations, while more rapid and less costly, visualize the bridge system properly. Polyfusomes interconnecting male germ cells show numerous ramifications. It appears difficult to preserve them in their full size in whole-mount preparations. Large polyfusomes probably fragment during the spreading procedure. Nevertheless, visualization of polyfusomes and associated contractile rings in spread preparations opens new inroads for the study of the composition and the behaviour of these components.