The sperm structure and spermiogenesis of the heteropteran Coptosoma scutellatum (Geoffroy) with emphasis on the development of the centriole adjunct

• The sperm structure of the uncommon heteroptera Coptosoma scutellatum is described.
• During spermiogenesis an extensive centriole adjunct material is produced.
• Such a centriole adjunct is a MTOC (microtubule-organizing-center).
• In the mature sperm the centriole adjunct is transformed in a dense, compact material.

The sperm structure and spermiogenesis of the morphologically peculiar heteropteran Coptosoma scutellatum has been examined with electron microscopy. The sperm has a short monolayer acrosome, a cylindrical nucleus, a 9 + 9 + 2 axoneme and two mitochondrial derivatives with crystallized matrix. It shows the synapomorphies typical of the group, consisting of (a) two crystallized areas in the mitochondrial derivatives; (b) the presence of two bridges connecting the intertubular material of the flagellar axoneme to the flattened cisterns adhering to the inner sides of the mitochondrial derivatives; (c) the absence of accessory bodies. The most interesting feature is the presence, in the early spermatid, of an extended centriole adjunct material with the shape of a large ribbon-like structure. This material surrounds the posterior nuclear region and extends anteriorly along the nucleus. It is a microtubule-organizing-center (MTOC) producing the many microtubules surrounding the sperm components At the end of spermiogenesis, the centriole adjunct material modifies into two kidney-like structures accompanying the nuclear posterior end and surrounding the modified centriole.