Characteristics of spermatozoa from five gall-midge species (Diptera, Cecidomyiidae)

The gall-midge family Cecidomyiidae is one of the largest within the animal kingdom. Its characteristics include, among others, a chromosome elimination during spermiogenesis and a bewildering diversity in sperm ultrastructure. The sperm tail, in particular, is unusual in that it deviates from the conventional 9+2 pattern of microtubules. We describe here the spermatozoa of five gall-midge species, all belonging to the same supertribe Cecidomyiidi. In Bremia more than 100 microtubular doubters form a tight spiral around a central mitochondrion. In an undetermined binomen many doublers form a spiral around the mitochondria in the distal end of the sperm tail, but a single row along a peripheral cistern in the main part of the tail. In Coquillettomyia caricis a peripheral row of doublets resides in the proximal part and tightly packed doublets distally. In Arthrocnodax sp. the many doublets also form a peripheral single or double row around a central mitochondrion. In Massalongia brachmaieri there are more than 500 doublets which form several rows around the nucleus and tightly packed doublers distally. The nuclear membrane forms bundles of extensive outpocketings. There is no acrosome. The nucleus consists of both condensed and dispersed material. Only outer dynein arms are present in all this species and the spermatozoa are motile. Cecidomyiidi species that have been examined for sperm structure fall into two groups: those where the mitochondria are confined to the centre of the tail and those in which the mitochondria lie in the head region and have a peripheral location. Most species belong to the first group, while Massalongia belongs to the second one. (C) 1997 Published by Elsevier Science Ltd on behalf of the Royal Swedish Academy of Sciences.