Histochemical Localization of Succinic Dehydrogenase Activity in the Mitochondria of some Invertebrate Spermatozoa

Abstract

THE mitochondria almost invariably form an essential component of the motile spermatozoa in the invertebrate¹. The possible exceptions, such as the spermatozoon of dragon fly², need re-investigation in the light of fresh reports on Lepisma^3,4. The mitochondria form a sheath around the axial filament, covering varying lengths of the flagellate spermatozoon, normally behind the nucleus; the anterior end of the nucleus being occupied by the acrosome. Exceptions to this rule are certain forms reported to have atypical spermatozoa¹; the most commonly cited examples being the spermatozoa of Lepisma^1,3–5 and Cicindela^5,6. In both these cases the centrosome moves forward to the anterior end of the nucleus dragging with it the axial filament having an extension of the mitochondrial sheath. In Lepisma the polarity of the nucleus is completely reversed, consequently the acrosome remains in the neck region and the centrosome heads the spermatozoon. These observations on the atypical flagellate spermatozoa have often been questioned as exemplified by a recent controversy on thysonuran spermatozoa^4,7–10.