The spermatozoon of Arthropoda. 20. Structure and function in the spermatozoon of Tenebrio molitor

The spermatozoon of Tenebrio molitor is one of the most regular models to be found in insects. Its morphological characteristics are the following: a 3 layered acrosome; mitochondrial derivatives partially invaded by crystalline proteic material, with cytochrome oxidase activity present in the cortical zone where cristae persist; an axoneme with the classical 9+9+2 structure (of special interest is the eccentric initial region shaped like the mouth of a flute, rich in ATPase); and the presence of 2 UTPase and ATPase rich accessory bodies, rising from the Golgi complex. The tridimensional movement of the sperm is realized through 2 types of helicoidal waves of different amplitude and frequency, originating in the zone that links the nucleus with the flagellum. Both small and large waves are generated by the torsion of the particular asymmetrical structure located at the beginning of the axoneme, and spread all throughout the tail. The large wave maintains the constancy of its parameters thanks to the accessory motor formed by the UTPase and ATPase rich accessory bodies. The sense of the spreading waves is determined by the position of the larger mitochondrial derivative in the neck region.