Ultrastructural aspects of spermatogenesis, spermiogenesis and
of the mature spermatozoon of a microcotylid monogenean
Metamicrocotyla macracantha parasite from Mugil liza, are
described. The irregularly-shaped spermatogonia divides by
successive mitoses, forming the primary spermatocytes,
identified by the presence of synaptonemal complexes in their
nuclei. The spermatids formed by meiotic cell divisions of
the secondary spermatocytes, differentiate into a mature
spermatozoon. Cross sections of the head and the middle region
of mature spermatozoa show the nucleus with strong condensed
chromatin, the mitochondria with short cristae, peripheral
microtubules and two axonemes with a 9+1 pattern, confirming
the characteristics of this genus.
