Ultrastructural aspects of spermatogenesis in Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955 (Monogenea; Microcotylidae).

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.

Report of Balanorchis anastrophus in Pará State with surface topography by scanning electron microscopy.

Balanorchis anastrophus Fischoeder, 1901, from the reticulum of Bos taurus is reported for the first time in the State of Pará, Brazil. The surface topography as revealed by scanning electron microscopy is presented.