Macro- and microscopic ovarian features of Hemiodus microlepis, H. ternetzi and H. unimaculatus were analyzed. Based on these features we proposed an ovarian maturation scale. The nine stages of the preliminary macroscopic fieldwork scale were reduced to five after microscopic analysis of ovaries. The microscopic analysis indicated a group-synchronous oocyte development common to the three species that were characterized as iteroparous synchronous spawners with a total spawning type. The remarkable thickness of the zona radiata layer and the large size of vitellogenic oocytes of Hemiodus ternetzi distinguished this species from the others.
Hemiodontid; oocyte development; zona radiata; fish reproduction; Tocantins River