Fig. 1

Ovary at the RUD stage under light microscopy; a–f sections stained with hematoxylin and eosin (HE); g xylidine ponceau stain; h PAS stain; i Alcian blue stain; a, b Mithrax tortugae (Rathbun, 1920). a Ovarian structure enveloped by a thick layer of connective tissue. Note the oocytes surrounded by follicular cells (black arrow) arranged in the periphery with a central germinal zone; b oogonia with nucleus occupying a large part of the cells and basophilic cytoplasm, nuclei with meiotic prophase (black arrow); c Mithraculus forceps A. Milne-Edwards, 1875, proliferation of oogonia and presence of follicular cells around the oocytes; d, e Omalacantha bicornuta (Latreille, 1825) and Mithraculus forceps, presence of lucid vesicles (white arrows) and vesicles with acidophilic material (black arrow) in the cytoplasm of oocytes; f Mithrax hispidus (Herbst, 1790), increase in oocyte size from the germinal zone (black arrow) towards the periphery (white arrow); g, h Mithrax tortugae andMithraculus forceps, cytoplasm and endogenous yolk vesicles with positive reactivity for proteins and neutral polysaccharides; i Mithrax hispidus, cytoplasm and endogenous yolk vesicles with the absence of acid polysaccharides. Note the presence of endogenous yolk vesicles (white arrows) and lucid vesicles (black arrows) in the oocytes. CT connective tissue, FC follicular cell, GZ germinal zone, N nucleus, NU nucleolus; OC oocyte, OO Oogonia