Leptodactylus sperm

Valchi, Paula, Ponssa, María Laura, Farías, Alejandro, Volonteri, María Clara & Hermida, Gladys N., 2023, Comparative spermatozoa ultrastructure of neotropical grass frogs (genus Leptodactylus) with comments on anuran reproductive modes and phylogeny, Zoologischer Anzeiger 302, pp. 166-185 : 168

3.1. The general structure of Leptodactylus sperm

The acrosome covers the anterior portion of the head and consists of a single structure, the acrosomal vesicle ( Fig. 1A and B ). The acrosomal vesicle has the appearance of a conical cap, with homogeneous and moderate electron-dense material, extending from the tip of the cell to the anterior region of the nucleus. The acrosomal vesicle is symmetrically attached to the nucleus and ends in a bulb-shaped thickening ( Fig. 1A and B ). A sub-acrosomal space can be identified between the acrosomal vesicle and the nucleus. The nucleus is conical, since its diameter increases throughout its length, to a maximum at its base. In cross-sections it is circular and has electron-dense condensed chromatin. The nucleus is homogeneous with occasional small nuclear inclusions, also known as nuclear lacunae, observed as electron-lucent or electronpale material ( Fig. 1A and B ). Cytoplasm with mitochondria is observed surrounding the middle and posterior region of the nucleus ( Fig. 1B ). However, some cells lack a conspicuous cytoplasm with mitochondria in this region. In the latter, an organelle-free cytoplasmic region is observed as shown in Fig. 1A . This characteristic defines the two types of spermatozoa.

Figures

Fig. 1. A-B: Schematic reconstruction of the morphology of the two types of spermatozoa observed in the genus Leptodactylus. Note that the main difference between the two morpho-types is the presence of the organelle-free cytoplasmic region between the acrosomal vesicle and the other end of the nucleus. Dashed lines indicate the cross-section represented on the right-hand side of the image.