Bryconamericus exodon, Eigenmann, 1907

Baicere-Silva, Clarianna Martins, Ferreira, Katiane M., Malabarba, Luiz R., Benine, Ricardo C. & Quagio-Grassiotto, Irani, 2011, Spermatic characteristics and sperm evolution on the subfamily Stevardiinae (Ostariophysi: Characiformes: Characidae), Neotropical Ichthyology 9 (2), pp. 377-392 : 381

Bryconamericus exodon ( Fig. 6 A-L)

In the spermatozoon of Bryconamericus exodon the ovoid nucleus measures 1.5  m in the longitudinal axis and 1.2  m in the transverse axis. The surrounding strip of cytoplasm has no organelles ( Fig. 6A ). Nuclear rotation toward the flagellar axis was about 80 degrees ( Fig. 6 A-B). The midpiece has a conical shape, measures about 1.17  m in length and contains some slightly elongate mitochondria ( Fig. 6 A-E).The endomembrane system is composed by vesicles with different sizes connected to clump of smaller vesicles with a lacy aspect ( Fig. 6 F-L).

system, composed of tubules and/or vesicles, is found throughout the major portion of the midpiece with the exception of the region occupied by the mitochondria. The flagellum contains a classic axoneme (9+2) and lacks lateral fins.

Details of sperm morphology

Figures

Fig. 6. Spermatozoa of Bryconamericus exodon. A-E: Longitudinal sections of spermatozoa. Note the lateral position of the nucleus (n) in relation to the flagellar axis and to proximal (p) and distal (d) centrioles, the position of the double nuclear fossa (double arrow), the mitochondria and the endomembrane system of the midpiece and the cytoplasmic canal (*) containing the initial segment of the flagellum (f). A-Inset: Detail of the position, shape and depth of the nuclear fossa, and the position of the centrioles to one another and to the nuclear fossa. F-L: Cross sections from the middle to the base of the nucleus and at different levels of the strongly asymmetric midpiece exposing the lateral position of the cytoplasmic canal (*) and of the flagellum (f), the distribution of the few elongate mitochondria (m) accumulated in larger portion of the midpiece and the lacy aspect of endomembrane system (v). L-Inset: Cross section of the flagellum with the classic axoneme (a).