Brachyhypopomus, Mago-Leccia, 1994, Mago-Leccia, 1994

Giora, Júlia & Burns, John R., 2011, Sperm ultrastructure in three different families of weakly electric fishes (Teleostei: Gymnotiformes), Neotropical Ichthyology 9 (4), pp. 881-888 : 882

Results

Spermatozoa of Brachyhypopomus draco , Brachyhypopomus bombilla and Brachyhypopomus gauderio - Hypopomidae .

The spermatozoa of the three analyzed species are characterized by a well defined head, midpiece, and single flagellum. Both the head and nucleus tend to be spherical in B. draco (head, Fig. 1F ; nucleus Fig. 1 G-H-I), but ovoid in B. gauderio (head, Fig. 1A ; nucleus, Fig. 1 B-C) and B. bombilla (head, Fig. 1K ; nucleus, Fig. 1 M-N). Nuclear diameter is 1.0 µm for B. draco ; length and width nuclear measurements are 1.7 x 2.8 µm for B. gauderio and 0.9 x 1.8 µm for B. bombilla . Nuclear chromatin is condensed and granular in all three species, with extensive areas of lighter chromatin seen only in B. bombilla ( Fig. 1 M-N).All species undergo nuclear rotation. The proximal centriole is anterior, slightly lateral and perpendicular to the distal. Electron-dense material is associated with both centrioles. The proximal centriole and most of the distal are contained within a deep nuclear fossa ( Fig. 1 C-I-M). Only in B. gauderio does the fossa branch extensively throughout the nucleus ( Fig. 1B ). The midpiece contains several elongate mitochondria and a large number of vesicles, some of which contain stainable material ( Fig. 1 B-D-G-H-M).An open cytoplasmic canal is only observed immediately posterior to the centriolar complex in B. gauderio ( Fig. 1C ) and B. draco ( Fig. 1I ) but this may close more posteriorly.An open cytoplasmic canal is not apparent in B. bombilla . An area of more organized membranous structures is only observed in the midpiece of B. draco ( Fig. 1 G-J). The flagellum has the classic 9 + 2 microtubular pattern and does not show intratubular differentiation, both tubules of each peripheral doublet being electron-lucent ( Fig 1 E-J-L). The flagellar membrane does not have lateral projections or fins in any of the species. However, there is substantially more cytoplasm between the axoneme and flagellar membrane in B. bombilla ( Fig. 1L ).

Figures

Fig. 1. (next page) A-F-K: Spermatozoa of Brachyhypopomus gauderio, Brachyhypopomus draco, and Brachyhypopomus bombilla respectively (SEM), h = sperm head, arrow = flagellum, double arrow = midpiece; B-C: Spermatozoa of B. gauderio in longitudinal section (TEM) showing ovoid nucleus (n), deep nuclear fossa (nf), centriolar arrangement (dc= distal centriole, pc=proximal centriole),open cytoplasmatic canal(cc), and presence of vesicles (v) containing some electron-dense material, f = flagellum; D: Midpiece of spermatozoa of B. gauderio in cross section (TEM) showing cytoplasmatic canal (cc)and elongate mitochondrion (m); E:Flagella ofspermatozoa of B. gauderio in cross section (TEM) showing electron-lucent tubules ofeach peripheral doublet (arrow);G-H-I: Spermatozoa of B. draco in longitudinal section (TEM) showing spherical nucleus (n), centriolar arrangement (dc= distal centriole, pc= proximal centriole), open cytoplasmatic canal (cc), elongate mitochondria (m), and presence of vesicles (v) containing some electron-dense materialand forming an organized membranous structure; J:Midpiece and flagellum of spermatozoaof B.draco in cross section (TEM) showing vesicles (v) forming an organized membranous structure, and electron-lucent tubules of each peripheral doublet (arrow); L: Flagella of spermatozoa of B. bombilla in longitudinal and cross section (TEM) showing electron-lucent tubules of each peripheral doublet (arrow), and cytoplasm located between axoneme (a) and flagellar membrane(asterisk); M-N: Spermatozoaof B.bombilla in longitudinal section (TEM) showing ovoid nucleus with extensive areas of lighter chromatin (n), centriolar arrangement (dc= distal centriole, pc= proximal centriole), elongate mitochondria (m), and presence of vesicles (v) containing some electron-dense material.Scale bars = 1µm.