Semen characterization and sperm structure of the Amazon tambaqui Colossoma macropomum

Abstract

Seminal features of tambaqui were evaluated after hormonal induction of spermiation with common carp pituitary extract. Seventeen adult (6.1 ± 0.9 kg, 62 ± 6 cm) males were collected from earthen ponds and transported to indoor concrete tanks. Semen was evaluated according to volume, pH, osmolality, motility, concentration, viability, sperm morphometry and morphological abnormalities. The semen of tambaqui was white and milky. The volume was 10.2 ± 5.1 mL at pH 8.0 ± 0.1, and yielded a concentration of 9.1 × 109 spermatozoa mL−1 while seminal plasma osmolality was 260 ± 7.3 mOsm kg−1. The percentage of viable sperm cells was determined with 97.0 ± 2.0% and 87.0 ± 8.0% using an eosin-nigrosin staining and fluorescent live-dead kit (propidium iodide and SYBR-14), respectively. A negative correlation (−0.65) between semen pH and sperm motility was observed suggesting this feature might influence the tambaqui sperm kinetics. Morphometrically the spermatozoa were on average 35.48 ± 1.55 μm long with a roundish head (mean length: 2.73 ± 0.21 μm; mean width: 2.58 ± 0.18 μm; n = 250 spermatozoa), without an acrosome, and presented a long midpiece (2.90 ± 0.52 μm) and flagellum (29.84 ± 1.63 μm). About 15.8% of the spermatozoa carried morphological abnormalities, with bent tail being the most frequent defect (7.81 ± 3.12%). The characterization of tambaqui semen favors the development of more precise and efficient procedures for its analysis and utilization in controlled breeding.