Sperm Quality, Milt Biochemistry, and Cellular Ultrastructure in Fresh and Cryopreserved Sperm of Brycon amazonicus

Abstract

Milt cryopreservation facilitates native fish’s constant production of commercial interest. However, it can damage spermatozoa (sptz) due to the osmotic stress of diluents and low temperatures. This study compares spermatic quality in fresh (SF) and cryopreserved (CS) milt in B. amazonicus for 24 h, 1 month, and 3 months. Eight sexually mature males were induced with carp hypophysis extract. Milt was diluted in one proportion in a glucose solution (5.5%), egg yolk (12%), and dimethyl sulfoxide (10%). An evaluation of parameters such as motility, viability, morphology, total antioxidant capacity (TAC), and adenosine triphosphate (ATP) contents was performed at 24 h, 1 month, and 3 months, and the fertility test was conducted at 24 months of cryopreservation. The motility percentage was higher (p ≤ 0.05) in SF (95.5 ± 2.9%). Motility duration of SF was significantly higher (113.6 ± 22.6 s) than that of CS at 3 months (71 ± 12.2 s). The spermatic viability of SF was higher (97.1 ± 1%) in comparison with CS treatments. Sperm anomalies in SF were lower (12.4 ± 3.2%) than in all other treatments. ATP contents of (1.74 ± 4.5 nM × 10⁸ sptz) were superior only (p ≤ 0.05) in CS of 1 month (1.16 ± 1.2 nM × 10⁸ sptz). TAC was higher (p ≤ 0.05) in SF (26.46 ± 1.2 mM of Trolox [6-hydroxy-2,5,7,8-tetramethilcromane-acid 2-carboxylic]) compared to other CS treatments. However, there were not any significant differences in this parameter between cryopreservation times (p ≤ 0.05). Fertility rates were the same for all treatments. In terms of cellular ultrastructure, it was observed that B. amazonicus sptz had an oval-shaped head without an acrosome, middle part, and only one flagellum.