Sperm cryopreservation of sex-reversed seven-band grouper, Epinephelus septemfasciatus

Cryopreservation of black seabream (Acanthopagrus schlegelii) sperm

In recent years, biotechnology has had a significant impact on the aquaculture industry, particularly in the field of breeding. Molecular selection breeding has emerged as a novel approach to breeding. Reducing the cost of genetic information for individuals with desirable traits after breeding has become an important research direction. Cryopreservation technology allows bypassing time and space constraints in genetic breeding, simplifying broodstock management. This study presents a detailed cryopreservation method for black seabream sperm, evaluating extender type, glucose concentration, cryoprotectant type and concentration, sperm-dilution ratio, and cooling protocols. Sperm motility parameters were analyzed using computer-assisted sperm analysis (CASA) before and after two days of freezing. This involved using an RS solution with a glucose concentration of 15 g/L and adding a 5% final concentration of EG as the sperm cryoprotectant. After mixing the sperm and solution at a ratio of 1:2, we subjected it to 5 min fumigation at 5 cm above the liquid nitrogen surface before plunging it into the nitrogen. Sperm motility reached 85.46 ± 7.32% after two days. Various enzymatic activities showed changes over 20 days post-cryopreservation. This improved cryopreservation protocol for black seabream sperm is beneficial for genetic breeding and reproduction and provides reference for studying the cryodamage mechanisms of black seabream sperm.

Complete mitochondrial genome of the hybrid grouper Hyporthodus septemfasciatus (♀)×Epinephelus moara (♂) (Perciformes, Serranidae) and results of a phylogenetic analysis

The complete mitochondrial genome of the hybrid grouper Hyporthodus septemfasciatus (♀)×Epinephelus moara (♂) was obtained by next-generation sequencing. The mitochondrial genome was 16,499 bp long, consisting of 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and a control region (D-loop). The overall base composition is 28.62% A, 28.27% C, 16.27% G, and 26.84% T with 55.46% A + T. In the maximum-likelihood (ML) phylogenetic analysis, the hybrid grouper belonged to the same clade as H. septemfasciatus (maternal inheritance).

Changes in sperm parameters of sex-reversed female mandarin fish Siniperca chuatsi during cryopreservation process

This works studies the physiological characteristics (sperm motility characteristics) and biochemical characteristics (DNA damage, enzymes activities and fertilization ability) of fresh and freeze-thawed semen of sex-reversed female mandarin fish Siniperca chuatsi (n = 30) obtained with the application of 17α-methyl testosterone for sex reversal. The fresh sperm motility and fertilization rate of sex-reversed females were about 83% and 70% respectively which had no significant difference with normal males (p > 0.05). Except for the value of DNA damage, other values of sperm motility, related enzymes activities and fertilization rate of sex-reversed female sperm declined after a process of cryopreservation (p < 0.05). But the frozen sperm can still get nearly 60% of the fertilization rate. This study identified the physiological and biochemical characteristics of the fresh and cryopreserved sperm from sex-reversed female mandarin fish, and the sex-reversed female spermatozoa can be used for actual production.

Effects of different diluents, cryoprotective agents, and freezing rates on sperm cryopreservation in Epinephelus akaara

We investigated various factors, including cryoprotective agents (CPAs), diluents, and freezing rates, to develop an optimal cryopreservation protocol for Epinephelus akaara sperm. In experiments using 10% dimethyl sulfoxide (DMSO), glycerol, and methanol with various diluents, 10% DMSO and 300 mM glucose yielded the highest post-thaw sperm motility. The combination of 10% glycerol and 300 mM sucrose yielded significantly higher post-thaw sperm motility than did combinations using other diluents. Glycerol and DMSO at a concentration of 10% as CPAs with 300 mM glucose as the diluent resulted in the highest MSR and sperm activity index (SAI). An investigation to determine the effects of glycerol and DMSO concentrations on post-thaw sperm survival rate revealed no significant differences among 5, 10, 15, and 20% concentrations of either CPA. In assessing the effects of CPA concentration on the fertilization rate, the 10% concentration yielded the highest fertilization rate (81.4 ± 4.3%) in DMSO, whereas 15% was the optimal concentration for glycerol (fertilization rate = 66.7 ± 6.1%). The hatching rate was also highest in 10% DMSO (40.1 ± 0.4%) and in 15% glycerol (27.8 ± 2.3%). In conclusion, the optimal rates of post-thaw sperm motility, fertilization, and hatching were achieved when E. akaara sperm were cryopreserved in a diluent of 300 mM glucose with 10% DMSO as the CPA at a freezing rate of -5 °C/min. We therefore recommend this protocol for the cryopreservation of E. akaara sperm.