Seasonal and age-related changes in semen characteristics and composition of seminal plasma in sex-reverse female rainbow trout (Oncorhynchus mykiss) in comparison with normal males

Effects of captan, mancozeb and azoxystrobin fungicides on motility, oxidative stress and fatty acid profiles in rainbow trout (Oncorhynchus mykiss) spermatozoa

An in vitro study using rainbow trout spermatozoa was designed to evaluate the toxic effects of different concentrations of captan (CPT), mancozeb (MCZ), and azoxystrobin (AZX) fungicides on motility parameters, lipid peroxidation, SOD activity, total antioxidant capacity (TAC), and DPPH inhibition. Moreover, changes in fatty acids profiles caused by the fungicides were determined for the first time. The results revealed that motility parameters, SOD activities, TAC values, and DPPH inhibitions decreased significantly while lipid peroxidation increased after ≥2 µg/L of CPT, ≥1 µg/L of MCZ, and ≥5 µg/L of AZX incubations for 2 h at 4 °C. Additionally, 10 µg/L CPT, 5 µg/L MCZ, and 200 µg/L AZX reduced motility to the 50 % level. Our results clearly demonstrated significant changes in the fatty acids profiles of spermatozoa exposed to these concentrations of the fungicides. The highest lipid peroxidation and the lowest monounsaturated and polyunsaturated saturated fatty acids (MUFA and PUFA, respectively) were detected in AZX. Even though the susceptibility of spermatozoa to oxidative damage is generally attributed to PUFA contents, the results of this study have represented that MUFA content could play a part in this tendency. Moreover, the lower concentration of MCZ reduced motility to the % 50 level while it deteriorated the fatty acids profile less than did AZX. Overall, the present study demonstrated that the detrimental effects of the fungicides on mitochondrial respiration and related enzymes have more priority than oxidative stress in terms of their toxicities on spermatozoa. It has also been suggested that fish spermatozoa are a good model for determining changes in the fatty acid profiles by fungicides, probably, by other pesticides and environmental contaminants as well.

UPLC-QTOF/MS Metabolomics and Biochemical Assays Reveal Changes in Hepatic Nutrition and Energy Metabolism during Sexual Maturation in Female Rainbow Trout (Oncorhynchus mykiss)

Mobilization and repartition of nutrients and energy are prerequisites for the normal sexual maturity of broodstock. However, there are few studies on the mechanisms of hepatic nutrients and energy metabolism during sexual maturation in female rainbow trout (Oncorhynchus mykiss). This study investigated hepatic metabolite changes and explored the potential nutritional regulation mechanism between mature and immature female rainbow trout by combining UPLC-QTOF/MS metabolomics and biochemical assays. It was observed that hepatic biochemical assays differed considerably between the two groups, such as glucose, triglycerides, hexokinase, lipase, and aspartate aminotransferase. Liver metabolomics showed that various differential metabolites involved in amino acid and lipid metabolism markedly increased, suggesting the enhancement of lipid metabolism and amino acid anabolism in the liver provides the necessary material basis for ovarian development. Meanwhile, glycogen catabolism and glycolysis hold the key to maintaining organismal energy homeostasis with normal sexual maturation of female rainbow trout. Overall, the results from this study suggested that the liver undergoes drastic reprogramming of the metabolic profile in response to mobilization and repartition of nutrients and energy during the sexual maturation of female rainbow trout. This study further deepened the understanding of the reproductive biology of rainbow trout, and provided the theoretical basis and practical ramifications for nutritional requirements of breeding high-quality broodstock in the artificial propagation of rainbow trout.

Genome-Wide Association Study Identifies Genomic Loci of Sex Determination and Gonadosomatic Index Traits in Large Yellow Croaker (Larimichthys crocea)

Larimichthys crocea is one of the traditional marine culture fishes in China, widely distributed in South China Sea, East Sea, and southern Yellow Sea. Sex dimorphism is evident in this species that females present a substantial growth strength than males, suggesting breeding females could obtain more economic benefits in L. crocea aquaculture industry. With the continuous expansion of aquaculture industry, both identifying sex-associated genome region and understanding the genetic basis underlying gonad differentiation and development matter to not only sex control aquaculture but also breeding industry. Thus, genome-wide association analysis (GWAS) of sex determination was conducted with a random breeding population of 905 individuals (including 463 females and 442 males) by ddRAD sequencing. For sex determination, 21 significant single nucleotide polymorphisms (SNPs) in chromosome (Chr) 22 were identified. Surrounding these SNPs, we founded 14 candidate genes, including dmrt1, dmrt3, and piwil2, fam102a, and odf2. The sex-associated region was narrowed down further to 2.4 Mb on Chr22 through F_st scanning and insertion-deletion (InDel) analysis. Besides, 3 SNPs in the supposed sex-determining region on Chr22 were identified as highly associated with gonad differentiation through GWAS on gonadosomatic index (GSI) in 350 males and 231 females. Because of the significant difference of GSI between females and males of L. crocea, GWAS on GSI of different genders was also conducted independently. Finally, we identified a SNP in Chr18 showing genome-wide significant association with male GSI (MGSI) and three genes axl, cyp2a10, and cyp2g1 involved in the gonadal development regulation process of aromatase. Overall, this study explored the genetic basis of sex determination mechanism and provided novel insights into gonad differentiation and development, offering solid genetic support for sex control breeding, marker-assisted selection, and marine resources conservation.

Characteristics and Cryopreservation of Semen of Sex-Reversed Females of Salmonid Fish

Sex reversal has been used as a breeding strategy by salmonid fish to produce genetically and phenotypically single sex populations. Production of all-female fish has great importance for the creation of monosex female triploids of salmonid fish, which are valued for their sterility, lack of female maturation, and larger commercial size. Among salmonids, the majority of rainbow trout (Oncorhynchus mykiss) production is based on all-female production with a high proportion of all-female triploid production in Europe. The main aim of this review is to present the recent knowledge regarding sex-reversed females (SRFs) of salmonid fish. We discuss the methods of sex reversal as well as their effects on the morphology and histology of the reproductive tract. We focus on the characteristics of SRF semen as well as the factors determining semen quality. The lower quality of SRF sperm compared to that of normal males has resulted in the need for the artificial maturation of semen. Most importantly, methods of semen storage-both short-term and long-term (cryopreservation)-that can improve hatchery operations are presented with the special emphasis on recent progress in development of efficient cryopreservation procedures and use of cryopreserved semen in hatchery practice. Moreover, we also address the emerging knowledge concerning the proteomic investigations of salmonid sperm, focusing primarily on the proteomic comparison of normal male and SRF testicular semen and presenting changes in SRF rainbow trout sperm proteome after in vitro incubation in artificial seminal plasma.

Protein profile of Dabry's sturgeon (Acipenser dabryanus) spermatozoa and relationship to sperm quality

Knowledge of conditions affecting sperm quality is essential for efficient culture of fish for commercial purposes and conservation of species. Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry were used to characterize the proteomic profile of Acipenser dabryanus spermatozoa relative to motility and fertilization capacity. There were differential amounts of protein in 313 spots in spermatozoa of males classified to have relatively greater or lesser spermatozoa quality. The functions of 43 of 50 selected proteins were identified. The proteins in 14 spots were involved in metabolism, and of these, proteins in 11 spots were highly abundant in spermatozoa of males categorized to have spermatozoa of greater quality, including pyruvate kinase, enolase B, phosphoglycerate kinase, lactate dehydrogenase, cytosolic malate dehydrogenase, brain creatine kinase b, Ckmb protein, and nucleoside diphosphate kinase. The proteins involved in mechanics of flagellum movement were identified, including the dynein intermediate chain, radial spoke head 1 homolog; ropporin-1-like, Bardet-Biedl syndrome 5, ADP-ribosylation factor-like protein 3, tektin-4, gamma-actin, and tubulin cytoskeleton proteins to be differentially abundant in spermatozoa that were classified relatively greater or lesser quality. Heat shock proteins, copper/zinc superoxide dismutase and peroxiredoxins, which are involved in stress response were of differential abundance in spermatozoa from males with spermatozoa in the two different classification groups. Proteins were also detected that are involved in protein folding and binding, or hydrolase activity. The results are valuable for the prediction of sperm quality and for reproduction management in A. dabryanus and other threatened species.