Effect of different oxidative stress degrees generated by hydrogen peroxide on motility and DNA fragmentation of zebrafish (Danio rerio) spermatozoa

A multiplier peroxiporin signal transduction pathway powers piscine spermatozoa

The primary task of a spermatozoon is to deliver its nuclear payload to the egg to form the next-generation zygote. With polyandry repeatedly evolving in the animal kingdom, however, sperm competition has become widespread, with the highest known intensities occurring in fish. Yet, the molecular controls regulating spermatozoon swimming performance in these organisms are largely unknown. Here, we show that the kinematic properties of postactivated piscine spermatozoa are regulated through a conserved trafficking mechanism whereby a peroxiporin ortholog of mammalian aquaporin-8 (Aqp8bb) is inserted into the inner mitochondrial membrane to facilitate H₂O₂ efflux in order to maintain ATP production. In teleosts from more ancestral lineages, such as the zebrafish (Danio rerio) and the Atlantic salmon (Salmo salar), in which spermatozoa are activated in freshwater, an intracellular Ca²⁺-signaling directly regulates this mechanism through monophosphorylation of the Aqp8bb N terminus. In contrast, in more recently evolved marine teleosts, such the gilthead seabream (Sparus aurata), in which spermatozoa activation occurs in seawater, a cross-talk between Ca²⁺- and oxidative stress-activated pathways generate a multiplier regulation of channel trafficking via dual N-terminal phosphorylation. These findings reveal that teleost spermatozoa evolved increasingly sophisticated detoxification pathways to maintain swimming performance under a high osmotic stress, and provide insight into molecular traits that are advantageous for postcopulatory sexual selection.

Oxidative Stress and DNA Damage of Zebrafish Sperm at Different Stages of the Cryopreservation Process

Although gamete cryopreservation has facilitated advancement of reproduction research by allowing the storage of cells over prolonged periods of time, during freezing-thawing cycles, cells inevitably suffer from cryoinjuries. Here, we evaluate oxidative stress and DNA damage of zebrafish sperm at different stages of the cryopreservation process. It was generally observed that the freezing and thawing of the samples led to an increase in the generation of reactive oxygen species and the activity of the catalase enzyme and a reduction in the generation of sulfhydryl groups and superoxide dismutase activity. The alkaline comet assay demonstrated that DNA damage increased after equilibration time, with an even greater increase after freezing and thawing. The comet assay modified with the enzyme formamidopyrimidine glycosylase, and Endonuclease III demonstrated greater DNA damage than the standard comet assay, demonstrating a high degree of oxidation of purines and pyrimidines at all stages of cryopreservation. Our results show that the freeze and thaw processes cause greater oxidative stress and DNA damage than cryoprotectant toxicity during exposure at the equilibrium stage.

Sperm Quality Assessment in Honey Bee Drones

The quality of honey bee drone semen is relevant in different contexts, ranging from colony productivity to pathology, toxicology and biodiversity preservation. Despite its importance, considerably less knowledge is available on this subject for the honey bee when compared to other domestic animal species. A proper assessment of sperm quality requires a multiple testing approach which discriminates between the different aspects of sperm integrity and functionality. Most studies on drone semen quality have only assessed a few parameters, such as sperm volume, sperm concentration and/or sperm plasma membrane integrity. Although more recent studies have focused on a broader variety of aspects of semen quality, some techniques currently used in vertebrates, such as computer-assisted sperm analysis (CASA) or multiparametric sperm quality testing, still remain to be developed in the honey bee. This may be attributed to the particular sperm morphology and physiology in this species, requiring the development of technologies specifically adapted to it. This article reviews the present knowledge of sperm quality in honey bee drones, highlighting its peculiarities and proposing future lines of research.

Diet Supplemented with Antioxidant and Anti-Inflammatory Probiotics Improves Sperm Quality after Only One Spermatogenic Cycle in Zebrafish Model

Infertility is a medical concern worldwide and could also have economic consequences in farmed animals. Developing an efficient diet supplement with immediate effects on sperm quality is a promising tool for human reproduction and for domesticated animal species. This study aims at elucidating the effect of a short-time probiotic supplementation consisting of a mixture of two probiotic bacteria with proven antioxidant and anti-inflammatory activities on zebrafish sperm quality and male behavior. For this purpose, three homogeneous groups of males in terms of motility (<60%) were established. The control group was fed with a normal standard diet. The other received supplements: One group (vehicle control) was fed with maltodextrin and the other received a probiotic preparation based on a mixture (1:1) of Lactobacillus rhamnosus CECT8361 and Bifidobacterium longum CECT7347. The feeding regime was 21 days corresponding with a single spermatogenesis in zebrafish. The preparation did not modify animal weight, positively affected the number of fluent males, increased sperm concentration, total motility, progressive motility, and fast spermatozoa subpopulations. Moreover, the animals fed with the supplement showed different behavior patterns compared to control groups. Our results suggest a diet-related modulation on the exploration activity indicating a lower stress-like conduct. The studied formulation described here should be considered as advantageous in male reproductive biotechnology.