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.

Background: Chronic stress can produce a severe negative impact on health not only in the exposed individuals but also in their offspring. Indeed, chronic stress may be contributing to the current worldwide scenario of increasing infertility and decreasing gamete quality in human populations. Here, we evaluate the effect of chronic stress on behavior and male reproductive parameters in zebrafish. Our goal is to provide information on the impact that chronic stress has at molecular, histological, and physiological level in a vertebrate model species. Results: We evaluated the effects of a 21-day chronic stress protocol covering around three full waves of spermatogenesis in Danio rerio adult males. The induction of chronic stress produced anxiety-like behavior in stressed males as assessed by a novel tank test. At a molecular level, the induction of chronic stress consistently resulted in the overexpression of two genes related to endoplasmic reticulum (ER) stress in the brain. Gene set enrichment analysis (GSEA) of testes suggested a dysregulation of the nonsense-mediated decay (NMD) pathway, which was also confirmed on qPCR analysis. Histological analysis of the testicle did not show significant differences in terms of the relative proportions of each germ-cell type; however, the quality of sperm from stressed males was compromised in terms of motility. RNA-seq analysis in stress-derived larval progenies revealed molecular alterations, including those predicted to affect translation initiation, DNA repair, cell cycle control, and response to stress. Conclusions: Induction of chronic stress during a few cycles of spermatogenesis in the vertebrate zebrafish model affects behavior, gonadal gene expression, final gamete quality, and progeny. The NMD surveillance pathway (a key cellular mechanism that regulates the stability of both normal and mutant transcripts) is severely affected in the testes by chronic stress and therefore the control and regulation of RNAs during spermatogenesis may be affected altering the molecular status in the progeny. Graphical

With increasing evidence showing the connections between the microbiome, neurophysiology, and behavior, our research endeavors to investigate whether the consumption of a combination of two postbiotics with antioxidant effects can affect behavior regulation in model species. Here, we worked with a combination (1:1 ratio) of heat-treated Bifidobacterium longum subsp. longum ES1 (CECT7347) and Lacticaseibacillus rhamnosus BPL15 (CECT8361) as a dietary supplement. To examine the potential benefit of using this formulation to alleviate anxiety-like behavior, we employed two model species, Caenorhabditis elegans and adult Danio rerio. In C. elegans, the postbiotic supplementation reduced the anxiety-related behavior analyzed by means of the octanol avoidance test. In zebrafish, the novel tank test indicated a different swimming pattern 2 and 4 months after the animals were fed with the postbiotic combination. While fish did not exhibit any variance in their locomotion parameters such as pace and speed, they showed a statistically significant preference to spend more time in the upper zone of the water tank, a behavior that is correlated with a lower anxiety-like behavior in these species. Our aim with this study is to present evidence that can be used to develop whole-cell postbiotic-based novel and innovative dietary supplements for anxiety-related conditions.

Manipulation is usually required for biomass calculation and food estimation for optimal fish growth in production facilities. However, the advances in computer-based systems have opened a new range of applied possibilities. In this study we used image analysis and a neural network algorithm that allowed us to successfully provide highly accurate biomass data. This developed system allowed us to compare the effects of reduced levels of human-animal interaction on the culture of adult Senegalese sole (Solea senegalensis) in terms of body weight gain. For this purpose, 30 adult fish were split into two homogeneous groups formed by three replicates (n = 5) each: a control group (CTRL), which was standard manipulated and an experimental group (EXP), which was maintained under a lower human-animal interaction culture using our system for biomass calculation. Visible implant elastomer was, for the first time, applied as tagging technology for tracking soles during the experiment (four months). The experimental group achieved a statistically significant weight gain (p < 0.0100) while CTRL animals did not report a statistical before-after weight increase. Individual body weight increment was lower (p < 0.0100) in standard-handled animals. In conclusion, our experimental approach provides evidence that our developed system for biomass calculation, which implies lower human-animal interaction, improves biomass gain in Senegalese sole individuals in a short period of time.