3D Atlas of the Pituitary Gland of the Model Fish Medaka (Oryzias latipes)

In vertebrates, the anterior pituitary plays a crucial role in regulating several essential physiological processes via the secretion of at least seven peptide hormones by different endocrine cell types. Comparative and comprehensive knowledge of the spatial distribution of those endocrine cell types is required to better understand their physiological functions. Using medaka as a model and several combinations of multi-color fluorescence in situ hybridization, we present the first 3D atlas revealing the gland-wide distribution of seven endocrine cell populations: lactotropes, thyrotropes, Lh and Fsh gonadotropes, somatotropes, and pomca-expressing cells (corticotropes and melanotropes) in the anterior pituitary of a teleost fish. By combining in situ hybridization and immunofluorescence techniques, we deciphered the location of corticotropes and melanotropes within the pomca-expressing cell population. The 3D localization approach reveals sexual dimorphism of tshba-, pomca-, and lhb-expressing cells in the adult medaka pituitary. Finally, we show the existence of bi-hormonal cells co-expressing lhb-fshb, fshb-tshba and lhb-sl using single-cell transcriptomics analysis and in situ hybridization. This study offers a solid basis for future comparative studies of the teleost pituitary and its functional plasticity.

Mercury Accumulation and Elimination in Different Tissues of Zebrafish (Danio rerio) Exposed to a Mercury-Supplemented Diet

In this study, we evaluated the bioaccumulation of mercury in zebrafish (Danio rerio) exposed to mercury-contaminated food for 21 days and the depuration of mercury for a subsequent post-exposure period of 28 days. Four tissues (muscle, liver, gills, and skin) were analyzed for mercury content. Overall, data indicated that Hg accumulation in the liver is faster than in other tissues. Furthermore, the liver is the tissue with the highest accumulation rate per day (0.021 µg Hg g−1 day−1), followed by muscle, skin, and gills. Conversely, the Hg depuration rates in different tissues showed the following order: gills > skin > muscle > liver. The bioaccumulation factor values of liver and muscle increased linearly during the uptake period. The ratios between mercury concentration in liver and muscle during the experiment also increased during the uptake period and remained higher than 1 during the elimination period, suggesting that Danio rerio needed more than 4 weeks of depuration. Finally, the distribution of Hg in the water column during the accumulation period is Hg particulate > Hg dissolved, and during the depuration period it is the opposite, mercury particulate < mercury dissolved. In conclusion, this study contributes to a better understanding of the differences in Hg dynamics during the accumulation and depuration stages in a model fish, also emphasizing the alterations on Hg available in the water column.

Image Driven Hydrological Components Based Fish Habitability Modeling in Riparian Wetlands Triggered by Damming

Assessing fish habitability in pursuance of damming for some selected fishes in wetland of Indo-Bangladesh barind tract using hydrological ingredients like hydro-period, water depth, and water presence consistency is major focus of the present study. Rule based decision tree modeling has been applied for integrating aforesaid hydrological parameters to find out habitat suitability for some selected fishes like carp fishes, shrimps, tilapia and cat fishes both for pre-dam and post-dam periods. From this work it is highlighted that damming has accelerated the rate of wetland deterioration in forms of hydrological flow alteration i.e. inconsistency in water presence has increased, hydro-duration became shortened and water depth has attenuated. From the model it is very clear that a small proportion area was considered to be good fish habitat (16.54–39.90%) in pre-dam period, but after damming almost all parts have become least suitable for fish habitability. Field survey has confirmed that fishing quantity, growing rate of fishes was higher in pre-dam situation but it is reduced gradually during post-dam period. Image driven hydrological parameters to model fish habitability is a new approach but important parameters like food availability, water quality parameters could also be incorporated in order to get better result.

Impacts of additional noise on the social interactions of a cooperatively breeding fish

Anthropogenic noise is a global pollutant known to affect the behaviour of individual animals in all taxa studied. However, there has been relatively little experimental testing of the effects of additional noise on social interactions between conspecifics, despite these forming a crucial aspect of daily life for most species. Here, we use established paradigms to investigate how white-noise playback affects both group defensive actions against an intruder and associated within-group behaviours in a model fish species, the cooperatively breeding cichlid Neolamprologus pulcher . Additional noise did not alter defensive behaviour, but did result in changes to within-group behaviour. Both dominant and subordinate females, but not the dominant male, exhibited less affiliation and showed a tendency to produce more submissive displays to groupmates when there was additional noise compared with control conditions. Thus, our experimental results indicate the potential for anthropogenic noise to affect social interactions between conspecifics and emphasize the possibility of intraspecific variation in the impacts of this global pollutant.

Thrombin-deficient mutant of medaka, a model fish, displays serious retardation in blood coagulation

ABSTRACT At the last stage of the blood coagulation cascade, thrombin plays a central role in the processing of fibrinogen for the polymerization and in the additional activation of Factor XIII for the stable cross-linking of fibrin. In addition, thrombin carries out possible multiple roles via processing or interaction with various functional proteins. Several studies conducted in order to elucidate additional physiological significance are ongoing. To clarify further significance of thrombin and to establish an associated disease model, we characterized the orthologue gene for medaka (Oryzias latipes), a research model fish. Tissue distribution of medaka prothrombin has been immunotechnically analyzed. Furthermore, thrombin-deficient medaka mutants were viably established by utilizing a genome-editing method. The established gene-deficient mutants exhibited retarded blood coagulation even in the heterozygous fish. Taking advantage of their ease of handling, this specific model is useful for further investigation in medical research areas on human coagulation diseases.

Putative Antimicrobial Peptides in Fish: Using Zebrafish as a Representative

Antimicrobial peptides (AMPs) are a group of short peptides in vertebrates, independently or derived from big proteins (AMP precursors), for innate immune adaptation to fight against exogenous pathogens. Therefore, they provide attractive templates for us to develop new alternatives to antibiotics, which will relieve the threats of microbial resistance and drug residual. Fish reside in various environments; however, AMP research in fish have long been lagged behind. These highly diverse peptides in fish, regardless whether they are digested from proteins or not, constitute a sophisticate line for host defense. Exploring AMPs’ detailed composition in fish will benefit us with a better understanding of them in vertebrates. This mini-review presents brief descriptions of AMPs and their research advances in fish, using zebrafish as the representative and comparing this model fish with well-studied amphibious mudskippers and tetraploid Atlantic salmon. Common features and species-specific characteristics among various fish provide valuable genetic resources for high-throughput development of novel antibiotic alternatives. In addition, the diversity and heterogeneity in tissue distribution also revealed the complex synergism of AMPs/AMP precursors. These big datasets of genomes and transcriptomes lay a solid foundation for theoretic researches and practical applications of AMPs in fish aquaculture and drug development.

The Proteins Interacting with Prmt5 in Medaka (Oryzias latipes) Identified by Yeast Two-Hybridization

Background: Prmt5 plays major role in regulation of gene expression, RNA processing, cell growth and differentiation, signal transduction, germ cell development, etc., in mammals. Prmt5 is also related to cancer. Knowing the proteins interacting with Prmt5 is important to understand Prmt5’s function in cells. Although there have been reports on proteins binding with Prmt5 in mammals, the partner proteins of Prmt5 in fish are still unclear. Objectives: The objective was to obtain proteins that bind with Prmt5 in medaka, a model fish. Methods: Yeast two hybridization was adopted to achieve the objective. Medaka Prmt5 was used as a bait to fish the prey, binding proteins in a cDNA library of medaka. Co-immunoprecipitation and in silicon analysis were performed to study the interaction of medaka Mep50 and Prmt5. Results: Eight proteins were identified to bind with Prmt5 from 69 preliminary positive colonies. The binding proteins are methylosome protein 50 (Mep50), apolipoprotein A-I-like (Apo-AI), PR domain containing protein 1a with zinc fingers (Prdm1a), Prdm1b, T-cell immunoglobulin mucin family member 3 (Tim-3), phosphoribosylaminoimidazole carboxylase and phosphoribosylaminoimidazolesuccinocarboxamide synthase (Paics), NADH dehydrogenase subunit 4 (ND4) and sciellin (Scl). Co-immunoprecipitation confirmed the interaction of medaka Prmt5 and Mep50. Predicted structures of medaka Prtm5 and Mep50 are similar to that of human PRMT5 and MEP50. Conclusion: Medaka Mep50, Prdm1a, Prdm1b, Apo-AI, Tim-3, Paics, ND4, and Scl bind with Prmt5.