Reduced Life Expectancy Model Analyses of Exposure Time Effects of Endocrine Disruptors to Teleost Fishes Based on Effect Concentration of Hepatic Biomarkers

In this current paper, the exposure time effects on four endocrine disruptors and teleost fishes were evaluated using the reduced life expectancy (RLE) model based on the effect concentration (EC50) of available literature published. The result on the regression analysis over different exposure times has demonstrated that the EC50 of hepatic biomarkers falls with increasing exposure times in a predictable manner. The slopes of the regression equations reflect the strength of the toxic effects on the various teleost fish. The EC50 reduction over time can be interpreted based on the bioconcentration process, which can be used to understand transfer routes of the compounds from water to fish body. RLE model also provides useful information in assessing the toxic effects on fish life expectancy as a result of the occurrence of compounds.

Effect of Fertilizer Diammonium Phosphate on Liver,Kidney and Muscle 5-Nucleotidase Activity of Fresh Water Teleost Fish Clarias batrachus

The toxic effect of fertilizer Diammonium phosphate resulted in alterations of 5'-Nucleotidase activity of tissues liver, kidney and muscles offish C. batrachus at varying intervals and exposures. Alterations in 5'-Nuclcotidase activity of body organs gave an idea of the toxicity caused by the fertilizer. Thus the enzyme 5'-Nucleotidase can be used to monitor the pollution in aquatic ecosystem.

Antimicrobial roles of phagocytosis in teleost fish:Phagocytic B cells vs professional phagocytes

The defense system of teleost fish organized on innate and adaptive immunity protects them against a wide variety of pathogenic microorganisms in the aquatic environment.Phagocytosis is one of the most effective defense strategies against microbial challenge mainly performed by classical‘professional’phagocytes(including monocytes,macrophages and granulocytes).They contain,kill and process the internalized pathogens for antigen presentation by providing antigenic ligands to initiate activation and clonal expansion of T and B cells,which bridge the innate and adaptive immunity.The discovery of phagocytic B cells in teleost fish has broken the paradigm that primary vertebrate B cells are lack of phagocytosis of particulates,as well as led to the investigation of phagocytic activity of mammalian B-1 B cells.The active phagocytic,microbicidal capabilities and antigen presentation in teleost phagocytic B cell have demonstrated to be similar as professional phagocytes,providing a potential impact on development of new vaccination strategies to prevent and control infectious diseases.In this review,we aim to address current progress on the antimicrobial role of phagocytic B cells in teleost fish by comparing it with other professional phagocytes and mammalian B-1 B cells,and provide the application prospect of phagocytic B cells in developing vaccines as well as the prevention of fish diseases.

Role of brain-derived neurotrophic factor during the regenerative response after traumatic brain injury in adult zebrafish

Several mammalian animal models of traumatic brain injury have been used, mostly rodents. However, reparative mechanisms in mammalian brain are very limited, and newly formed neurons do not survive for long time. The brain of adult zebrafish, a teleost fish widely used as vertebrate model, possesses high regenerative properties after injury due to the presence of numerous stem cells niches. The ventricular lining of the zebrafish dorsal telencephalon is the most studied neuronal stem cell niche because its dorso-lateral zone is considered the equivalent to the hippocampus of mammals which contains one of the two constitutive neurogenic niches of mammals. To mimic TBI, stab wound in the dorso-lateral telencephalon of zebrafish was used in studies devoted to fish regenerative properties. Brain-derived neurotrophic factor, which is known to play key roles in the repair process after traumatic brain lesions, persists around the lesioned area of injured telencephalon of adult zebrafish. These results are extensively compared to reparative processes in rodent brain. Considering the complete repair of the damaged area in fish, it could be tempting to consider brain-derived neurotrophic factor as a factor contributing to create a permissive environment that enables the establishment of new neuronal population in damaged brain.

Unexpected complex horizontal gene transfer in teleost fish

Horizontal gene transfer(HGT)is a common occurrence across all domains of life.However,most HGT events were reported between single-celled organisms or parasites and hosts(Van Etten and Bhattacharya 2020).A type II antifreeze protein(AFP)gene was the first and sole evidence of HGT direct vertebrate-to-vertebrate DNA transmission.AFP is only found in 3 widely separated branches of teleost fishes(herring,sea raven,and smelts),sharing amino acid similarity up to 80%(Graham et al.2008).

Identification and functional characterization of fish IL‑17 receptors suggest important roles in the response to nodavirus infection

Th17 is a lymphocyte T helper(Th)subpopulation relevant in the control and regulation of the immune response characterized by the production of interleukin(IL)-17.This crucial cytokine family acts through their binding to the IL-17 receptors(IL-17R),having up to six members.Although the biology of fish Th17 is well-recognized,the molecular and functional characterization of IL-17 and IL-17R has been limited.Thus,our aim was to identify and characterize the IL-17R repertory and regulation in the two main Mediterranean cultured fish species,the gilthead seabream(Sparus aurata)and the European sea bass(Dicentrarchus labrax).Our in silico results showed the clear identification of six members in each fish species,from IL-17RA to IL-17RE-like,with well-conserved gene structure and protein domains with their human orthologues.All of them showed wide and constitutive transcription in naïve tissues but with highest levels in mucosal tissues,namely skin,gill or intestine.In leucocytes,T mitogens showed the strongest up-regulation in most of the il17 receptors though il17ra resulted in inhibition by most stimulants.Interestingly,in vivo nodavirus infection resulted in alterations on the transcription of il17 receptors.While nodavirus infection led to some increments in the il17ra,il17rb,il17rc and il17rd transcripts in the susceptible European sea bass,many down-regulations were observed in the resistant gilthead seabream.Our data identify the presence and conservation of six coding IL-17R in gilthead seabream and European sea bass as well as their differential regulation in vitro and upon nodavirus infection.

Long noncoding RNA AANCR modulates innate antiviral responses by blocking miR-210-dependent MITA downregulation in teleost fish,Miichthys miiuy

Viral infection induces the initiation of antiviral effectors and cytokines which are critical mediators of innate antiviral responses.The critical molecular determinants are responsible for triggering an appropriate immune response.Long noncoding RNAs(lncRNAs)have emerged as new gene modulators involved in various biological processes,while how lncRNAs operate in lower vertebrates are still unknown.Here,we discover a long noncoding RNA,termed antiviral-associated long noncoding RNA(AANCR),as a novel regulator for innate antiviral responses in teleost fish.The results indicate that fish MITA plays an essential role in host antiviral responses and inhibition of Siniperca chuatsi rhabdovirus(SCRV)production.miR-210 reduces MITA expression and suppress MITA-mediated antiviral responses,which may help viruses evade host antiviral responses.Further,AANCR functions as a competing endogenous RNA(ceRNA)for miR-210 to control protein abundance of MITA,thereby inhibiting SCRV replication and promoting antiviral responses.Our data not only shed new light on understanding the function role of lncRNA in biological processes in teleost fish,but confirmed the hypothesis that ceRNA networks exist widely in vertebrates.

Do human activities influence survival and orientation abilities of larval fishes in the ocean?

The larval stages of most marine fishes spend days to weeks in the pelagic environment,where they must find food and avoid predators in order to survive.Some fish only spend part of their life history in the pelagic environment before returning to their adult habitat,for example,a coral reef.The sensory systems of larval fish develop rapidly during the first few days of their lives,and here we concentrate on the various sensory cues the fish have available to them for survival in the pelagic environment.We focus on the larvae of reef fishes because most is known about them.We also review the major threats caused by human activities that have been identified to have worldwide impact and evaluate how these threats may impact larval-fish survival and orientation abilities.Many human activities negatively affect larval-fish sensory systems or the cues the fish need to detect.Ultimately,this could lead to decreased numbers of larvae surviving to settlement,and,therefore,to decreased abundance of adult fishes.Although we focus on species wherein the larvae and adults occupy different habitats(pelagic and demersal,respectively),it is important to acknowledge that the potential anthropogenic effects we identify may also apply to larvae of species like tuna and herring,where both larvae and adults are pelagic.

Lateral line system of fish

The lateral line is a sensory system that allows fishes to detect weak water motions and pressure gradients.The smallest functional unit of the lateral line is the neuromast,a sensory structure that consists of a hair cell epithelium and a cupula that connects the ciliary bundles of the hair cells with the water surrounding the fish.The lateral line of most fishes consists of hundreds of superficial neuromasts spread over the head,trunk and tail fin.In addition,many fish have neuromasts embedded in lateral line canals that open to the environment through a series of pores.The present paper reviews some more recent aspects of the morphology,behavioral relevance and physiology of the fish lateral line.In addition,it reports some new findings with regard to the coding of bulk water flow.

DNA microarray technology and its application in fish biology and aquaculture

Fishery is an important industry in China as well as in the rest of the world,and it provides a human food resource containing high-quality protein.Best practice in aquaculture requires a full understanding of the genomic controls and transcriptional profiles of cultured fish species.Improvements in aquaculture can be made by regulation of the expression of functional genes.Microarray technology is a powerful tool for rapid screening of genes or transcriptional profiles in a particular fish or for a particular economic character;for example,genes that are related to growth and disease control in the fish.This review provides a brief introduction to microarray technology and its methods and applications,together with a discussion of the achievements in fish biology that have resulted from this technology.

Neuropeptide Y and melanocortin receptors in fish:regulators of energy homeostasis

Energy homeostasis,which refers to the physiological processes that the energy intake is exquisitely coordinated with energy expenditure,is critical for survival.Therefore,multiple and complex mechanisms have been involved in the regulation of energy homeostasis.The central melanocortin system plays an important role in modulating energy homeostasis.This system includes the orexigenic neurons,expressing neuropeptide Y/Agouti-related protein(NPY/AgRP),and the anorexigenic neurons expressing proopiomelanocortin(POMC).The downstream receptors of NPY,AgRP and post-translational products of POMC are G protein-coupled receptors(GPCRs).This review summarizes the compelling evidence demonstrating that NPY and melanocortin receptors are involved in energy homeostasis.Subsequently,the comparative studies on physiology and pharmacology of NPY and melanocortin receptors in humans,rodents and teleosts are summarized.Also,we provide a strategy demonstrating the potential application of the new ligands and/or specific variants of melanocortin system in aquaculture.

Radiographic and tomographic description of marlin sucker Remora osteochir, Pisces: Echeneidae—preliminary data of one specimen

Remoras are commensal fish of various marine species,such as sharks,swordfishes,turtles,dolphins,manta rays and whales.One specimen of marlin sucker Remora osteochir was evaluated using computed tomography for skeletal digital reconstruction,digital radiology for general evaluation and bone counting,and the double contrast technique to distinguish coelomic organs.In radiographic images,it was possible to observe otoliths in the center of the neurocranium,to count 27 vertebrae,nine pairs of ribs,and to detect the presence of the hipural and epural bones near of the caudal fin.In double contrast images,it was possible to visualize the swim bladder,gills,heart,liver,stomach and intestines.From the tomographic images and reconstructions,it was possible to identify the intercalar bones of the cephalic disc;the spine with vertebral bodies composed of neural arches and ventral ribs;and the pectoral girdle formed by posttemporal,cleithrum and scapulocoracoid bones.It was concluded that digital radiology and computed tomography were able to describe anatomical structures of marlin sucker R.osteochir without the need for dissection.