CD10+ Cells and IgM in Pathogen Response in Lumpfish (Cyclopterus lumpus) Eye Tissues

Glyphosate and its formulated product Roundup Transorb R® affect locomotor activity and reproductive and developmental parameters in Jenynsia lineata fish: An intergenerational study

Glyphosate is the most widely utilized herbicide worldwide due to its effectiveness in controlling agricultural weeds. However, its persistence in aquatic ecosystems has raised concerns about the well-being of non-target organisms such as fish. This study aimed to evaluate the effects of chronic exposure (21 days) to glyphosate or its formulated product Roundup Transorb R®, at an environmentally relevant concentration permitted by regulations in certain countries (65 μg/L of glyphosate), on the locomotor activity and reproductive success of the fish Jenynsia lineata, as well as on the morphology/development and locomotor activity of its offspring, as intergenerational effects. Neither the pure nor formulated herbicide altered the distance traveled and velocity of adult fish exposed to the herbicide (F0), but they negatively affected reproductive success, decreasing the percentage of positive response to the presence of the female, reducing the number of gravid females, causing abortions, and lowering offspring survival (F1). In the F1 generation, a decrease in weight and length was noted along with developmental abnormalities in both treatment groups (pure or formulated glyphosate), with the formulation causing more harm. Observed developmental abnormalities included muscle atrophy, ascites, pigmentary disorders, vertebral agenesis, spinal deviation, and exophthalmia. Furthermore, parental exposure to pure glyphosate led to an increase in the distance traveled and velocity of F1 (hyperlocomotion), whereas exposure to the formulated product resulted in a decrease in these behaviors (hypolocomotion) of F1. These findings highlight the toxic effects of glyphosate at very low concentrations, although varying between pure and formulated, and demonstrate the intergenerational consequences of herbicide exposure, underscoring the risk to the survival of fish offspring in glyphosate-contaminated environments.

Systematic analysis of ocular features and responses of cultured spotted wolffish (Anarhichas minor)

A better understanding of unique anatomical and functional features of the visual systems of teleost fish could provide key knowledge on how these systems influence the health and survival of these animals in both wild and culture environments. We took a systematic approach to assess some of the visual systems of spotted wolffish (Anarhichas minor), a species of increasing importance in North Atlantic aquaculture initiatives. The lumpfish (Cyclopterus lumpus) was included in these studies in a comparative manner to provide reference. Histology, light and electron microscopy were used to study the spatial distribution and occurrence of cone photoreceptor cells and the nature of the retinal tissues, while immunohistochemistry was used to explore the expression patterns of two photoreceptor markers, XAP-1 and XAP-2, in both species. A marine bacterial infection paradigm in lumpfish was used to assess how host-pathogen responses might impact the expression of these photoreceptor markers in these animals. We define a basic photoreceptor mosaic and present an ultrastructural to macroscopic geographical configuration of the retinal pigment tissues in both animals. Photoreceptor markers XAP-1 and XAP-2 have novel distribution patterns in spotted wolffish and lumpfish retinas, and exogenous pathogenic influences can affect the normal expression pattern of XAP-1 in lumpfish. Live tank-side ophthalmoscopy and spectral domain optical coherence tomography (SD-OCT) revealed that normal cultured spotted wolffish display novel variations in the shape of the retinal tissue. These two complementary imaging findings suggest that spotted wolffish harbour unique ocular features not yet described in marine teleosts and that visual function might involve specific retinal tissue shape dynamics in these animals. Finally, extensive endogenous biofluorescence is present in the retinal tissues of both animals, which raises questions about how these animals might use retinal tissue in novel ways for visual perception and/or communication. This work advances fundamental knowledge on the visual systems of two economically important but now threatened North Atlantic teleosts and provides a basic foundation for further research on the visual systems of these animals in health versus disease settings. This work could also be useful for understanding and optimizing the health and welfare of lumpfish and spotted wolffish in aquaculture towards a one health or integrative perspective.

Transcriptome profiling of lumpfish (Cyclopterus lumpus) head kidney to Renibacterium salmoninarum at early and chronic infection stages

Renibacterium salmoninarum causes Bacterial Kidney Disease (BKD) in several fish species. Atlantic lumpfish, a cleaner fish, is susceptible to R. salmoninarum. To profile the transcriptome response of lumpfish to R. salmoninarum at early and chronic infection stages, fish were intraperitoneally injected with either a high dose of R. salmoninarum (1 × 109 cells dose-1) or PBS (control). Head kidney tissue samples were collected at 28- and 98-days post-infection (dpi) for RNA sequencing. Transcriptomic profiling identified 1971 and 139 differentially expressed genes (DEGs) in infected compared with control samples at 28 and 98 dpi, respectively. At 28 dpi, R. salmoninarum-induced genes (n = 434) mainly involved in innate and adaptive immune response-related pathways, whereas R. salmoninarum-suppressed genes (n = 1537) were largely connected to amino acid metabolism and cellular processes. Cell-mediated immunity-related genes showed dysregulation at 98 dpi. Several immune-signalling pathways were dysregulated in response to R. salmoninarum, including apoptosis, alternative complement, JAK-STAT signalling, and MHC-I dependent pathways. In summary, R. salmoninarum causes immune suppression at early infection, whereas lumpfish induce a cell-mediated immune response at chronic infection. This study provides a complete depiction of diverse immune mechanisms dysregulated by R. salmoninarum in lumpfish and opens new avenues to develop immune prophylactic tools to prevent BKD.

Climate change can impair bacterial pathogen defences in sablefish via hypoxia-mediated effects on adaptive immunity

Low-oxygen levels (hypoxia) in aquatic habitats are becoming more common because of global warming and eutrophication. However, the effects on the health/disease status of fishes, the world's largest group of vertebrates, are unclear. Therefore, we assessed how long-term hypoxia affected the immune function of sablefish, an ecologically and economically important North Pacific species, including the response to a formalin-killed Aeromonas salmonicida bacterin. Sablefish were held at normoxia or hypoxia (100% or 40% air saturated seawater, respectively) for 6-16 weeks, while we measured a diverse array of immunological traits. Given that the sablefish is a non-model organism, this involved the development of a species-specific methodological toolbox comprised of qPCR primers for 16 key immune genes, assays for blood antibacterial defences, the assessment of blood immunoglobulin (IgM) levels with ELISA, and flow cytometry and confocal microscopy techniques. We show that innate immune parameters were typically elevated in response to the bacterial antigens, but were not substantially affected by hypoxia. In contrast, hypoxia completely prevented the ∼1.5-fold increase in blood IgM level that was observed under normoxic conditions following bacterin exposure, implying a serious impairment of adaptive immunity. Since the sablefish is naturally hypoxia tolerant, our results demonstrate that climate change-related deoxygenation may be a serious threat to the immune competency of fishes.

Increased water temperature contributes to a chondrogenesis response in the eyes of spotted wolffish

Adult vertebrate cartilage is usually quiescent. Some vertebrates possess ocular scleral skeletons composed of cartilage or bone. The morphological characteristics of the spotted wolffish (Anarhichas minor) scleral skeleton have not been described. Here we assessed the scleral skeletons of cultured spotted wolffish, a globally threatened marine species. The healthy spotted wolffish we assessed had scleral skeletons with a low percentage of cells staining for the chondrogenesis marker sex-determining region Y-box (Sox) 9, but harboured a population of intraocular cells that co-express immunoglobulin M (IgM) and Sox9. Scleral skeletons of spotted wolffish with grossly observable eye abnormalities displayed a high degree of perochondrial activation as evidenced by cellular morphology and expression of proliferating cell nuclear antigen (PCNA) and phosphotyrosine. Cells staining for cluster of differentiation (CD) 45 and IgM accumulated around sites of active chondrogenesis, which contained cells that strongly expressed Sox9. The level of scleral chondrogenesis and the numbers of scleral cartilage PCNA positive cells increased with the temperature of the water in which spotted wolffish were cultured. Our results provide new knowledge of differing Sox9 spatial tissue expression patterns during chondrogenesis in normal control and ocular insult paradigms. Our work also provides evidence that spotted wolffish possess an inherent scleral chondrogenesis response that may be sensitive to temperature. This work also advances the fundamental knowledge of teleost ocular skeletal systems.

CD45 in ocular tissues during larval and juvenile stages and early stages of V. anguillarum infection in young lumpfish (Cyclopterus lumpus)

Immune responses to infectious diseases impacting lumpfish (Cyclopterus lumpus) eye tissue are only starting to be studied at a molecular and histopathological level. In this study, we extend our understanding of lumpfish sensory organ anatomy, of components of the lumpfish nasal and ocular immune system and the nature of the intraocular response to Vibrio anguillarum infection. We have evaluated the expression of cluster of differentiation (CD) 45 protein, a tyrosine phosphatase, in larval and juvenile lumpfish tissues in order to spatially survey ocular and related head structures that may participate in early stages of intraocular immune responses. We provide here a histological mapping of the larval lumpfish nasal chamber system since its connectively with the eye though mucosal epithelia have not been explored. These results build upon our growing understanding of the lumpfish intraocular immune response to pathogens, exemplified herein by experimental nasally delivered V. anguillarum infection. CD45 is developmentally regulated in lumpfish eyes and periocular anatomy with early expression appearing in larvae in corneal epithelium and in nasal structures adjacent to the eye. Normal juvenile and adult lumpfish eyes express CD45 in the corneal epithelium, in leukocyte cells within blood vessel lumens of the rete mirabile, choroid body and choriocapillaris vasculatures. Experimental nasally delivered V. anguillarum infection led to qualitative and quantitative changes in CD45 expression in head kidney renal tubule tissues by 7 days post infection (dpi). The same animals showed redistribution and upregulation of corneal epithelial CD45 expression, corneal epithelial dysplasia and an increased frequency of CD45⁺ cells in ocular vasculature. Interestingly, while CD45 upregulation and/or CD45⁺ cell infiltration into inner ocular and retinal tissues was not observed under this experimental scenario, subtle neural retinal changes were observed in infected fish. This work provides new fundamental knowledge on North Atlantic teleost visual systems and vision biology in general.

Immune response of silver pomfret (Pampus argenteus) to Amyloodinium ocellatum infection

Amyloodinium ocellatum (AO) infection in silver pomfret (Pampus argenteus) causes extensive mortality. Insufficient information exists on the molecular immune response of silver pomfret to AO infestation, so herein we simulated the process of silver pomfret being infected by AO. Translucent trophosomes were observed on the gills of AO-infected fish. Transcriptome profiling was performed to investigate the effects of AO infection on the gill, kidney complex and spleen. Overall, 404,412,298 clean reads were obtained, assembling into 96,341 unigenes, which were annotated against public databases. In total, 2730 differentially expressed genes were detected, and few energy- and immune-related genes were further assessed using RT-qPCR. Moreover, activities of three immune-related (SOD, AKP and ACP) and three energy-related (PKM, LDH and GCK) enzymes were determined. AO infection activated the immune system and increased interleukin-1 beta and immunoglobulin M heavy chain levels. Besides, the PPAR signalling pathway was highly enriched, which played a role in improving immunity and maintaining homeostasis. AO infection also caused dyspnoea, leading to extensive lactic acid accumulation, potentially contributing towards a strong immune response in the host. Our data improved our understanding regarding the immune response mechanisms through which fish coped with parasitic infections and may help prevent high fish mortality in aquaculture.