Discovery of an unconventional lamprey lymphocyte lineage highlights divergent features in vertebrate adaptive immune system evolution.

Lymphocyte receptors independently evolved in both jawed and jawless vertebrates with similar adaptive immune responses. However, the diversity of functional subtypes and molecular architecture in jawless vertebrate lymphocytes, comparable to jawed species, is not well defined. Here, we profile the gills, intestines, and blood of the lamprey, Lampetra morii, with single-cell RNA sequencing, using a full-length transcriptome as a reference. Our findings reveal higher tissue-specific heterogeneity among T-like cells in contrast to B-like cells. Notably, we identify a unique T-like cell subtype expressing a homolog of the nonlymphoid hematopoietic growth factor receptor, MPL-like (MPL-L). These MPL-L+ T-like cells exhibit features distinct from T cells of jawed vertebrates, particularly in their elevated expression of hematopoietic genes. We further discovered that MPL-L+ VLRA+ T-like cells are widely present in the typhlosole, gill, liver, kidney, and skin of lamprey and they proliferate in response to both a T cell mitogen and recombinant human thrombopoietin. These findings provide new insights into the adaptive immune response in jawless vertebrates, shedding new light on the evolution of adaptive immunity.

In vitro fish mucosal surfaces producing mucin as a model for studying host-pathogen interactions.

Current prophylactic and disease control measures in aquaculture highlight the need of alternative strategies to prevent disease and reduce antibiotic use. Mucus covered mucosal surfaces are the first barriers pathogens encounter. Mucus, which is mainly composed of highly glycosylated mucins, has the potential to contribute to disease prevention if we can strengthen this barrier. Therefore, aim of this study was to develop and characterize fish in vitro mucosal surface models based on commercially available cell lines that are functionally relevant for studies on mucin regulation and host-pathogen interactions. The rainbow trout (Oncorhynchus mykiss) gill epithelial cell line RTgill-W1 and the embryonic cell line from Chinook salmon (Oncorhynchus tshawytscha) CHSE-214 were grown on polycarbonate membrane inserts and chemically treated to differentiate the cells into mucus producing cells. RTGill-W1 and CHSE-214 formed an adherent layer at two weeks post-confluence, which further responded to treatment with the γ-secretase inhibitor DAPT and prolonged culture by increasing the mucin production. Mucins were metabolically labelled with N-azidoacetylgalactosamine 6 h post addition to the in vitro membranes. The level of incorporated label was relatively similar between membranes based on RTgill-W1, while larger interindividual variation was observed among the CHSE in vitro membranes. Furthermore, O-glycomics of RTgill-W1 cell lysates identified three sialylated O-glycans, namely Galß1-3(NeuAcα2-6)GalNAcol, NeuAcα-Galß1-3GalNAcol and NeuAcα-Galß1-3(NeuAcα2-6)GalNAcol, resembling the glycosylation present in rainbow trout gill mucin. These glycans were also present in CHSE-214. Additionally, we demonstrated binding of the fish pathogen A. salmonicida to RTgill-W1 and CHSE-214 cell lysates. Thus, these models have similarities to in vivo mucosal surfaces and can be used to investigate the effect of pathogens and modulatory components on mucin production.

Identification of the effects of alkalinity exposure on the gills of oriental river prawns, Macrobrachium nipponense.

Macrobrachium nipponense is an important commercial freshwater species in China. However, the ability of alkali tolerance of M. nipponense is insufficient to culture in the major saline-alkali water source in China. Thus, it is urgently needed to perform the genetic improvement of alkali tolerance in this species. In the present study, we aimed to analyse the effects of alkali treatment on gills in this species after 96 h alkalinity exposure under the alkali concentrations of 0 mmol/L, 4 mmol/L, 8 mmol/L, and 12 mmol/L through performing the histological observations, measurement of antioxidant enzymes, metabolic profiling analysis, and transcriptome profiling analysis. The results of the present study revealed that alkali treatment stimulated the contents of malondialdehyde, glutathione, glutathione peroxidase in gills, indicating these antioxidant enzymes plays essential roles in the protection of body from the damage, caused by the alkali treatment. In addition, high concentration of alkali treatment (> 8 mmol/L) resulted in the damage of gill membrane and haemolymph vessel, affecting the normal respiratory function of gill. Metabolic profiling analysis revealed that Metabolic pathways, Biosynthesis of secondary metabolites, Biosynthesis of plant secondary metabolites, Microbial metabolism in diverse environments, Biosynthesis of amino acids were identified as the main enriched metabolic pathways of differentially expressed metabolites, which are consistent with the previous publications, treated by the various environmental factors. Transcriptome profiling analyses revealed that the alkali concentration of 12 mmol/L has more regulatory effects on the changes of gene expression than the other alkali concentrations. KEGG analysis revealed that Phagosome, Lysosome, Glycolysis/Gluconeogenesis, Purine Metabolism, Amino sugar and nucleotide sugar metabolism, and Endocytosis were identified as the main enriched metabolic pathways in the present study, predicting these metabolic pathways may be involved in the adaption of alkali treatment in M. nipponense. Phagosome, Lysosome, Purine Metabolism, and Endocytosis are immune-related metabolic pathways, while Glycolysis/Gluconeogenesis, and Amino sugar and nucleotide sugar metabolism are energy metabolism-related metabolic pathways. Quantitative PCR analyses of differentially expressed genes (DEGs) verified the accuracy of the RNA-Seq. Alkali treatment significantly stimulated the expressions of DEGs from the metabolic pathways of Phagosome and Lysosome, suggesting Phagosome and Lysosome play essential roles in the regulation of alkali tolerance in this species, as well as the genes from these metabolic pathways. The present study identified the effects of alkali treatment on gills, providing valuable evidences for the genetic improvement of alkali tolerance in M. nipponense.

Four new species of Cichlidogyrus (Platyhelminthes, Monopisthocotyla, Dactylogyridae) from Lake Victoria haplochromine cichlid fishes, with the redescription of C. bifurcatus and C. longipenis.

African cichlids are model systems for evolutionary studies and host-parasite interactions, because of their adaptive radiations and because they harbour many species of monogenean parasites with high host-specificity. Five locations were sampled in southern Lake Victoria: gill-infecting monogeneans were surveyed from 18 cichlid species belonging to this radiation superflock and two others representing two older and distantly related lineages. We found one species of Gyrodactylidae, Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011, and seven species of Dactylogyridae. Four are described herein: Cichlidogyrus pseudodossoui n. sp., Cichlidogyrus nyanza n. sp., Cichlidogyrus furu n. sp., and Cichlidogyrus vetusmolendarius n. sp. Another Cichlidogyrus species is reported but not formally described (low number of specimens, morphological similarity with C. furu n. sp.). Two other species are redescribed: C. bifurcatus Paperna, 1960 and C. longipenis Paperna & Thurston, 1969. Our results confirm that the monogenean fauna of Victorian littoral cichlids displays lower species richness and lower host-specificity than that of Lake Tanganyika littoral cichlids. In C. furu n. sp., hooks V are clearly longer than the others, highlighting the need to re-evaluate the current classification system that considers hook pairs III-VII as rather uniform. Some morphological features of C. bifurcatus, C. longipenis, and C. nyanza n. sp. suggest that these are closely related to congeners that infect other haplochromines. Morphological traits indicate that representatives of Cichlidogyrus colonised Lake Victoria haplochromines or their ancestors at least twice, which is in line with the Lake Victoria superflock being colonised by two cichlid tribes (Haplochromini and Oreochromini).

Title: Quatre espèces nouvelles de Cichlidogyrus (Plathelminthes, Monopisthocotyla, Dactylogyridae) parasites d'haplochrominés (Cichlidae) du lac Victoria, avec la redescription de C. bifurcatus et C. longipenis. Abstract: Les cichlidés africains sont des systèmes modèles pour les études évolutives et les interactions hôtes-parasites, en raison de leurs radiations adaptatives et parce qu'ils hébergent de nombreuses espèces de monogènes parasites avec une spécificité d'hôte étroite. Cinq sites ont été échantillonnés dans le sud du lac Victoria, les monogènes infectant les branchies ont été étudiés chez 18 espèces de cichlidés appartenant à ce superflock et de deux autres espèces représentant deux lignées plus anciennes et éloignées. Nous avons trouvé une espèce de Gyrodactylidae, Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011, et sept espèces de Dactylogyridae. Quatre sont décrites ici : Cichlidogyrus pseudodossoui n. sp., Cichlidogyrus nyanza n. sp., Cichlidogyrus furu n. sp. et Cichlidogyrus vetusmolendarius n. sp. Une autre espèce de Cichlidogyrus est signalée mais non formellement décrite (faible nombre de spécimens, similarité morphologique avec C. furu n. sp.). Deux autres espèces sont redécrites : C. bifurcatus Paperna, 1960 et C. longipenis Paperna & Thurston, 1969. Nos résultats confirment que la faune des monogènes des cichlidés du littoral du lac Victoria présente une richesse en espèces et une spécificité d'hôte inférieures à celles des cichlidés du littoral du lac Tanganyika. Chez C. furu n. sp., les crochets V sont clairement plus longs que les autres, ce qui souligne la nécessité de réévaluer le système de classification actuel qui considère que les crochets III-VII sont plutôt uniformes. Certaines caractéristiques morphologiques de C. bifurcatus, C. longipenis et C. nyanza n. sp. suggèrent que ceux-ci sont étroitement liés aux congénères qui infectent les autres haplochrominés. Les traits morphologiques indiquent que les représentants de Cichlidogyrus ont colonisé les haplochrominés du lac Victoria ou leurs ancêtres au moins deux fois, ce qui concorde avec le fait que le superflock du lac Victoria a été colonisé par deux tribus de cichlidés (Haplochromini et Oreochromini).

Deciphering deep-sea chemosynthetic symbiosis by single-nucleus RNA-sequencing.

Bathymodioline mussels dominate deep-sea methane seep and hydrothermal vent habitats and obtain nutrients and energy primarily through chemosynthetic endosymbiotic bacteria in the bacteriocytes of their gill. However, the molecular mechanisms that orchestrate mussel host-symbiont interactions remain unclear. Here, we constructed a comprehensive cell atlas of the gill in the mussel Gigantidas platifrons from the South China Sea methane seeps (1100 m depth) using single-nucleus RNA-sequencing (snRNA-seq) and whole-mount in situ hybridisation. We identified 13 types of cells, including three previously unknown ones, and uncovered unknown tissue heterogeneity. Every cell type has a designated function in supporting the gill's structure and function, creating an optimal environment for chemosynthesis, and effectively acquiring nutrients from the endosymbiotic bacteria. Analysis of snRNA-seq of in situ transplanted mussels clearly showed the shifts in cell state in response to environmental oscillations. Our findings provide insight into the principles of host-symbiont interaction and the bivalves' environmental adaption mechanisms.

NEW INSIGHTS BASED ON MORPHOLOGICAL AND MOLECULAR DATA REVEAL THE TAXONOMIC STATUS OF HALIOTREMA PTEROISI (MONOGENOIDEA: DACTYLOGYRIDAE) INFECTING DEVIL FIREFISH PTEROIS MILES (PERCIFORMES: SCORPAENOIDEI: SCORPAENIDAE) IN THE RED SEA OFF EGYPT.

HALIOTREMA PTEROISI: Paperna, 1972 (Monogenoidea: Dactylogyridae) was found parasitizing the gill lamellae of devil firefish, Pterois miles (Bennet) (Perciformes: Scorpaenidae), in the Red Sea off Safaga (26°44'N, 33°56'E), Egypt. The parasite species was described based on morphological features of available specimens and transferred to PlatycephalotremaKritsky and Nitta, 2019 (Dactylogyridae) as Platycephalotrema pteroisi (Paperna, 1972) n. comb. The occurrence of Pl. pteroisi off Safaga, Egypt, represented a range extension for the helminth of about 160 km to the southwest of the southern end of the Gulf of Aqaba. The transfer of the species to Platycephalotrema based on an evaluation of morphological features was supported by an analysis of molecular sequences of the 28S rDNA gene of Pl. pteroisi and 49 other dactylogyrid species. Maximum-likelihood, Bayesian inference, and maximum parsimony analyses of this dactylogyrid sequence data revealed H. pteroisi to nest with significant support within the clade of Platycephalotrema spp. During the literature review of dactylogyrid species infecting scorpionfishes, it was determined that Ancyrocephalus sp. of Dyer et al. from luna lion fish Pterois lunulata Temminck and Schlegel collected off Okinawa-jima, Japan represented an undescribed species of Platycephalotrema.

Novel insights on microbiome dynamics during a gill disease outbreak in farmed rainbow trout (Oncorhynchus mykiss).

The generic term "Gill disease" refers to a wide range of disorders that affect the gills and severely impact salmonid aquaculture systems worldwide. In rainbow trout freshwater aquaculture, various etiological agents causing gill diseases have been described, particularly Flavobacterium and Amoeba species, but research studies suggest a more complex and multifactorial aetiology. Here, a cohort of rainbow trout affected by gill disease is monitored both through standard laboratory techniques and 16S rRNA Next-Generation Sequencing (NGS) analysis during a natural disease outbreak and subsequent antibiotic treatment with Oxytetracycline. NGS results show a clear clustering of the samples between pre- and post-treatment based on the microbial community of the gills. Interestingly, the three main pathogenic bacteria species in rainbow trout (Yersinia ruckeri, Flavobacterium psychrophilum, and Flavobacterium branchiophilum) appear to be weak descriptors of the diversity between pre-treatment and post-treatment groups. In this study, the dynamics of the gill microbiome during the outbreak and subsequent treatment are far more complex than previously reported in the literature, and environmental factors seem of the utmost importance in determining gill disease. These findings present a potential novel perspective on the diagnosis and management of gill diseases, showing the limitations of conventional laboratory methodologies in elucidating the complexity of this disease in rainbow trout. To the authors' knowledge, this work is the first to describe the microbiome of rainbow trout gills during a natural outbreak and subsequent antibiotic treatment. The results of this study suggest that NGS can play a critical role in the analysis and comprehension of gill pathology. Using NGS in future research is highly recommended to gain deeper insights into such diseases correlating gill's microbiome with other possible cofactors and establish strong prevention guidelines.

Characteristics and pathogenicity of Vibrio alginolyticus SWS causing high mortality in mud crab (Scylla serrata) aquaculture in Hong Kong.

Introduction: Vibrio alginolyticus is a Gram-negative, rod-shaped bacterium belonging to the family of Vibrionaceae, a common pathogen in aquaculture animals, However, studies on its impact on Scylla serrata (mud crabs) are limited. In this study, we isolated V. alginolyticus SWS from dead mud crab during a disease outbreak in a Hong Kong aquaculture farm, which caused up to 70% mortality during summer. Methods: Experimental infection and histopathology were used to investigate the pathogenicity of V. alginolyticus SWS in S. serrata and validate Koch's postulates. Comprehensive whole-genome analysis and phylogenetic analysis antimicrobial susceptibility testing, and biochemical characterization were also performed. Results: Our findings showed that V. alginolyticus SWS caused high mortality (75%) in S. serrata with infected individuals exhibiting inactivity, loss of appetite, decolored and darkened hepatopancreas, gills, and opaque muscle in the claw. Histopathological analysis revealed tissue damage and degeneration in the hepatopancreas, gills, and claw muscle suggesting direct and indirect impacts of V. alginolyticus SWS infection. Conclusions: This study provides a comprehensive characterization of V. alginolyticus SWS as an emerging pathogen in S. serrata aquaculture. Our findings underscore the importance of ongoing surveillance, early detection, and the development of targeted disease management strategies to mitigate the economic impact of vibriosis outbreaks in mud crab aquaculture.

Genetics and ontogeny are key factors influencing thermal resilience in a culturally and economically important bivalve.

Increasing seawater temperatures coupled with more intense and frequent heatwaves pose an increasing threat to marine species. In this study, the New Zealand green-lipped mussel, Perna canaliculus, was used to investigate the effect of genetics and ontogeny on thermal resilience. The culturally and economically significant mussel P. canaliculus (Gmelin, 1971) has been selectively-bred in New Zealand for two decades, making it a unique biological resource to investigate genetic interactions in a temperate bivalve species. Six selectively-bred full sibling families and four different ages, from early juveniles (6, 8, 10 weeks post-fertilisation) to sub-adults (52 weeks post-fertilisation), were used for experimentation. At each age, each family was exposed to a three-hour heat challenge, followed by recovery, and survival assessments. The shell lengths of live and dead juvenile mussels were also measured. Gill tissue samples from sub-adults were collected after the thermal challenge to quantify the 70 kDa heat shock protein gene (hsp70). Results showed that genetics, ontogeny and size influence thermal resilience in P. canaliculus, with LT50 values ranging between 31.3 and 34.4 °C for all studied families and ages. Juveniles showed greater thermotolerance compared to sub-adults, while the largest individuals within each family/age class tended to be more heat sensitive than their siblings. Sub-adults differentially upregulated hsp70 in a pattern that correlated with net family survival following heat challenge, reinforcing the perceived role of inducible HSP70 protein in molluscs. This study provides insights into the complex interactions of age and genotype in determining heat tolerance of a key mussel species. As marine temperatures increase, equally complex selection pressure responses may therefore occur. Future research should focus on transcriptomic and genomic approaches for key species such as P. canaliculus to further understand and predict the effect of genetic variation and ontogeny on their survival in the context of climate change.

Effects of ammonia nitrogen stress on the physiological, biochemical, and metabolic levels of the gill tissue of juvenile four-finger threadfin (Eleutheronema tetradactylum).

In this study, the impact of ammonia nitrogen stress on juvenile four-finger threadfin in pond culture was examined. The 96-hour median lethal concentration (LC50-96h) and safe concentration of ammonia nitrogen were assessed in juveniles with a body weight of 7.4 ± 0.6 g using ecotoxicological methods. The study design included a stress group exposed to LC50-96h levels of ammonia nitrogen and a control group without ammonia nitrogen exposure. To examine the physiological, biochemical, and metabolic effects of ammonia nitrogen on gill tissue, gill tissue samples were collected after 12, 24, 48, and 96 h of stress, with a resumption of treatment after 48 h. Compared to the control group, ammonia nitrogen adversely affected juvenile four-finger threadfin, with LC50-96h and safe concentration values of 20.70 mg/L and 2.07 mg/L, respectively. Exposure to ammonia nitrogen resulted in substantial gill damage, including fusion of lamellae, epithelial cell loss, and proliferation of chlorine-secreting cells. This tissue damage persisted even after a 48-h recovery period. Ammonia nitrogen stress triggered an increase in antioxidant enzyme activity (superoxide dismutase, catalase, and glutathione peroxidase) and malondialdehyde levels in gills, indicating oxidative stress from 12 h onwards. Although enzyme activity decreased over time, oxidative stress persisted even after recovery, suggesting an ongoing need for antioxidant defense. Metabolomics analysis showed significant alterations in 423 metabolites under ammonia nitrogen stress. Key metabolites such as L-arginine, taurine, 20-hydroxyarachidonic acid, 11,12-dihydroxy-5Z, 8Z, and 14Z eicosotrienic acid followed an increasing trend; uridine, adenosine, L-glutathione, and thymidine 5'-triphosphate followed a decreasing trend. These changes reflect metabolic adaptations to stress. In enriched metabolic pathways, the main differential pathways are membrane transport, lipid metabolism, and amino acid metabolism. After 48 h, significant differences were observed in 396 metabolites compared to the control group. Notably, L-arginine, choline, and L-histidine increased, while linoleic acid, adenosine, and glutathione decreased. Amino acid and lipid metabolism pathways were key affected pathways. Under ammonia nitrogen stress, juvenile four-finger threadfin increased the synthesis of unsaturated and saturated fatty acids to cope with low temperatures and bolster immune function by consuming spermidine. This adaptation helps to clear peroxides generated during fatty acid synthesis, thereby protecting cells from oxidative damage. This study provides insights for pond aquaculture and breeding of ammonia nitrogen-tolerant fish strains.

Toxicological effects of Honokiol on zebrafish and its underlying mechanism.

The compound Honokiol, derived from the bark of Magnolia officinalis, possesses the ability to induce apoptosis and inhibit cellular damage caused by reactive oxygen species. The objective of this study was to investigate the toxicological and histopathological effects of Honokiol on zebrafish (Danio rerio) through conducting a semistatic acute toxicity test involving immersion in an Honokiol-containing solution. The results showed that the toxic effects of Honokiol on zebrafish were primarily manifested in the liver and gills. When exposed to 0.6 mg/L of Honokiol, it could lead to liver hemorrhage as well as swelling and necrosis of gill tissues, and high concentrations of Honokiol could trigger inflammatory responses. Additionally, research found that Honokiol could induce apoptosis in liver and gill tissues through the P53 pathway and possessed the ability to enhance antioxidation. The present findings significantly contribute to a more profound understanding of the toxic impact of Honokiol and its underlying mechanism, thereby providing a valuable reference for the future safe utilization of Honokiol and related pharmaceutical advancements.

Construction of a Full-Length transcriptome resource for the African sharptooth catfish (Clarias gariepinus), a prototypical air-breathing Fish, based on isoform sequencing (Iso-Seq).

The African sharptooth catfish (Clarias gariepinus) assumes significance in aquaculture, given its role as a farmed freshwater species with modified gill structures functioning as an air-breathing organ (ABO). To provide a scientific basis for further elucidating the air-breathing formation mechanism and deeply utilizing the genetic resources of Clarias gariepinus, we utilized the PacBio sequencing platform to acquire a comprehensive full-length transcriptome from five juvenile developmental stages and various adult tissues, including the ABO, gills, liver, skin, and muscle. We generated 25,766,688 high-quality reads, with an average length of 2,006 bp and an N50 of 2,241 bp. Following rigorous quality control, 34,890 (97.7 %) of the high-quality isoforms were mapped to the reference genome for gene and transcript annotation, yielding 387 novel isoforms and 14,614 new isoforms. Additionally, we identified 28,582 open reading frames, 48 SNPs, 5,464 variable splices, and 6,141 variable polyadenylation sites, along with 475 long non-coding RNAs. Many DEGs were involved with low oxygen GO terms and KEGG pathways, such as response to stimulus, biological regulation and catalytic activities. Furthermore, it was found that transcription factors such as zf-C2H2, Homeobox, bHLH, and MYB could underpin the African sharptooth catfish's developmental plasticity and its capacity to adapt its morphology and function to its environment. Through the comprehensive analysis of its genomic characteristics, it was found that the African sharptooth catfish has developed a series of unique respiratory adaptive mechanisms during the evolutionary process, These results not only advances the understanding of genetic adaptations to hypoxia in Clarias fish but also provides a valuable framework for future studies aimed at improving aquaculture practices,besides provide important references and inspirations for the evolution of aquatic organisms.

Gill lesions are the main cause of death in yellowfin seabream (Acanthopagrus latus) following infection with Amyloodinium ocellatum.

Amyloodiniosis, caused by the ectoparasite Amyloodinium ocellatum, affects the healthy development of mariculture. This study used a local infection method to identify the pathogenic target organ responsible for the death of infected fish. Comparing the relationship between the abundance of trophonts in gills and skin with the mortality of infected fish using local infection showed that severe gill infections cause the mortality of infected fish. At the 40 % survival rate of infected fish, the parasite abundance in the gill was 14,167 ± 4371. The gill filaments of the infected fish were structurally disordered, with pronounced lesions associated with the presence of trophonts, such as epithelial cell degeneration and massive lymphocytic infiltration. However, the skin showed no obvious pathological changes. The TUNEL assay showed a significant presence of apoptotic cells concentrated in the area of A. ocellatum infection. The trophonts on the gills developed faster than those parasitising the skin and fins. Microbiome analysis revealed that at the phylum level, Proteobacteria, Bacteroidota, and Firmicutes are abundant in the skin, while Verrucomicrobiota, Bacteroidota, and Proteobacteria are abundant in the gills of A. latus. Furthermore, A. ocellatum infection significantly reduced (p < 0.05) the richness and diversity of the gill microbial community of A. latus. Infection by A. ocellatum increased the relative abundance of several putative pathogenic bacteria (Flavobacterium and Nocardia) in the gill and skin of A. latus, possibly increasing the likelihood of disease in the host. In conclusion, these results evidenced that severe gill infections by A. ocellatum cause mortality in infected fish, which clarifies the direction for exploring the pathogenesis of amyloodiniosis.

A NOVEL SPECIES OF MYXOBOLUS (CNIDARIA: MYXOSPOREA: MYXOBOLIDAE) FROM THE GILL OF GREEN SUNFISH, LEPOMIS CYANELLUS (PERCIFORMES: CENTRARCHIDAE), FROM THE BLACK RIVER OF NORTHEASTERN ARKANSAS.

During March 2023, 7 green sunfish (Lepomis cyanellus) and 2 bluegill (Lepomis macrochirus) were collected from the Black River (White River drainage) in Lawrence County, Arkansas. In addition, during March 2023 and again in May-June 2023, 13 L. cyanellus and 6 L. macrochirus were taken from Butcherknife and Big Fork creeks (Ouachita River drainage), Polk County, Arkansas, 9 L. cyanellus were collected from the Caddo River, Montgomery County, Arkansas, and 5 green sunfish were taken from Clear Creek at Savoy, Washington County, Arkansas. All fish had their gill, gallbladder, fins, integument, musculature, and other major organs examined for myxozoans. The gill of 1 of 34 (3%) L. cyanellus was infected with a new myxozoan, Myxobolus fergusoni n. sp. Qualitative and quantitative morphological data were obtained from fresh myxospores, and molecular data consisted of a 1,933-base-pair sequence of the partial small subunit (SSU) ribosomal RNA (rRNA) gene. Phylogenetic analysis grouped M. fergusoni n. sp. with other centrarchid-infecting myxobolids from North America and placed this cluster in a larger clade comprising myxozoans that infect North American and European esocids, a North American aphredoderid, European percids, and a gasterosteid from Japan. Myxobolus fergusoni n. sp. infects the gill arches of L. cyanellus, similar to Myxobolus cartilaginis (Hoffman, Putz, and Dunbar, 1965), which was described from head cartilage, gill arches, and large fin rays of L. cyanellus. Another is Myxobolus mesentericusKudo, 1920, which was described from the viscera of green sunfish. A large polysporic plasmodium filled with myxospores was present in a basifilamental location associated with multiple gill filaments at their junction with the gill arch. The intact plasmodium replaced connective tissue within the arch but elicited only mild proliferation of overlying epithelium and a minimal host inflammatory response. This is the third time a myxozoan has been described from L. cyanellus, as well as being the first time it has been described from an Arkansas specimen.

Association of microbial community structure with gill disease in marine-stage farmed Atlantic salmon (Salmo salar); a yearlong study.

BACKGROUND: Understanding the relationship between resident microbiota and disease in cultured fish represents an important and emerging area of study. Marine gill disorders in particular are considered an important challenge to Atlantic salmon (Salmo salar) aquaculture, however relatively little is known regarding the role resident gill microbiota might play in providing protection from or potentiating different gill diseases. Here, 16S rRNA sequencing was used to examine the gill microbiome alongside fish health screening in farmed Atlantic salmon. Results were used to explore the relationship between microbial communities and gill disease. RESULTS: Microbial community restructuring was observed throughout the sampling period and linked to varied drivers of change, including environmental conditions and severity of gill pathology. Taxa with significantly greater relative abundance on healthier gills included isolates within genus Shewanella, and taxa within family Procabacteriaceae. In contrast, altered abundance of Candidatus Branchiomonas and Rubritalea spp. were associated with damaged gills. Interestingly, more general changes in community richness and diversity were not associated with altered gill health, and thus not apparently deleterious to fish. Gross and histological gill scoring demonstrated seasonal shifts in gill pathology, with increased severity of gill damage in autumn. Specific infectious causes that contributed to observed pathology within the population included the gill disorder amoebic gill disease (AGD), however due to the uncontrolled nature of this study and likely mixed contribution of various causes of gill disease to observed pathology results do not strongly support an association between the microbial community and specific infectious or non-infectious drivers of gill pathology. CONCLUSIONS: Results suggest that the microbial community of farmed Atlantic salmon gills undergo continual restructuring in the marine environment, with mixed influences upon this change including environmental, host, and pathogenic factors. A significant association of specific taxa with different gill health states suggests these taxa might make meaningful indicators of gill health. Further research with more frequent sampling and deliberate manipulation of gills would provide important advancement of knowledge in this area. Overall, although much is still to be learnt regarding what constitutes a healthy or maladapted gill microbial community, the results of this study provide clear advancement of the field, providing new insight into the microbial community structure of gills during an annual production cycle of marine-stage farmed Atlantic salmon.

Effect of vitamin E on energy metabolism indicators and gill tissue structure of crucian carp (Carassius auratus) under cooling stress.

The aim of this work is to examine the effects of vitamin E addition to water on the structure of the gill tissue and energy metabolism of crucian carp (Carassius auratus) under cooling stress. The crucian carp were chilled using a cold acclimation intelligent chilling equipment from 20 °C to 5 °C. They were divided into three groups: the control group (E1), the negative control group (E2), and the 100 mg/L vitamin E (E3) solution. Three different temperature points (20 °C, 10 °C, and 5 °C) were used to collect, test, and analyze the samples. The findings demonstrated that in the E3 treatment group, phosphoenolpyruvate carboxykinase, acetyl coenzyme A carboxylase, total cholesterol, urea nitrogen, triglyceride, and fatty acid synthase contents were significantly lower under cooling stress than those in the E1 and E2 treatment groups (P < 0.05). The E3 therapy group had significantly greater blood glucose, glycogen, and glycogen synthase levels than the E1 and E2 treatment groups (P < 0.05). The levels of pyruvate kinase in the E1, E2, and E3 treatment groups did not differ significantly. Crucian carp's gill tissue changed under cooling stress, including capillary dilatation, and the E3 treatment group experienced less damage overall than the E1 and E2 treatment groups. In conclusion, supplementing water with vitamin E to treat crucian carp can decrease damage, improve the body's ability to withstand cold, and slow down the stress response brought on by cooling stress. This provides a theoretical basis for supplementing water with vitamin E to fish stress relief.

Integrated histological, physiological, and transcriptome analysis reveals the post-exposure recovery mechanism of nitrite in Litopenaeus vannamei.

Nitrite is one of the most common toxic pollutants in intensive aquaculture and is harmful to aquatic animals. Recovery mechanisms post exposure to nitrite in shrimp have rarely been investigated. This study focuses on the effect of nitrite exposure and post-exposure recovery on the histological and physiological aspects of Litopenaeus vannamei and utilizes transcriptome sequencing to analyze the molecular mechanisms of adaptation to nitrite exposure. The results showed that histopathological damage to the hepatopancreas and gills caused by short-term nitrite exposure resolved with recovery. The total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and catalase (CAT) of shrimp were significantly reduced during nitrite exposure and returned to the control level after recovery, malondialdehyde (MDA) levels were opposite to them. Restoration of the antioxidant system after exposure mitigated oxidative damage. Nitrite exposure results in reduced activity of the immuno-enzymes acid phosphatase (ACP) and alkaline phosphatase (AKP), which can be recovered to the control level. L. vannamei can adapt to nitrite exposure by regulating Na+/K+-ATPase (NKA) activity. Transcriptome analysis revealed that activation of glutathione metabolism and peroxisomal pathways facilitated the mitigation of oxidative damage in L. vannamei during the recovery period. Excessive oxidative damage activates the apoptosis and p53 pathways. Additionally, Sestrin2 and STEAP4 may have a positive effect on recovery in shrimp. These results provide evidence for the damage caused by nitrite exposure and the recovery ability of L. vannamei. This study can complement the knowledge of the mechanisms of adaptation and recovery of shrimp under nitrite exposure.

Investigating the impact of chlorine dioxide in shrimp-rearing water on the stomach microbiome, gill transcriptome, and infection-related mortality in shrimp.

AIMS: This study aimed to assess the effects of chlorine dioxide (ClO2) in water on whiteleg shrimp Penaeus vannamei, evaluating its impact on the stomach microbiota, gill transcriptome, and pathogens. METHODS AND RESULTS: ClO2 was added to the aquarium tanks containing the shrimp. The application of ClO2 to rearing water was lethal to shrimp at concentrations above 1.2 ppm. On the other hand, most of the shrimp survived at 1.0 ppm of ClO2. Microbiome analysis showed that ClO2 administration at 1.0 ppm significantly reduced the α-diversity of bacterial community composition in the shrimp stomach, and this condition persisted for at least 7 days. Transcriptome analysis of shrimp gill revealed that ClO2 treatment caused massive change of the gene expression profile, including stress response genes. However, after 7 days of the treatment, the gene expression profile was similar to that of shrimp in the untreated control group, suggesting a recovery to the normal state. This 1.0-ppm ClO2 significantly reduced shrimp mortality in artificial challenges with an acute hepatopancreatic necrosis disease-causing Vibrio parahaemolyticus and white spot syndrome virus, which were added to rearing water. CONCLUSIONS: The use of ClO2 at appropriate concentrations effectively eliminates a significant portion of the bacteria in the shrimp stomach and pathogens in the water. The results of this study provide fundamental knowledge on the disinfection of pathogens in water using ClO2 and the creation of semi germ-free shrimp, which has significantly decreased microbiome in the stomach.