HEALTH MONITORING: FISH
Barber I. (1997): A non‐invasive morphometric technique for estimating cestode plerocercoid burden in small freshwater fish. Journal of Fish Biology 51: 654-658.
FULL TEXT
Abstract
A non-invasive morphometric technique is presented which can be used to predict the infection status and the proportion of infected fish weight contributed by parasite tissue in three-spined sticklebacks Gasterosteus aculeatus infected with plerocercoids of Schistocephalus solidus (Cestoda: Pseudophyllidea).
Lai Y. T., Taskinen J., Kekäläinen J., Kortet R. (2012): Non-invasive diagnosis for Philometra ovata (Nematoda) infection in the common minnow Phoxinus phoxinus. Parasitology Research 111: 2411-2418.
FULL TEXT
Abstract
Non-invasive diagnoses for most of the extraintestinal helminth infections among vertebrates are rare. In the present study, we developed and tested a non-invasive visual diagnosis method to detect the infection of the nematode Philometra ovata, which is parasitising in the body cavity of the common minnow Phoxinus phoxinus. By observing the surface of minnow’s abdomen, we diagnosed infected minnows with irregular or vermiform-shaped uplifts as a consequence of the presence of P. ovata in the body cavity. We conducted the diagnosis in minnows with or without anaesthetisation, and our results showed the non-invasive method is highly reliable (correct rate of diagnoses > 95 %) in both anaesthetised and non-anaesthetised groups. The correct rate of diagnoses in truly uninfected fish (i.e. specificity) was nearly 100 % in both groups, while the correct rate of diagnoses in truly infected fish (i.e. sensitivity) was 71 and 65 % in anaesthetised and non-anaesthetised fish, respectively. The correct rate in fish diagnosed as infected or uninfected (i.e. positive or negative predictive power) of non-invasive diagnosis was nearly 100 % among the anaesthetised fish, and over 95 % in non-anaesthetised group. The diagnosis also yielded prevalence of P. ovata infection similar to the real prevalence in anaesthetised fish. Diagnoses conducted by an inexperienced observer indicated that the method is repeatable. Taken together, the present non-invasive method seems to be a promising new tool for non-invasive detection of P. ovata infections in minnows and probably can be applied for the detection of other body cavity dwelling metazoan parasites in various host taxa.
Sanahuja I., Ibarz A. (2015): Skin mucus proteome of gilthead sea bream: a non-invasive method to screen for welfare indicators. Fish and Shellfish Immunology 46: 426-435.
FULL TEXT
Abstract
In teleosts, the skin mucus is the first physical barrier against physical and chemical attacks. It contains components related to metabolism, environmental influences and nutritional status. Here, we study mucus and composition based on a proteome map of soluble epidermal mucus proteins obtained by 2D-electrophoresis in gilthead sea bream, Sparus aurata. Over 1300 spots were recorded and the 100 most abundant were further analysed by LC-MS/MS and identified by database retrieval; we also established the related specific biological processes by Gene Ontology enrichment. Sixty-two different proteins were identified and classified in 12 GO-groups and into three main functions: structural, metabolic and protection-related. Several of the proteins can be used as targets to determine fish physiological status: actins and keratins, and especially their catabolic products, in the structural functional group; glycolytic enzymes and ubiquitin/proteasome-related proteins in the metabolic functional group; and heat shock proteins, transferrin and hemopexins, in the protection-related group. This study analyses fish mucus, a potential non-invasive tool for characterising fish status, beyond defence capacities, and we postulate some putative candidates for future studies along similar lines.
Dzul-Caamal R., Olivares-Rubio H. F., Salazar-Coria L., Rocha-Gómez M. A., Vega-López A. (2016): Multivariate analysis of biochemical responses using non-invasive methods to evaluate the health status of the endangered blackfin goodeid (Girardinichthys viviparus). Ecological Indicators 60: 1118-1129.
FULL TEXT
Abstract
The study of endangered fish species is quite a complex process that involves, in the worst case, the sacrifice of specimens. To solve this ethical problem, some laboratory studies have been conducted in the skin mucus layer (SML) on fish species with valuable results. However, to date research evaluating a panel of biomarkers in the SML of wild fish does not exist. In the current study we assessed the effects of pollutants (E1, E2, E3, EE2, BPA, NP, OP, Cu, Fe, Mn, Pb, Zn, C10H8, C16H10, C18H12, B[a]P C20H12, B[k]F C20H12, C22H12) upon a panel of biomarkers [O2, H2O2, lipid peroxidation (as TBARS), carbonyl proteins (RC=O), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), vitellogenin (VTG) and metallothionein (MT)] evaluated in the SML of the wild endangered Girardinichthys viviparus inhabiting two polluted lakes in Mexico Valley. Possible relationships were analyzed by principal components analysis (PCA) and redundancy analysis (RDA). The main finding was a clear induction of pro-oxidant forces (ROS) in the SML, probably related to biotransformation of estrogenic and phenolic compounds, in addtion to a redox process of Cu and Fe. As a consequence, oxidative tissue damage (TBARS and RC=O) and increases in antioxidant defenses were observed. In male fish, VTG was associated with bisphenol A (BPA) apparently potentiated by Cu and Fe water concentrations; meanwhile, in female fish VTG was linked to estrogens. By PCA, MT was correlated with Fe and Cu; however, it was not linked with diminution of oxidative stress. For the first time have demonstrated the useful of the SML using a panel of biomarkers for monitoring the health of wild fish.
Carda-Diéguez M., Ghai R., Rodríguez-Valera F., Amaro C. (2017): Wild eel microbiome reveals that skin mucus of fish could be a natural niche for aquatic mucosal pathogen evolution. Microbiome 5: 162.
FULL TEXT
Abstract
Fish skin mucosal surfaces (SMS) are quite similar in composition and function to some mammalian MS and, in consequence, could constitute an adequate niche for the evolution of mucosal aquatic pathogens in natural environments. We aimed to test this hypothesis by searching for metagenomic and genomic evidences in the SMS-microbiome of a model fish species (Anguilla anguilla or eel), from different ecosystems (four natural environments of different water salinity and one eel farm) as well as the water microbiome (W-microbiome) surrounding the host. Remarkably, potentially pathogenic Vibrio monopolized wild eel SMS-microbiome from natural ecosystems, Vibrio anguillarum/Vibrio vulnificus and Vibrio cholerae/Vibrio metoecus being the most abundant ones in SMS from estuary and lake, respectively. Functions encoded in the SMS-microbiome differed significantly from those in the W-microbiome and allowed us to predict that successful mucus colonizers should have specific genes for (i) attachment (mainly by forming biofilms), (ii) bacterial competence and communication, and (iii) resistance to mucosal innate immunity, predators (amoeba), and heavy metals/drugs. In addition, we found several mobile genetic elements (mainly integrative conjugative elements) as well as a series of evidences suggesting that bacteria exchange DNA in SMS. Further, we isolated and sequenced a V. metoecus strain from SMS. This isolate shares pathogenicity islands with V. cholerae O1 from intestinal infections that are absent in the rest of sequenced V. metoecus strains, all of them from water and extra-intestinal infections. We have obtained metagenomic and genomic evidence in favor of the hypothesis on the role of fish mucosal surfaces as a specialized habitat selecting microbes capable of colonizing and persisting on other comparable mucosal surfaces, e.g., the human intestine.
Fernández-Alacid L., Sanahuja I., Ordóñez-Grande B., Sánchez-Nuño S., Viscor G., Gisbert E., Herrera M., Ibarz A. (2018): Skin mucus metabolites in response to physiological challenges: A valuable non-invasive method to study teleost marine species. Science of the Total Environment 644: 1323-1335.
FULL TEXT
Abstract
Knowledge concerning the health and welfare of fish is important to conserve species diversity. Fish mucosal surfaces, and particularly the skin, are of utmost importance to protect the integrity and homeostasis of the body and to prevent skin infections by pathogens. We performed three trials simulating different environmental and anthropogenic challenges: fish capture (air exposure), bacterial infection and fasting, with the aim of evaluating epidermal mucus as a non-invasive target of studies in fish. In this initial approach, we selected three well-known marine species: meagre (Argyrosomus regius), European sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) for our study. Mucus viscosity was measured in order to determine its rheological properties, and mucus metabolite (glucose, lactate, protein and cortisol) levels were analysed to establish their suitability as potential biomarkers. Skin mucus appeared as a viscous fluid exhibiting clearly non-Newtonian behaviour, with its viscosity being dependent on shear rate. The highest viscosity (p < 0.05) was observed in sea bream. Mucus metabolites composition responded to the different challenges. In particular, glucose increased significantly due to the air exposure challenge in meagre; and it decreased during food deprivation in sea bream by a half (p < 0.05). In contrast, mucus protein only decreased significantly after pathogenic bacterial infection in sea bass. In addition, mucus lactate immediately reflected changes closely related to an anaerobic condition; whereas cortisol was only modified by air exposure, doubling its mucus concentration (p < 0.05). The data provided herein demonstrate that mucus metabolites can be considered as good non-invasive biomarkers for evaluating fish physiological responses; with the glucose/protein ratio being the most valuable and reliable parameter. Determining these skin mucus metabolites and ratios will be very useful when studying the condition of critically threatened species whose conservation status prohibits the killing of specimens.
Fossøy F., Brandsegg H., Sivertsgård R., Pettersen O., Sandercock B. K., Solem Ø., Hindar K., Mo T. A. (2020): Monitoring presence and abundance of two gyrodactylid ectoparasites and their salmonid hosts using environmental DNA. Environmental DNA 2: 53-62.
FULL TEXT
Abstract
Invasive species represent a major challenge for the conservation of biodiversity. The invasive ectoparasitic fluke Gyrodactylus salaris is considered one of the major threats to the Atlantic salmon (Salmo salar), and the parasite has so far been detected in 50 rivers in Norway. We investigate environmental DNA (eDNA) as a tool for detecting and assessing relative abundance of G. salaris and Atlantic salmon, upstream and downstream of a recently constructed artificial migration barrier in the River Driva in Norway. In addition, we also use eDNA to assess abundance of the less pathogenic G. derjavinoides and its main host, the brown trout (S. trutta). We filtered 1 L and 10 L of water through a 0.45 μm cellulose filter and a 2.0 μm glass fiber filter, respectively, at nine different localities along the river. Concentrations of eDNA were assessed using droplet digital PCR (ddPCR) and compared to parasite abundance based on conventional methodology using electrofishing and the counting of individual parasites on juvenile salmon. All four species could successfully be detected from water samples using two different protocols varying in sample volumes, filter types, and DNA-isolation methods. However, eDNA-occupancy modeling revealed that the probability of detecting the two gyrodactylid species was higher when filtering 10 L water through a 2.0 μm glass fiber filter (p > .99) than when filtering 1 L water through a 0.45 μm cellulose filter (p = .48–.78). The eDNA concentrations of the two fish species were markedly higher below the migration barrier, reflecting the expected higher biomass of fish. For the two gyrodactylid parasites, eDNA concentrations showed a peak upstream of the migration barrier and decreased below the migration barrier. The observed pattern was consistent with parasite abundance based on conventional methodology. Assessing abundance in rivers using eDNA is challenging and potentially influenced by downstream accumulation and dilution from tributaries, but our results suggest that G. salaris eDNA concentrations were indicative of parasite abundance. We conclude that eDNA is an efficient way of monitoring gyrodactylid parasites and their salmonid hosts, and we suggest that eDNA should be incorporated into future monitoring of G. salaris.
Duval E., Blanchet S., Quéméré E., Jacquin L., Veyssière C., Lautraite A., Garmendia L., Yotte A., Parthuisot N., Côte J., Loot G. (2021): Urine DNA (uDNA) as a non‐lethal method for endoparasite biomonitoring: development and validation. Environmental DNA 3: 1035-1045.
FULL TEXT
Abstract
Changes in environmental conditions alter host–parasite interactions, raising the need for effective epidemiological surveillance. Developing operational, accurate, and cost-effective methods to assess individual infection status and potential for pathogen spread is a prerequisite to anticipate future disease outbreaks in wild populations. For endoparasites, effective detection of infections usually relies on host-lethal approaches, which are barely compatible with wildlife conservation objectives. Here, we used the brown trout (Salmo trutta)—Tetracapsuloides bryosalmonae host–parasite system to develop a non-lethal method for endoparasite infection detection, hereafter called “uDNA” for urine DNA. The uDNA diagnostic test is based on the amplification of endoparasite DNA from host urine. We sampled wild fish (N = 111) from eight sites, let them excrete in individual buckets filled with mineral water and performed parasite DNA amplification from water filtration. We compared the results of the uDNA diagnostic test for host infection status and parasite load to those from kidney samples (the current standard method). uDNA was sensitive in determining host infection status (even for infected hosts showing no sign of the disease), since up to 90% of fish individuals were correctly assigned to their infection status. The quantity of uDNA detected from the hosts depended on the sampling sites, suggesting a spatial variation in the parasite spread. uDNA was positively, but weakly correlated with parasite load in the kidney. This correlation depended on the severity of macroscopic lesions caused by the disease and was negative in fish with severely damaged kidney, likely due to impaired urine excretion. The uDNA approach provides novel avenues to non-lethally infer infection parameters from wildlife populations at large spatial scales. By targeting parasite transmission stage, uDNA is also valuable to get insights on the parasite fitness and the ecological and evolutionary dynamics of this host–parasite interaction.
Ivanova L., Rangel-Huerta O. D., Tartor H., Gjessing M. C., Dahle M. K., Uhlig S. (2022): Fish skin and gill mucus: a source of metabolites for non-invasive health monitoring and research. Metabolites 12: 28.
FULL TEXT
Abstract
Mucous membranes such as the gill and skin mucosa in fish protect them against a multitude of environmental factors. At the same time, changes in the molecular composition of mucus may provide valuable information about the interaction of the fish with their environment, as well as their health and welfare. In this study, the metabolite profiles of the plasma, skin and gill mucus of freshwater Atlantic salmon (Salmo salar) were compared using liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). Several normalization procedures aimed to reduce unwanted variation in the untargeted data were tested. In addition, the basal metabolism of skin and gills, and the impact of the anesthetic benzocaine for euthanisation were studied. For targeted metabolomics, the commercial AbsoluteIDQ p400 HR kit was used to evaluate the potential differences in metabolic composition in epidermal mucus as compared to the plasma. The targeted metabolomics data showed a high level of correlation between different types of biological fluids from the same individual, indicating that mucus metabolite composition could be used for fish health monitoring and research.
Pratte Z. A., Perry C., Dove A. D., Hoopes L. A., Ritchie K. B., Hueter R. E., Fischer C., Newton A. L., Stewart F. J. (2022): Microbiome structure in large pelagic sharks with distinct feeding ecologies. Animal Microbiome 4: 17.
FULL TEXT
Abstract
Sharks play essential roles in ocean food webs and human culture, but also face population declines worldwide due to human activity. The relationship between sharks and the microbes on and in the shark body is unclear, despite research on other animals showing the microbiome as intertwined with host physiology, immunity, and ecology. Research on shark-microbe interactions faces the significant challenge of sampling the largest and most elusive shark species. We leveraged a unique sampling infrastructure to compare the microbiomes of two apex predators, the white (Carcharodon carcharias) and tiger shark (Galeocerdo cuvier), to those of the filter-feeding whale shark (Rhincodon typus), allowing us to explore the effects of feeding mode on intestinal microbiome diversity and metabolic function, and environmental exposure on the diversity of microbes external to the body (on the skin, gill). The fecal microbiomes of white and whale sharks were highly similar in taxonomic and gene category composition despite differences in host feeding mode and diet. Fecal microbiomes from these species were also taxon-poor compared to those of many other vertebrates and were more similar to those of predatory teleost fishes and toothed whales than to those of filter-feeding baleen whales. In contrast, microbiomes of external body niches were taxon-rich and significantly influenced by diversity in the water column microbiome. These results suggest complex roles for host identity, diet, and environmental exposure in structuring the shark microbiome and identify a small, but conserved, number of intestinal microbial taxa as potential contributors to shark physiology.
Strike E. M., Harris J. L., Ballard K. L., Hawkins J. P., Crockett J., Stevens G. M. (2022): Sublethal injuries and physical abnormalities in Maldives manta rays, Mobula alfredi and M. birostris. Frontiers in Marine Science 9: 773897.
FULL TEXT
Abstract
Manta ray populations worldwide are vulnerable to sublethal injuries resulting from human activities, e.g., entanglement in fishing line and boat strikes, which have the potential to impact an individual’s health, fitness, and behaviour. Sublethal injuries and physical abnormalities also occur naturally from predation events, deformity, parasites, and disease. To determine the type and frequency of anthropogenic and natural originated injury events affecting Mobula alfredi and M. birostris in the Maldives, we examined data from the Manta Trust’s Maldivian Manta Ray Project (MMRP) database, which contains 73,638 photo-identification (photo-ID) sightings of the two manta ray species from 1987 to 2019. The likely origin of each injury or physical abnormality was determined based on visual assessment of the photo-ID images. Multiple injuries to an individual originating from the same event were grouped for analysis. Generalised linear mixed models (GLMM) were used to investigate the relationship between the occurrence of injury events and the explanatory variables sex and maturity status for both species, with the additional variable site function (cleaning, feeding, cruising) investigated for M. alfredi. Spatial and temporal variations in M. alfredi injury events, and their origin and type, were investigated by calculating the percentage of injury events per sighted individual at each Maldivian atoll, and per re-sighted individual in each year from 2005 to 2019. For both species, injury events were predominantly of natural origin, with predatory bites being the most frequent type. The most common anthropogenic injury type was entanglement in fishing line. Injuries to M. alfredi were significantly more likely to be observed on juveniles than adults, males than females, and at cleaning stations as opposed to feeding or cruising sites. Neither sex nor maturity status were significant explanatory variables for the occurrence of injuries to M. birostris. Highest percentages of anthropogenic injuries per sighted M. alfredi were recorded in North Malé, South Malé, Baa, Addu, and Laamu Atolls, where boat traffic, fishing, and tourism activities are concentrated. Overall, this work greatly improves understanding of the sublethal threats faced by manta rays in the Maldives; identifying focus areas where conservation management actions are required to ensure more effective protection of this threatened species group.
Coutinho C. D., Ford C. E., Trafford J. D., Duarte A., Rebelo R., Rosa G. M. (2023): Non-lethal detection of Ranavirus in fish. Viruses 15: 471.
FULL TEXT
Abstract
Emergent infectious diseases have an increasing impact on both farmed animals and wildlife. The ability to screen for pathogens is critical for understanding host–pathogen dynamics and informing better management. Ranavirus is a pathogen of concern, associated with disease outbreaks worldwide, affecting a broad range of fish, amphibian, and reptile hosts, but research has been limited. The traditional screening of internal tissues, such as the liver, has been regarded as the most effective for detecting and quantifying Ranavirus. However, such methodology imposes several limitations from ethical and conservation standpoints. Non-lethal sampling methods of viral detection were explored by comparing the efficacy of both buccal swabbing and fin clipping. The study was conducted on two Iberian, threatened freshwater fish (Iberochondrostoma lusitanicum and Cobitis paludica), and all samples were screened using qPCR. While for C. paludica both methods were reliable in detecting Ranavirus, on I. lusitanicum, there was a significantly higher detection rate in buccal swabs than in fin tissue. This study, therefore, reports that fin clipping may yield false Ranavirus negatives when in small-bodied freshwater fish. Overall, buccal swabbing is found to be good as an alternative to more invasive procedures, which is of extreme relevance, particularly when dealing with a threatened species.
Froman N., Genain M. A., Stevens G. M., Pearce G. P. (2023): Use of underwater contactless ultrasonography to elucidate the internal anatomy and reproductive activity of manta and devil rays (Fam. Mobulidae). Journal of Fish Biology.
FULL TEXT
Abstract
The ability to visualise the internal anatomical structures of fish provides important information on their reproductive status and body condition and has made important contributions to many areas of fish biology. Obtaining information about the internal anatomy of fish has traditionally required euthanasia and dissection. However, although ultrasonography is now increasingly used to study internal fish anatomy without the need for euthanasia, traditional techniques still require restraint and contact with the animal, both of which are known to cause stress. This has prompted the development of waterproof, contactless, and portable equipment to allow ultrasonographic examinations to be carried out in free-swimming individuals which also facilitates the application of this tool in wild populations of endangered species. This study reports the validation of this equipment using anatomical examinations of nine manta and devil ray (Mobulidae) specimens landed at fish markets in Sri Lanka. Species studied were Mobula kuhlii (n = 3), M. thurstoni (n = 1), M. mobular (n = 1), M. tarapacana (n = 1) and M. birostris (n = 3). The use of this equipment was further validated with ultrasonographic examinations in 55 free-swimming reef manta rays Mobula alfredi, which enabled maturity status to be quantified in 32 females. Structures successfully identified in free-swimming individuals were the liver, spleen, gallbladder, gastrointestinal tract, skeletal structures, developing follicles and uterus. The study demonstrated that ultrasonography provided a reliable method of determining both sexual maturity and gestational status in free-swimming M. alfredi. The methodology induced no detectable signs of disturbance to the animals involved and therefore offers a viable and practical alternative to invasive techniques currently used to study anatomical changes in both captive and wild marine organisms.