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The need to find sustainable food sources to feed the growing population makes the utilization of all available food resources especially important. But introducing new food is challenging and often fails. In the consumer behavior literature, food neophobia (FN), the unwillingness to try new food, has been identified as a crucial factor in understanding the adoption of new food products. However, limited research can be found on the role of FN in industrial buyers' choice of new food products. Industrial buyers are important gatekeepers for the introduction of new food products as they decide what is offered to the consumers and may stop any market entry long before a new food product reaches the consumers' attention. Thus, the understanding of the potential FN in industrial buying behavior, in different markets, is important to succeed with the introduction of new food products. In this study, we have explored FN as a potential barrier to the adoption of a new seafood product, farmed lumpfish (Cyclopterus lumpus), by industrial buyers in South Korea and Vietnam. The results revealed differences between the two countries' industrial buyers, with South Koreans demonstrating more FN than the Vietnamese. This contradicts with the consumer research showing that FN decreases with increased income, education, and urbanization. [ABSTRACT FROM AUTHOR]

Lumpfish (Cyclopterus lumpus) are used as cleaner fish in Atlantic salmon (Salmo salar) aquaculture as one of multiple control measures against salmon lice (Lepeophtheirus salmonis). Numerous studies have documented weight as an important factor for characterising the cleaning efficacy of individual lumpfish. Hence, the efficacy of lumpfish in fish farms depends on the size at stocking and the weight development over time. Here, we aimed to quantify how weight developed over time for lumpfish deployed in salmon farming sea cages in Norway through modelling the daily growth rate. We found that the coefficient of variation for lumpfish weight increased over time, implying that the standard deviation increased more than the expected weight. The data thus showed heterogeneous growth for lumpfish in salmon farming cages, where some individuals exhibited no apparent growth, and others significant proliferation. We found that the daily growth rate was best described as bell-shaped functions of weight and temperature, consistent with a sigmoid-shaped growth curve and an optimal temperature around 10 °C. These results allow for more realistic modelling of the efficacy of lumpfish in controlling salmon lice in fish farms, as one can combine estimates of weight-dependent cleaning efficacy with weight development over time. [ABSTRACT FROM AUTHOR]

In this study, we explored the effects of chronic stress on lumpfish (Cyclopterus lumpus) physiological, immune response, health, and plasma free amino acids. 3 groups of lumpfish were exposed to 1-minute air exposure. 1 group was exposed to stress once per week, a second group exposed 2 times per week, and a third group exposed 4 times per week. The present study revealed significant alterations in immunity and increased nutritional demands, particularly the branched chain amino acids and lysine. Cortisol levels fluctuated, with significantly higher levels halfway through the experiment on the groups that were stressed more often. Though, by the end of the experiment, there were no significant differences in cortisol levels between groups. Regardless of stress exposure, cataract developed in virtually all sampled fish, pointing toward a potential dietary imbalance. A transient immunomodulation of stress was visible. While in early stages stress had an immune enhancing effect, as seen by the increase in plasma nitric oxide and peroxidase in the group most frequently exposed to stress, these differences were not apparent by the end of the experiment. Additionally, the worst health condition was found in this group. Our results underscore the complex interplay between stress, immunity and nutrition, highlighting the need for tailored dietary strategies and improved rearing practices. [ABSTRACT FROM AUTHOR]

Lumpfish (Cyclopterus lumpus) have become the predominant cleaner fish species used in North American salmon aquaculture. Vibrio anguillarum is a frequent pathogen of lumpfish in Atlantic Canada, and current vaccines against local isolates conferred low to moderate efficacy. This study evaluated the safety and efficiency of a V. anguillarum autogenous vaccine under controlled and field conditions. Two safety trials were conducted following the Canadian Food Inspection Agency (CFIA) regulations before field trial testing. The first safety trial was a common garden assay, and 250 PIT-tsgged lumpfish were used for five treatments per tank (PBS-negative control, Lab vaccine-positive control, autogenous intraperitoneal (IP) vaccine, autogenous dip vaccine, autogenous dip-IP boosted vaccine) in triplicates. Weight, gross pathology, and IgM titers were evaluated to determine the vaccine's safety. After 10 weeks postvaccination (wpv), lumpfish were bath-challenged with a lethal dose (1.24 x 106 CFU/mL) of V. anguillarum serotype O2. Survival rate, IgM titers, memory immune response, and cross-immune protection were evaluated. The second safety trial was conducted using a double vaccine dose in two groups, PBS and autogenous IP. The gross pathology score indicated a normal immune response without tissue damage, and no mortality nor fish health issues were observed in the immunized animals. The IP route of administration conferred the highest protection against the V. anguillarum challenge. The autogenous vaccine conferred long-term immunity but did not confer cross-protection against V. anguillarum serotype O1. To evaluate the efficiency of the autogenous vaccine under field conditions, 58,976 naïve lumpfish (8-10 g) were IP immunized with either the autogenous vaccine or the commercial Forte micro IV vaccine. After 7 wpv, the lumpfish were equally distributed into eight sea cages and co-cultivated with Atlantic salmon smolts (60,000 per cage). Lumpfish IgM titers, tissue bacterial loads, mortality, and sea lice count on salmon were monitored. The autogenous vaccine and Forte vaccine confer acceptable protection to the lumpfish in sea cages. No significant difference was observed between lumpfish vaccinated with autogenous and commercial vaccines under field conditions. [ABSTRACT FROM AUTHOR]

The Gulf of Maine (GoM) is one of the fastest-warming parts of the world's oceans. Some species' distributional shifts have already been documented, especially for commercially-important species. Less is known about species that are not currently exploited but may become so in the future. As a case study into these issues, we focus on lumpfish (Cyclopterus lumpus) because of the recognized and timely need to understand wild lumpfish population dynamics to support sustainable fisheries and aquaculture developments. Using occurrence data from five different fisheries-dependent and independent surveys, we examined lumpfish distribution over time in the GoM. We found that lumpfish presence was more likely in Fall and correlated with deeper waters and colder bottom temperatures. Since 1980, lumpfish presence has increased over time and shifted north. Given a limited set of data, these findings should be interpreted with caution as additional work is needed to assess if the actual distribution of lumpfish is changing. Nevertheless, our work provides preliminary information for resource managers to ensure that lumpfish are harvested sustainably for use in emergent lumpfish aquaculture facilities. [ABSTRACT FROM AUTHOR]

Background: Both bacterial and viral diseases are a major threat to farmed fish. As the antiviral immune mechanisms in lumpfish (Cyclopterus lumpus L.) are poorly understood, lumpfish leukocytes were stimulated with poly(I:C), a synthetic analog of double stranded RNA, which mimic viral infections, and RNA sequencing was performed. Methods: To address this gap, we stimulated lumpfish leukocytes with poly(I:C) for 6 and 24 hours and did RNA sequencing with three parallels per timepoint. Genome guided mapping was performed to define differentially expressed genes (DEGs). Results: Immune genes were identified, and transcriptome-wide analyses of early immune responses showed that 376 and 2372 transcripts were significantly differentially expressed 6 and 24 hours post exposure (hpe) to poly(I:C), respectively. The most enriched GO terms when time had been accounted for, were immune system processes (GO:0002376) and immune response (GO:0006955). Analysis of DEGs showed that among the most highly upregulated genes were TLRs and genes belonging to the RIG-I signaling pathway, including LGP2, STING and MX, as well as IRF3 and IL12A. RIG-I was not identified, but in silico analyses showed that genes encoding proteins involved in pathogen recognition, cell signaling, and cytokines of the TLR and RIG-I signaling pathway are mostly conserved in lumpfish when compared to mammals and other teleost species. Conclusions: Our analyses unravel the innate immune pathways playing a major role in antiviral defense in lumpfish. The information gathered can be used in comparative studies and lay the groundwork for future functional analyses of immune and pathogenicity mechanisms. Such knowledge is also necessary for the development of immunoprophylactic measures for lumpfish, which is extensively cultivated for use as cleaner fish in the aquaculture for removal of sea lice from Atlantic salmon (Salmo salar L.). [ABSTRACT FROM AUTHOR]

Lumpfish are broadly used as biological sea lice removers in Norwegian salmon farming and are mostly produced in hatcheries. To date, there is little systematic documentation on the mortality causes of lumpfish in hatcheries. In the current study, data from 12 selected fish groups from four hatcheries in Norway were collected to understand the challenges and opportunities related to the categorization of mortality causes of lumpfish in hatcheries. This study indicated that a high proportion of lumpfish mortality was categorized by the hatcheries as unspecified. When specified, mortality was primarily assessed as due to fin damage. Our analyses showed that mortality categorized as fin damage correlated with the detection of infectious agents in dead fish, suggesting that mortality was due to infections rather than fin damage. It was not possible to conclude whether infection with pathogens present in the environment caused fin damage or if injuries from aggression were a gateway for pathogens. Furthermore, due to the lack of information regarding production conditions, it was not possible to assess risk factors causing eventual aggression or the presence of pathogens. This study revealed that mortality causality—the chain of events leading to death—is mainly unclear in lumpfish hatcheries because (1) mortality categorization does not focus on underlying causes and (2) there is little documentation of production conditions, making it very difficult to relate mortality rates to external factors. The present findings highlight that there are gaps in the registrations made by hatcheries and that there is an urgent need to implement standardized monitoring protocols for lumpfish hatcheries. This will help identify the causes of mortality and, therefore, allow for the implementation of proper measures that will ensure better survival. [ABSTRACT FROM AUTHOR]

Aeromonas salmonicida, a widely distributed aquatic pathogen causing furunculosis in fish, exhibits varied virulence, posing challenges in infectious disease and immunity studies, notably in vaccine efficacy assessment. Lumpfish (Cyclopterus lumpus) has become a valuable model for marine pathogenesis studies. This study evaluated several antigen preparations against A. salmonicida J223, a hypervirulent strain of teleost fish, including lumpfish. The potential immune protective effect of A. salmonicida bacterins in the presence and absence of the A‐layer and extracellular products was tested in lumpfish. Also, we evaluated the impact of A. salmonicida outer membrane proteins (OMPs) and iron‐regulated outer membrane proteins (IROMPs) on lumpfish immunity. The immunized lumpfish were intraperitoneally (i.p.) challenged with 104A. salmonicida cells/dose at 8 weeks‐post immunization (wpi). Immunized and non‐immunized fish died within 2 weeks post‐challenge. Our analyses showed that immunization with A. salmonicida J223 bacterins and antigen preparations did not increase IgM titres. In addition, adaptive immunity biomarker genes (e.g., igm, mhc‐ii and cd4) were down‐regulated. These findings suggest that A. salmonicida J223 antigen preparations hinder lumpfish immunity. Notably, many fish vaccines are bacterin‐based, often lacking efficacy evaluation. This study offers crucial insights for finfish vaccine approval and regulations. [ABSTRACT FROM AUTHOR]

Lumpfish (Cyclopterus lumpus) are used as cleaner fish in salmon aquaculture to treat sea lice. However, after 18–24 months and reaching 0.4–0.6 kg, the fish is removed from the salmon cage and usually discarded, which raises social, economic, and environmental challenges, as well as ethical concerns. This paper assesses the viability of marketing lumpfish as food by exploring possible products that can be made from the fish in Vietnamese cuisine, and understanding the stakeholder's perception and acceptance of the fish. We used a customer co-creation method to investigate market potential, sending a sample of 45 kg of frozen and whole lumpfish from Norway to Vietnam. Researchers, industrial stakeholders, restaurant chefs, and household consumers collaborated to discuss, process, cook, and taste the fish, and the evaluations were assessed before and after consumption. More than 10 Vietnamese dishes were identified as possible use for lumpfish, including grilled, fried, sour soup, hotpot, and several value-added products. Household consumers and restaurant buyers evaluated the fish positively in terms of sensory quality (taste, color, flavor, size, and texture), but the rough skin and sharp thorn are negative aspects. Individual consumers accept the fish and were willing to buy it if the price is reasonable. In contrast, industrial stakeholders evaluated the lumpfish less favorably, citing its soft and mushy texture, sticky smell, and very low fillet-recovery-ratio (only 15.9% of skinless fillet and 16.7% of kama can be obtained from whole-defrosted lumpfish). They also found that the taste of the fish was not delicious and bitter in some value-added products. In addition, this study found that the information relating to lumpfish as a cleaner fish is not an issue in the Vietnamese context. [ABSTRACT FROM AUTHOR]

Lumpfish (Cyclopterus lumpus) is an underutilized marine resource that is currently only being exploited for roe. Lumpfish skin was pre-treated with alkali (0.1M NaOH) and acid (0.1M HCl) at a skin to chemical ratio of 1:10 for 24 h at 5 °C to remove non-collagenous proteins and minerals. The pre-treated skin was washed, and gelatine was extracted with 0.1M of acetic acid at three different ratios (1:5, 1:10, and 1:15), time (12,18, and 24 h), and temperature combinations (12, 28, and 24 °C). The highest total extraction yield (>40%) was obtained with combinations of extraction ratios of 1:15 and 1:10 with a longer time (24 h) and higher temperature (18–24 °C). The highest gelatine content was obtained with an extraction period of 24 h and ratio of 1:10 (>80%). SDS-PAGE analysis confirmed the presence of type-I collagen. A rheological evaluation indicated melting and gelling temperatures, gel strength, and viscosity properties comparable to existing cold-water gelatine sources. [ABSTRACT FROM AUTHOR]

In this study, we explored the effects of chronic stress on lumpfish (Cyclopterus lumpus) physiological, immune response, health, and plasma free amino acids. 3 groups of lumpfish were exposed to 1-minute air exposure. 1 group was exposed to stress once per week, a second group exposed 2 times per week, and a third group exposed 4 times per week. The present study revealed significant alterations in immunity and increased nutritional demands, particularly the branched chain amino acids and lysine. Cortisol levels fluctuated, with significantly higher levels halfway through the experiment on the groups that were stressed more often. Though, by the end of the experiment, there were no significant differences in cortisol levels between groups. Regardless of stress exposure, cataract developed in virtually all sampled fish, pointing toward a potential dietary imbalance. A transient immunomodulation of stress was visible. While in early stages stress had an immune enhancing effect, as seen by the increase in plasma nitric oxide and peroxidase in the group most frequently exposed to stress, these differences were not apparent by the end of the experiment. Additionally, the worst health condition was found in this group. Our results underscore the complex interplay between stress, immunity and nutrition, highlighting the need for tailored dietary strategies and improved rearing practices.

The Gulf of Maine (GoM) is one of the fastest-warming parts of the world’s oceans. Some species’ distributional shifts have already been documented, especially for commercially-important species. Less is known about species that are not currently exploited but may become so in the future. As a case study into these issues, we focus on lumpfish (Cyclopterus lumpus) because of the recognized and timely need to understand wild lumpfish population dynamics to support sustainable fisheries and aquaculture developments. Using occurrence data from five different fisheries-dependent and independent surveys, we examined lumpfish distribution over time in the GoM. We found that lumpfish presence was more likely in Fall and correlated with deeper waters and colder bottom temperatures. Since 1980, lumpfish presence has increased over time and shifted north. Given a limited set of data, these findings should be interpreted with caution as additional work is needed to assess if the actual distribution of lumpfish is changing. Nevertheless, our work provides preliminary information for resource managers to ensure that lumpfish are harvested sustainably for use in emergent lumpfish aquaculture facilities.

Lumpfish (Cyclopterus lumpus) are extensively used as part of the control measures against salmon lice in fish farms. In recent years, there has been an increased focus on lumpfish welfare, and how to increase survival of lumpfish during production. To survey lumpfish welfare and compare welfare between different fish farms, welfare indicators are necessary. Condition factor is an attractive welfare indicator since it depends only on the length and weight of the fish, which is easy to measure and does not require euthanisation. Fulton’s K is commonly used to assess body condition for fish. However, this condition factor assumes isometric growth, which has been found not to be a reasonable assumption for lumpfish. In this study, we suggest an alternative expression for lumpfish body condition, which is based on almost 30 000 lumpfish sampled from Norwegian fish farms during production. The resulting condition factor is given as 5.85 ⋅ W∕L2.5016, where W is the lumpfish weight measured in grams, and L is the standard length measured in centimetres. We demonstrate that our proposed condition factor is more suitable for comparing body condition of lumpfish than Fulton’s K, since Fulton’s K is negatively correlated to length such that small fish tend to have high Fulton’s K factors. We conclude that Fulton’s K is an inappropriate indicator of lumpfish welfare, and propose to rather use a condition factor tailored to lumpfish, like the presently proposed condition factor. We also illustrate why standard length (length up to the caudal fin) is more appropriate for measuring body condition than total length (i.e. length including the caudal fin). For condition based on standard length, we found that caudal fin erosion was less prevalent among the lumpfish with comparatively higher body condition. The same relationship was not found for body condition based on total length.

Rodríguez-Rey and Whittaker (Hydrobiologia 850:2089–2100, 2023, https://doi.org/10.1007/s10750-023-05220-8) recently investigated the ecological niche of lumpfish (Cyclopterus lumpus) in the Atlantic Ocean using species distribution models. They utilise occurrence records of lumpfish from the Global Biodiversity Information Facility (GBIF) and environmental data extracted from Bio-ORACLE v2.0. A premise of their analysis is that that the GBIF data reflects the relative distribution of lumpfish in the North Atlantic. However, this assumption does not hold true, as evident from the geographic imbalance observed between the GBIF samples and the data obtained from commercial fisheries for lumpfish, as well as fish surveys conducted across the North Atlantic. There is also a concern that only 11% of the individuals listed in the dataset overlapped with the time period from when environmental parameters were estimated (2000–2014). Comparing the suitability index calculated using output from the species distribution models raises concerns about its reliability as it conflicts with the actual distribution of lumpfish from survey data in the eastern Atlantic. This conflict suggests serious problems with the model, and any projections into the future should be treated with caution. [ABSTRACT FROM AUTHOR]

Simple Summary: Farmed fish are commonly exposed to stressors, which have a detrimental effect on their health and welfare. The present study explores how lumpfish, a species recognized for its potential role in alleviating the sea lice burden on farmed salmon, responds to acute stress. This is particularly important for this species, since there are concerning reports regarding their health and welfare. In our stress challenge lumpfish were exposed to air for one minute. We then examined several stress and energy metabolism biomarkers and concluded that i) lumpfish tolerates well a one-minute air exposure, and ii) cortisol is a reliable stress biomarker in this species. Our results contribute to our current understanding of how lumpfish handle a common stressor, and this knowledge is key to allow a better decision-making when it comes to welfare management in farms. This study aimed to expand knowledge on lumpfish stress physiology by investigating the effects of acute stress on primary (i.e., cortisol) and secondary (e.g., metabolites) stress responses, as well as oxidative stress biomarkers, from stress exposure to a recovery phase. The results showed that the lumpfish physiological response to 1 min air exposure is mild, in line with recent studies, and comparable to that described for white sturgeons. Cortisol seems to be the most reliable acute stress biomarker in lumpfish, with a significant increase in plasma 30 min after stress exposure, returning to resting levels 2 h after exposure. In contrast, glucose and lactate were not significantly altered by short-term air exposure. Effects on hepatic energy mobilisation were also detected following the acute stress. This study showed that acute 1 min air exposure seems tolerable, allowing a swift recovery. However, more studies on the impacts of air exposure and repeated acute stressors on lumpfish stress and immune responses are required to develop industry standards for lumpfish health and welfare monitoring. [ABSTRACT FROM AUTHOR]

Lumpfish (Cyclopterus lumpus) have become the predominant cleaner fish species used in North American salmon aquaculture. Vibrio anguillarum is a frequent pathogen of lumpfish in Atlantic Canada, and current vaccines against local isolates conferred low to moderate efficacy. This study evaluated the safety and efficiency of a V. anguillarum autogenous vaccine under controlled and field conditions. Two safety trials were conducted following the Canadian Food Inspection Agency (CFIA) regulations before field trial testing. The first safety trial was a common garden assay, and 250 PIT-tsgged lumpfish were used for five treatments per tank (PBS-negative control, Lab vaccine-positive control, autogenous intraperitoneal (IP) vaccine, autogenous dip vaccine, autogenous dip-IP boosted vaccine) in triplicates. Weight, gross pathology, and IgM titers were evaluated to determine the vaccine’s safety. After 10 weeks post-vaccination (wpv), lumpfish were bath-challenged with a lethal dose (1.24 x 106 CFU/mL) of V. anguillarum serotype O2. Survival rate, IgM titers, memory immune response, and cross-immune protection were evaluated. The second safety trial was conducted using a double vaccine dose in two groups, PBS and autogenous IP. The gross pathology score indicated a normal immune response without tissue damage, and no mortality nor fish health issues were observed in the immunized animals. The IP route of administration conferred the highest protection against the V. anguillarum challenge. The autogenous vaccine conferred long-term immunity but did not confer cross-protection against V. anguillarum serotype O1. To evaluate the efficiency of the autogenous vaccine under field conditions, 58,976 naïve lumpfish (8-10 g) were IP immunized with either the autogenous vaccine or the commercial Forte micro IV vaccine. After 7 wpv, the lumpfish were equally distributed into eight sea cages and co-cultivated with Atlantic salmon smolts (60,000 per cage). Lumpfish IgM titers, tissue bacterial loads, mortality, and sea lice count on salmon were monitored. The autogenous vaccine and Forte vaccine confer acceptable protection to the lumpfish in sea cages. No significant difference was observed between lumpfish vaccinated with autogenous and commercial vaccines under field conditions.

Background: The Janus kinase/signal transducers and activators of transcription (JAK-STAT) system regulates several biological processes by affecting transcription of genes as a response to cytokines and growth factors. In the present study, we have characterized the STAT genes in lumpfish (Cyclopterus lumpus L.), belonging to the order Perciformes, and investigated regulation of the JAK-STAT signaling pathway upon exposure to bacteria (Vibrio anguillarum) and poly(I:C), the latter mimicking antiviral responses. Methods: Characterization and evolutionary analyses of the STATs were performed by phylogeny, protein domain, homology similarity and synteny analyses. Antibacterial and antiviral responses were investigated by performing KEGG pathway analysis. Results: We observed that lumpfish have stat1a, 2, 3, 4, 5a, 5b, and 6. Transcriptome-wide analyses showed that most components of the JAK-STAT pathway were present in lumpfish. il-6, il-10, il-21, ikBa and stat3 were upregulated 6 hours post exposure (hpe) against bacteria while type I interferons (IFNs), irf1, irf3, irf10, stat1 and 2 were upregulated 24 hpe against poly(I:C). Conclusions: Our findings shed light on the diversity and evolution of the STATs and the data show that the STAT genes are highly conserved among fish, including lumpfish. The transcriptome-wide analyses lay the groundwork for future research into the functional significance of these genes in regulating critical biological processes and make an important basis for development of prophylactic measure such as vaccination, which is highly needed for lumpfish since it is vulnerable for both bacterial and viral diseases. [ABSTRACT FROM AUTHOR]

The commercial farming of juvenile lumpfish requires monitoring of gonadal development to achieve synchronized production. Conventional methods such as gonadosomatic index (GSI), sex hormone analyses, gonadal histology, endoscopy, and gene expression analyses are costly, invasive, and often involve sacrificing the fish. We assessed the efficiency of ultrasound as a non‐invasive method for monitoring gonadal development in lumpfish. Based on ultrasound observations, we categorized the fish into six stages; F0 to F5 for females and M0 to M5 for males, that represented maturity levels from immature to spent. Importantly, the ultrasound gonadal stages aligned with histological gonadal stages. Additionally, ultrasound stages aligned with profiles of GSI, testosterone (T), 11‐ketotestosterone, and 17β‐estradiol throughout gonadal development including the spawning period. Moreover, these parameters exhibited significant positive correlations with each other reflecting their parallel trends during gonadal development. To minimize the frequency of ultrasound usage and fish handling, we established F3 and M3/M4 as arbitrary thresholds for identifying ripe females and males, respectively. By using these thresholds, the need for regular ultrasound monitoring could be reduced during most of the rearing period. Ultrasound proves to be useful and reliable for monitoring gonadal development in lumpfish, enabling synchronized production of juvenile fish. [ABSTRACT FROM AUTHOR]

Background: Both bacterial and viral diseases are a major threat to farmed fish. As the antiviral immune mechanisms in lumpfish (Cyclopterus lumpus L.) are poorly understood, lumpfish leukocytes were stimulated with poly(I:C), a synthetic analog of double stranded RNA, which mimic viral infections, and RNA sequencing was performed. Methods: To address this gap, we stimulated lumpfish leukocytes with poly(I:C) for 6 and 24 hours and did RNA sequencing with three parallels per timepoint. Genome guided mapping was performed to define differentially expressed genes (DEGs). Results: Immune genes were identified, and transcriptome-wide analyses of early immune responses showed that 376 and 2372 transcripts were significantly differentially expressed 6 and 24 hours post exposure (hpe) to poly(I:C), respectively. The most enriched GO terms when time had been accounted for, were immune system processes (GO:0002376) and immune response (GO:0006955). Analysis of DEGs showed that among the most highly upregulated genes were TLRs and genes belonging to the RIG-I signaling pathway, including LGP2, STING and MX, as well as IRF3 and IL12A. RIG-I was not identified, but in silico analyses showed that genes encoding proteins involved in pathogen recognition, cell signaling, and cytokines of the TLR and RIG-I signaling pathway are mostly conserved in lumpfish when compared to mammals and other teleost species. Conclusions: Our analyses unravel the innate immune pathways playing a major role in antiviral defense in lumpfish. The information gathered can be used in comparative studies and lay the groundwork for future functional analyses of immune and pathogenicity mechanisms. Such knowledge is also necessary for the development of immunoprophylactic measures for lumpfish, which is extensively cultivated for use as cleaner fish in the aquaculture for removal of sea lice from Atlantic salmon (Salmo salar L.). [ABSTRACT FROM AUTHOR]

BackgroundThe Janus kinase/signal transducers and activators of transcription (JAK-STAT) system regulates several biological processes by affecting transcription of genes as a response to cytokines and growth factors. In the present study, we have characterized the STAT genes in lumpfish (Cyclopterus lumpus L.), belonging to the order Perciformes, and investigated regulation of the JAK-STAT signaling pathway upon exposure to bacteria (Vibrio anguillarum) and poly(I:C), the latter mimicking antiviral responses.MethodsCharacterization and evolutionary analyses of the STATs were performed by phylogeny, protein domain, homology similarity and synteny analyses. Antibacterial and antiviral responses were investigated by performing KEGG pathway analysis.ResultsWe observed that lumpfish have stat1a, 2, 3, 4, 5a, 5b, and 6. Transcriptome-wide analyses showed that most components of the JAK-STAT pathway were present in lumpfish. il-6, il-10, il-21, iκBα and stat3 were upregulated 6 hours post exposure (hpe) against bacteria while type I interferons (IFNs), irf1, irf3, irf10, stat1 and 2 were upregulated 24 hpe against poly(I:C).ConclusionsOur findings shed light on the diversity and evolution of the STATs and the data show that the STAT genes are highly conserved among fish, including lumpfish. The transcriptome-wide analyses lay the groundwork for future research into the functional significance of these genes in regulating critical biological processes and make an important basis for development of prophylactic measure such as vaccination, which is highly needed for lumpfish since it is vulnerable for both bacterial and viral diseases.

Lumpfish (Cyclopterus lumpus) is an underutilized marine resource that is currently only being exploited for roe. Lumpfish skin was pre-treated with alkali (0.1M NaOH) and acid (0.1M HCl) at a skin to chemical ratio of 1:10 for 24 h at 5 °C to remove non-collagenous proteins and minerals. The pre-treated skin was washed, and gelatine was extracted with 0.1M of acetic acid at three different ratios (1:5, 1:10, and 1:15), time (12,18, and 24 h), and temperature combinations (12, 28, and 24 °C). The highest total extraction yield (>40%) was obtained with combinations of extraction ratios of 1:15 and 1:10 with a longer time (24 h) and higher temperature (18–24 °C). The highest gelatine content was obtained with an extraction period of 24 h and ratio of 1:10 (>80%). SDS-PAGE analysis confirmed the presence of type-I collagen. A rheological evaluation indicated melting and gelling temperatures, gel strength, and viscosity properties comparable to existing cold-water gelatine sources.

The possibility of replacing the very time and resource demanding salting out (SO) method with isoelectric precipitation (IP) during collagen extraction from common starfish and lumpfish was investigated. The effect of IP on yield, structural and functional properties of the collagens was therefore compared with SO. Application of IP resulted in a higher or similar collagen mass yield compared with SO from starfish and lumpfish, respectively. However, the purity of collagens recovered with IP was lower than those recovered with SO. Replacing SO with IP did not affect polypeptide pattern and tropohelical structural integrity of collagen from the two resources as revealed with SDS-PAGE and FTIR analysis. Thermal stability and fibril formation capacity of collagens recovered with IP were also well preserved. Overall, the results showed that the IP can be a promising resource smart alternative for the classic SO precipitation during collagen extraction from marine resources.

BackgroundBoth bacterial and viral diseases are a major threat to farmed fish. As the antiviral immune mechanisms in lumpfish (Cyclopterus lumpus L.) are poorly understood, lumpfish leukocytes were stimulated with poly(I:C), a synthetic analog of double stranded RNA, which mimic viral infections, and RNA sequencing was performed.MethodsTo address this gap, we stimulated lumpfish leukocytes with poly(I:C) for 6 and 24 hours and did RNA sequencing with three parallels per timepoint. Genome guided mapping was performed to define differentially expressed genes (DEGs).ResultsImmune genes were identified, and transcriptome-wide analyses of early immune responses showed that 376 and 2372 transcripts were significantly differentially expressed 6 and 24 hours post exposure (hpe) to poly(I:C), respectively. The most enriched GO terms when time had been accounted for, were immune system processes (GO:0002376) and immune response (GO:0006955). Analysis of DEGs showed that among the most highly upregulated genes were TLRs and genes belonging to the RIG-I signaling pathway, including LGP2, STING and MX, as well as IRF3 and IL12A. RIG-I was not identified, but in silico analyses showed that genes encoding proteins involved in pathogen recognition, cell signaling, and cytokines of the TLR and RIG-I signaling pathway are mostly conserved in lumpfish when compared to mammals and other teleost species.ConclusionsOur analyses unravel the innate immune pathways playing a major role in antiviral defense in lumpfish. The information gathered can be used in comparative studies and lay the groundwork for future functional analyses of immune and pathogenicity mechanisms. Such knowledge is also necessary for the development of immunoprophylactic measures for lumpfish, which is extensively cultivated for use as cleaner fish in the aquaculture for removal of sea lice from Atlantic salmon (Salmo salar L.).

MFI was extracted from cuttlefish (Sepia officinalis) and used as a colorant, flavoring, and bioactive compound in caviar-like hydrogel beads. The production parameters, including alginate, salt (NaCl), MFI concentration, and pH, were optimized using response surface methodology. The physicochemical properties of beads produced at optimum conditions (NaCl: 2%, alginate: 1.25%, pH: 8.12, and MFI: 1.39%) were compared with commercial lumpfish (Cyclopterus lumpus) caviar. The analyses showed no significant difference between caviar-like beads and commercial lumpfish caviar. These results suggest that caviar-like beads produced under optimum conditions can be commercialized at low cost to provide an opportunity for sustainable aquaculture. [ABSTRACT FROM AUTHOR]

Vibrio anguillarum is the most frequent pathogen affecting fish worldwide. The only known virulent strains of V. anguillarum are serotypes O1, O2, and O3. Genetic differences between the serotypes that could shed insight on the evolution and serotype differences of this marine pathogen are unknown. Here, we fully sequenced and characterized a strain of V. anguillarum O1 (J382) isolated from winter steelhead trout (Oncorhynchus mykiss irideus) in British Columbia, Canada. Koch's postulates using the O1 strain were replicated in naïve lumpfish (Cyclopterus lumpus) and compared to O2. Phenotypic and genotypic comparisons were conducted for serotypes O1, O2, and O3, using biochemical tests and bioinformatic tools, respectively. The genome of V. anguillarum O1 (J382) contains two chromosomes (3.13 Mb and 1.03 Mb) and two typical pJM1-like plasmids (65,573 and 76,959 bp). Furthermore, V. anguillarum O1 (J382) displayed resistance to colistin sulphate, which differs from serotype O2 and could be attributed to the presence of the ugd gene. Comparative genomic analysis, among the serotypes, showed that intra-species evolution is driven by insertion sequences, bacteriophages, and a different repertoire of putative ncRNAs. Genetic heterogeneity in the O-antigen biosynthesis gene cluster is characterized by the absence or the presence of unique genes, which could result in differences in the immune evasion mechanisms employed by the respective serotypes. This study contributes to understanding the genetic differences among V. anguillarum serovars and their evolution. [ABSTRACT FROM AUTHOR]

Various cleaner fish species, such as the lumpfish (Cyclopterus lumpus L.), are used in the sea cage production of Atlantic salmon (Salmo salar L.) as a control measure against the ectoparasitic salmon louse (Lepeophtheirus salmonis). Nonetheless, during severe lice infestation, alternative treatments are required to control parasitic burden. The aim of this study was to gain insight into how lumpfish skin responds to different chemicals used to treat parasites. The authors collected skin from lumpfish from both research facilities (tank‐reared fish) and commercial production (cage‐reared fish) and used operational welfare indicators, in vitro models, histology and transcriptomics to study how the skin responded to two anti‐parasitic oxidative chemicals, hydrogen peroxide (H2O2) and peracetic acid. Lumpfish sampled from the farm were classified as clinically healthy or weak based on their morbidity status, and fish from each category were used to gain insight into how the therapeutics affect the skin barrier. Differences between healthy and weakened (moribund) fish, and between treated fish from each of the two groups, were observed. Histological examination showed an overall reduced skin quality in fish characterized as moribund, including different grades of exposed bony plates. In vitro oxidant‐treated lumpfish skin had reduced the migration capacity of keratocytes, a weakened epidermal barrier, and altered gene transcription, changes that are known predisposing factors to secondary infections. Skin from non‐treated, healthy fish sampled from commercial farms exhibited similar features and attributes to oxidant‐exposed tank‐reared fish from a research facility, suggesting that apparently healthy cage‐held lumpfish exhibited stress responses in the epidermal barrier. The results of the study outline the risks and consequences lumpfish can face if accidentally subjected to potential anti‐parasitic oxidant treatments aimed at Atlantic salmon. It also strengthens the evidence behind the requirement that lumpfish should be removed from the cages before being potentially exposed to this type of treatment and outlines the potential risks of differing husbandry practices upon lumpfish health, welfare and resilience. [ABSTRACT FROM AUTHOR]

Data from research and commercial use of lumpfish were collected from the research facilities of Gifas (Inndyr, Northern Norway, 67.0° N, 14.0° E). The data were sourced from 12 main lumpfish groups subdivided into 66 subgroups (N = 160,729) delivered to Gifas between 2013 and 2020 and used in cleaner-fish research in (a) land-based facilities, (b) small-scale, or (c) large-scale sea pens. The data were standardised and organised into three main headings. Firstly, background information included transfer time, point of origin, mean starting weight and population size on arrival. Other information included to which site the lumpfish were transferred, volume of cage/tank, whether in the presence of salmon or not, stocking density, days at each site and water quality parameters. Causes of mortality were recorded, when possible, for each group, along with calculated mortality rates, patterns, and analytical information, along with imaging where available. Results show that causes of mortality varied within and between research sites. For lumpfish in hatcheries as well as for those deployed at small-scale sea pens, the primary cause of mortality was identified as pathogenic, while for lumpfish deployed at large-scale sea pens, transporting, grading and mechanical delousing were the primary causes of mortality. The results indicate that more research is required to clarify best practices both in commercial hatcheries and salmon cages and further understanding on lumpfish biological requirements and stress physiology is necessary to develop better methods that safeguard lumpfish welfare and meet their needs. [ABSTRACT FROM AUTHOR]

Phaeohyphomycosis caused by Exophiala species represents an important disease of concern for farmed and aquarium-housed fish. The objective of this study was to summarize the clinical findings and diagnosis of Exophiala infections in aquarium-housed Cyclopterus lumpus. Clinical records and postmortem pathology reports were reviewed for 15 individuals from 5 public aquaria in the United States and Canada from 2007 to 2015. Fish most commonly presented with cutaneous ulcers and progressive clinical decline despite topical or systemic antifungal therapy. Antemortem fungal culture of cutaneous lesions resulted in colonial growth for 7/12 samples from 8 individuals. Amplification of the internal transcribed spacer region (ITS) of nuclear rDNA identified Exophiala angulospora or Exophiala aquamarina in four samples from three individuals. Postmortem histopathologic findings were consistent with phaeohyphomycosis, with lesions most commonly found in the integument (11/15), gill (9/15), or kidney (9/15) and evidence of fungal angioinvasion and dissemination. DNA extraction and subsequent ITS sequencing from formalin-fixed paraffin-embedded tissues of seven individuals identified E. angulospora, E. aquamarina, or Cyphellophora sp. in four individuals. Lesion description, distribution, and Exophiala spp. identifications were similar to those reported in farmed C. lumpus. Antemortem clinical and diagnostic findings of phaeohyphomycosis attributable to several species of Exophiala provide insight on the progression of Exophiala infections in lumpfish that may contribute to management of the species in public aquaria and under culture conditions. [ABSTRACT FROM AUTHOR]

Herders are surface-collecting agents that can effectively reduce the surface area of oil slicks during a spill. Currently, two herding agents, Siltech OP-40 (OP-40) and ThickSlick 6535 (TS6535), are approved for use in oil spill response operations by the United States Environmental Protection Agency National Contingency Plan. These products may be deployed when there is evidence that environmental conditions are appropriate for their application and that their use will result in a net environmental benefit. Because the toxicity of these compounds is still poorly understood, toxicity of OP-40 and TS6535 was tested on four commercially relevant North Atlantic marine species: early life stages of green sea urchin (Strongylocentrotus droebachiensis), American lobster (Homarus americanus), Atlantic cod (Gadus morhua) and lumpfish (Cyclopterus lumpus). Lethal and sublethal toxicity data (LC50 and EC50) were determined at different time points. Siltech OP-40 was found to be between 4 and 78 times more toxic than TS6535. Toxicity values ranged from 1.0 (20-min EC50 in sea urchin fertilization) to 13.4 mg/L (3-hr LC50 in lumpfish) for OP-40, and from 7.6 (72-hr LC50 in 24-hour-old embryo cod) to 476.6 mg/L (24-hr EC50 in 20-day-old cod embryo) for TS6536. In terms of decision-making for oil spill response, data from this study supports their operational use, as the measured toxicity values exceeded the theoretical concentrations expected in the environment following the deployment of herding agents., (© The Author(s) 2025. Published by Oxford University Press on behalf of the Society of Environmental Toxicology and Chemistry. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

This document is a corrigendum published in the journal Frontiers in Immunology. It corrects an error in the acknowledgment section of a previously published article titled "Transcriptome-wide analyses of early immune responses in lumpfish leukocytes upon stimulation with poly(I:C)." The correction provides additional information about the funding received for the project and acknowledges the organizations that provided support. The authors apologize for the error and state that it does not affect the scientific conclusions of the article. The corrigendum is open access and was approved by the Frontiers Editorial Office. [Extracted from the article]

Farmed lumpfish (Cyclopterus lumpus) are commonly used as cleaner fish in the salmonid aquaculture industry, but a knowledge gap exists with regards to their body density. Filling this knowledge gap is of importance, as the lumpfish has no swim bladder and thus relies on alternative methods for buoyancy, i.e., the body density difference between the fish and its surroundings. The aims of this study were to measure the body density of lumpfish and investigate the correlation between body density and different operational welfare indicators. A total of 138 lumpfish were sampled at five different aquaculture sites situated in the Faroe Islands. Weight in water and air was measured, body density was calculated, and operational welfare was assessed. The average body density of the juvenile lumpfish was 1.030 g mL−1. Fulton's K, stomach score, and length were negatively correlated to body density, while the hepatosomatic index was positively correlated to body density. Liver colour was correlated to body density, but the groupings were too broad for a final definitive conclusion. The knowledge gained from this study might help the industry improve their understanding of the operational welfare indicators used for lumpfish. Additionally, the knowledge might also help the aquaculture industry improve their husbandry and feeding practices. [ABSTRACT FROM AUTHOR]

Lumpfish are widely used for removing sea lice in salmonid sea-based aquaculture. If these fish are to be harvested and used for human consumption, it is necessary to know how the physical strain associated with removing the lumpfish from the net-cages affects the fish in the short-term, and if live-storage in tanks, well-boats, or nets awaiting slaughter, will result in stress and mortalities. In this study, we investigated the effect of physical stress and mortality in a group of lumpfish recaptured from commercial net-cages, transported to holding tanks, and stored for one week. In addition to cortisol (primary stress response), we analyzed ions directly related to osmoregulation (Na+ and Cl−), osmotic stress (Ca2+), and blood plasma pH as an indicator of a secondary stress response. The aim of the study was to increase the basic physiological understanding of the physiological effects of handling procedures and transport in lumpfish. Only minor, and temporary, effects on primary stress response and secondary stress response were seen in lumpfish recaptured from net-cages and transported to holding facilities, indicating that lumpfish cope well with short transport (here 5 h). These findings are important in a context where lumpfish are harvested for reuse, e.g., human consumption or processing, following their lice-eating stage in net-cages. [ABSTRACT FROM AUTHOR]

In this review, we have systematized current knowledge about the effect of stocking lumpfish (Cyclopterus lumpus) as cleaner fish to control Lepeophtheirus salmonis infestations on farmed Atlantic salmon (Salmo salar L.). The review was prompted by recent reports in which the usefulness of lumpfish has been doubted, and the urgent need to investigate whether common lumpfish can be used to reduce L. salmonis numbers on farmed Atlantic salmon by active grazing on this species. Available published data clearly indicate that lumpfish graze on L. salmonis, and can significantly lower the lice burden in Atlantic salmon farming. It is possible to enhance the lice grazing behavior of lumpfish with the assistance of live feed conditioning prior to sea pen transfer, and with selective breeding. Data indicate that lice grazing of lumpfish is size dependent, and grazing effect is low for lumpfish larger than 200–250 g. Observations from large-scale rearing of Atlantic salmon in open sea cages in Norway, Iceland, the Faroe Islands, and Scotland also indicate that lumpfish can be effective in lowering infestations of L. salmonis on salmon. Overall, this present review reveals that lumpfish can actively contribute to lower numbers of L. salmonis on farmed Atlantic salmon. [ABSTRACT FROM AUTHOR]

Members of the myxovirus resistance (Mx) protein family play an essential role in antiviral immunity. They are Dynamin-like GTPases, induced by interferons. In the current study, we have characterized two predicted MX genes (MX 1 and MX 2) from lumpfish (Cyclopterus lumpus L.), having 12 and 13 exons, respectively. Mx2 has two isoforms (Mx2-X1 and Mx2-X2) which differ in exon 1. The lumpfish Mx proteins contain an N-terminal Dynamin-like GTPase domain, the middle domain (MD) and GTPase effector domain (GED) characteristic for Mx proteins. Phylogenetic analyses grouped all the lumpfish Mx sequences in group 1, and synteny analyses showed that both genes were localized at chromosome 5 in proximity to the genes Tohc7, Atxn7 and Psmd6. In vitro stimulation experiment showed that both MX1 and MX2 -X2 were highly upregulated upon exposure to poly(I:C), but not bacteria, 24 h post exposure, indicating their role in antiviral immunity. • Lumpfish have two functional MX genes. MX 1 and MX 2. • Isoforms exhibit distinct exon patterns, suggesting functional specialization. • In vitro stimulation experiment highlights their crucial role in antiviral immunity. • Establishment of qPCR assays provide an important tool to study antiviral responses in lumpfish in future studies. [ABSTRACT FROM AUTHOR]

Cultivation of lumpfish (Cyclopterus lumpus) as lice cleaner fish for salmon is now expanding. For successful cultivation of a new species, understanding the basic biology of digestive functions is vital to facilitate and optimize diet formulation. This paper presents results from two experiments conducted to deepen our knowledge on lumpfish intestine physiology. Experiment 1 was a 42-day feeding trial in which lumpfish were fed twelve different diets in the following ranges of macronutrients: Protein 43-68%, lipid 4-17%, and carbohydrate 6-17%. Intestinal tissue, gut content and liver were sampled from 6 fish per tank. The results showed that with increasing lipid level and corresponding decrease in protein level, there was a linear decrease in several of the observed biomarkers, including activity of brush border membrane digestive enzymes, expression of genes related to nutrient digestion and transport, ion exchange, immune regulation, and cell remodeling. Increased intracellular accumulation of lipid (steatosis) was observed in gut and liver with increasing dietary lipid level. Fewer effects were observed for increased dietary carbohydrate and corresponding decreased protein level. Experiment 2 was a two-week feeding trial for estimation of macronutrient digestibility in which lumpfish were fed three diets, all containing 55% crude protein, with lipid to carbohydrate ratio of the low lipid diet of 7.5%/18.3%, the medium lipid diet of 13.8%/14.6%, and high lipid diet of 18.1%/9.5%. Fecal samples were collected as pooled samples per tank. These results showed that fatty acid digestibility’s increased as dietary lipid level increased. Of note, starch digestibility decreased greatly as starch level increased, whereas protein digestibility did not change as lipid or starch level varied. Taken together, the present studies indicated that increasing lipid level in the diet with corresponding decrease in protein level affects digestion, absorption, and immune responses in the lumpfish intestine. Variation in dietary carbohydrate to protein level showed less effects, possibly due to low starch digestibility which makes the variation in available carbohydrates much less than the variation in the analysed level of dietary carbohydrates.

Teleosts exhibit extensive diversity of sex determination (SD) systems and mechanisms, providing the opportunity to study the evolution of SD and sex chromosomes. Here we sequenced the genome of the common lumpfish (Cyclopterus lumpus Linnaeus), a species of increasing importance to aquaculture, and identified the SD region and master SD locus using a 70 K single nucleotide polymorphism array and tissue‐specific expression data. The chromosome‐level assembly identified 25 diploid chromosomes with a total size of 572.89 Mb, a scaffold N50 of 23.86 Mb and genome annotation‐predicted 21,480 protein‐coding genes. Genome‐wide association analysis located a highly sex‐associated region on chromosome 13, suggesting that anti‐Müllerian hormone (AMH) is the putative SD factor. Linkage disequilibrium and heterozygosity across chromosome 13 support a proto‐XX/XY system, with an absence of widespread chromosome divergence between sexes. We identified three copies of AMH in the lumpfish primary and alternate haplotype assemblies localized in the SD region. Comparison to sequences from other teleosts suggested a monophyletic relationship and conservation within the Cottioidei. One AMH copy showed similarity to AMH/AMHY in a related species and was also the only copy with expression in testis tissue, suggesting this copy may be the functional copy of AMH in lumpfish. The two other copies arranged in tandem inverted duplication were highly similar, suggesting a recent duplication event. This study provides a resource for the study of early sex chromosome evolution and novel genomic resources that benefits lumpfish conservation management and aquaculture. [ABSTRACT FROM AUTHOR]

Lumpfish are utilized to combat ectoparasitic epidemics in salmon farming. Research gaps on both cleaning behavior and client preferences in a natural environment, emphasizes the need to investigate the physiological impacts on lumpfish during cohabitation with piscivorous Atlantic salmon. Lumpfish (39.9 g, S.D ± 8.98) were arranged in duplicate tanks (n = 40 per treatment) and exposed to Live Atlantic salmon (245.7 g, S.D ± 25.05), salmon Olfaction or lifelike salmon Models for 6 weeks. Growth and health scores were measured every second week. In addition, the final sampling included measurements of neuromodulators, body color, and plasma cortisol. A stimulation and suppression test of the hypothalamic-pituitary-interrenal (HPI) axis was used for chronic stress assessment. Results showed that growth, health scores, and body color remained unaffected by treatments. Significant reductions in levels of brain dopamine and norepinephrine were observed in Live compared to Control. Plasma cortisol was low in all treatments, while the stimulation and suppression test of the HPI axis revealed no indications of chronic stress. This study presents novel findings on the impact on neuromodulators from Atlantic salmon interaction in the lumpfish brain. We argue that the downregulation of dopamine and norepinephrine indicate plastic adjustments to cohabitation with no negative effect on the species. This is in accordance with no observed deviations in welfare measurements, including growth, health scores, body color, and stress. We conclude that exposure to salmon or salmon cues did not impact the welfare of the species in our laboratory setup, and that neuromodulators are affected by heterospecific interaction. [ABSTRACT FROM AUTHOR]

Lumpfish are utilized to combat ectoparasitic epidemics in salmon farming. Research gaps on both cleaning behavior and client preferences in a natural environment, emphasizes the need to investigate the physiological impacts on lumpfish during cohabitation with piscivorous Atlantic salmon. Lumpfish (39.9 g, S.D ± 8.98) were arranged in duplicate tanks (n = 40 per treatment) and exposed to Live Atlantic salmon (245.7 g, S.D ± 25.05), salmon Olfaction or lifelike salmon Models for 6 weeks. Growth and health scores were measured every second week. In addition, the final sampling included measurements of neuromodulators, body color, and plasma cortisol. A stimulation and suppression test of the hypothalamic-pituitary-interrenal (HPI) axis was used for chronic stress assessment. Results showed that growth, health scores, and body color remained unaffected by treatments. Significant reductions in levels of brain dopamine and norepinephrine were observed in Live compared to Control. Plasma cortisol was low in all treatments, while the stimulation and suppression test of the HPI axis revealed no indications of chronic stress. This study presents novel findings on the impact on neuromodulators from Atlantic salmon interaction in the lumpfish brain. We argue that the downregulation of dopamine and norepinephrine indicate plastic adjustments to cohabitation with no negative effect on the species. This is in accordance with no observed deviations in welfare measurements, including growth, health scores, body color, and stress. We conclude that exposure to salmon or salmon cues did not impact the welfare of the species in our laboratory setup, and that neuromodulators are affected by heterospecific interaction.

Vibrio anguillarum is the most frequent pathogen affecting fish worldwide. The only known virulent strains of V. anguillarum are serotypes O1, O2, and O3. Genetic differences between the serotypes that could shed insight on the evolution and serotype differences of this marine pathogen are unknown. Here, we fully sequenced and characterized a strain of V. anguillarum O1 (J382) isolated from winter steelhead trout (Oncorhynchus mykiss irideus) in British Columbia, Canada. Koch’s postulates using the O1 strain were replicated in naïve lumpfish (Cyclopterus lumpus) and compared to O2. Phenotypic and genotypic comparisons were conducted for serotypes O1, O2, and O3, using biochemical tests and bioinformatic tools, respectively. The genome of V. anguillarum O1 (J382) contains two chromosomes (3.13 Mb and 1.03 Mb) and two typical pJM1-like plasmids (65,573 and 76,959 bp). Furthermore, V. anguillarum O1 (J382) displayed resistance to colistin sulphate, which differs from serotype O2 and could be attributed to the presence of the ugd gene. Comparative genomic analysis, among the serotypes, showed that intra-species evolution is driven by insertion sequences, bacteriophages, and a different repertoire of putative ncRNAs. Genetic heterogeneity in the O-antigen biosynthesis gene cluster is characterized by the absence or the presence of unique genes, which could result in differences in the immune evasion mechanisms employed by the respective serotypes. This study contributes to understanding the genetic differences among V. anguillarum serovars and their evolution.

Renibacterium salmoninarum is a Gram-positive, intracellular pathogen that causes Bacterial Kidney Disease (BKD) in several fish species in freshwater and seawater. Lumpfish (Cyclopterus lumpus) is utilized as a cleaner fish to biocontrol sea lice infestation in Atlantic salmon (Salmo salar) farms. Atlantic salmon is susceptible to R. salmoninarum, and it can transfer the infection to other fish species. Although BKD outbreaks have not been reported in lumpfish, its susceptibility and immune response to R. salmoninarum is unknown. In this study, we evaluated the susceptibility and immune response of lumpfish to R. salmoninarum infection. Groups of lumpfish were intraperitoneally (i.p.) injected with either R. salmoninarum (1×107, 1×108, or 1×109 cells dose-1) or PBS (control). R. salmoninarum infection kinetics and mortality were followed for 98 days post-infection (dpi). Transcript expression levels of 33 immune-relevant genes were measured in head kidney (n = 6) of fish infected with 1×109 cells/dose and compared to the control at 28 and 98 dpi. Infected lumpfish displayed characteristic clinical signs of BKD. Lumpfish infected with high, medium, and low doses had a survival rate of 65%, 93%, and 95%, respectively. Mortality in the high-dose infected group stabilized after 50 dpi, but R. salmoninarum persisted in the fish tissues until 98 dpi. Cytokines (il1β, il8a, il8b), pattern recognition receptors (tlr5a), interferon-induced effectors (rsad2, mxa, mxb, mxc), and iron regulation (hamp) and acute phase reactant (saa5) related genes were up-regulated at 28 dpi. In contrast, cell-mediated adaptive immunity-related genes (cd4a, cd4b, ly6g6f, cd8a, cd74) were down-regulated at 28 dpi, revealing the immune suppressive nature of R. salmoninarum. However, significant upregulation of cd74 at 98 dpi suggests induction of cell-mediated immune response. This study showed that R. salmoninarum infected lumpfish in a similar fashion to salmonid fish species and caused a chronic infection, enhancing cell-mediated adaptive immune response.