Thermoregulation in ectothermic animals is influenced by the ability to effectively respond to thermal variations. While it is known that ectotherms are affected by thermal changes, it remains unknown whether physiological and/or metabolic traits are impacted by modifications to the thermal environment. Our research provides key evidence that fish ectotherms are highly influenced by thermal variability during development, which leads to important modifications at several metabolic levels (e.g., growth trajectories, microstructural alterations, muscle injuries, and molecular mechanisms). In Atlantic salmon (Salmo salar), a wide thermal range (Δ_T 6.4°C) during development (posthatch larvae to juveniles) was associated with increases in key thermal performance measures for survival and growth trajectory. Other metabolic traits were also significantly influenced, such as size, muscle cellularity, and molecular growth regulators possibly affected by adaptive processes. In contrast, a restricted thermal range (Δ_T 1.4°C) was detrimental to growth, survival, and cellular microstructure as muscle growth could not keep pace with increased metabolic demands. These findings provide a possible basic explanation for the effects of thermal environment during growth. In conclusion, our results highlight the key role of thermal range amplitude on survival and on interactions with major metabolism‐regulating processes that have positive adaptive effects for organisms.

A fever, or increased body temperature, is a symptom of inflammation, which is a complex defence reaction of the organism to pathogenic infections. After pathogens enter the body, immune cells secrete a number of agents, the functions of which stimulate the body to develop a functional immune and fever response. In mammals it is known that PGE2 is the principal mediator of fever. The extent to which PGE2 and other pro-inflammatory cytokines such as TNF-α, IL-6, or IL-1β could be involved in the induction of behavioural fever in fish remains to be clarified. Several members of the transient receptor potential (TRP) family of ion channels have been implicated as transducers of thermal stimuli, including TRPV1 and TRPV2, which are activated by heat. Here we show that members of the TRP family, TRPV1 and TRPV4, may participate in the coordination of temperature sensing during the behavioural fever. To examine the behavioral fever mechanism in Salmo salar an infection with IPNV, infectious pancreatic necrosis virus, was carried out by an immersion challenge with 10 × 105 PFU/mL-1 of IPNV. Behavioural fever impacted upon the expression levels of both TRPV1 and TRPV4 mRNAs after the viral challenge and revealed a juxtaposed regulation of TRPV channels. Our results suggest that an increase in the mRNA abundance of TRPV1 is tightly correlated with a significant elevation in the expression of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α and PGE2) in the Pre-Optic Area (POA) and cytokine release in plasma. Together, these data indicate that the reduction of TRPV4 expression during behavioural fever may contribute to the onset of behavioural fever influencing movement toward higher water temperatures. Our data also suggest an effect of TRPV channels in the regulation of behavioural fever through activation of EP3 receptors in the central nervous system by PGE2 induced by plasma-borne cytokines. These results highlight for first time in mobile ectotherms the key role of pro-inflammatory cytokines and TRPV channels in behavioural fever that likely involves a complex integration of prostaglandin induction, cytokine recognition and temperature sensing.

Although the relationship between the use of antimicrobials and the development of resistant bacteria is well established, information about the use of antimicrobials in companion animals has been poorly described, which represents a risk to public health. The aim of this study was to describe the antimicrobial prescription patterns of Chilean companion animal veterinarians. A nationally distributed survey targeted at companion animal veterinarians was designed. The survey included questions about the veterinarian’s demographics, bacterial diseases treated, prescribed antimicrobials, and the use of laboratory diagnostic tools. Three hundred twenty-three responses were collected, most of the respondents were female (59.4%). The most frequently reported bacterial diseases were pyoderma (17.2%), followed by otitis and abscesses (7.4%). The antimicrobials most used corresponded with critically or highly important drugs for veterinary and human use, including β-lactams (65.3%), quinolones (36.2%) and tetracyclines (23.2%). Only 15% of the veterinarians reported the use of laboratory diagnostic tests, although 67% declared they were aware of the official antimicrobial classification schemes. Our results describe for the first time the usage of antimicrobials by veterinarian practitioners in Chile to treat different diseases in companion animals. The data presented here provide a baseline that could help to promote the implementation of clinical guidelines and regulations in order to improve current treatments.

Sea lice are a group of ectoparasite copepods negatively affecting fish health in the salmon farming industry worldwide. Due to their biology, including several stages of development with different sensitivities to chemotherapeutants and their complex host–parasite interactions, the control of sea lice represents one of the major obstacles for sustainable aquaculture. Interdisciplinary approaches are required to avoid the environmental impacts of antiparasites commercially used during the fish production cycle and the increasing emergence of drug resistance in lice populations. Herein, control methods based on genomic analyses will allow for the development of novel tools such as vaccines, immune‐modulators, in‐feed masking compounds and non‐pharmacological therapies. This review highlights the genomic knowledge on the race between hosts and sea lice, with emphasis on Salmo salar and Oncorhynchus kisutch as host fish species and Caligus rogercresseyi as the main threat affecting the Chilean salmon industry.