Percorrer por autor "Guerreiro, Pedro Miguel"
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- Acute resilience, chronic costs: metabolic responses to warming and hypoxia in the sedentary lusitanian toadfish, halobatrachus didactylusPublication . Molina, Juan M.; Kunzmann, Andreas; Costa, Rita; Modesto, Teresa; Carvalho Alves, Alexandra; Guerreiro, Pedro MiguelCoastal fishes can adapt to water warming and hypoxia; however, acute tolerance does not necessarily predict longer-term performance and survival. This may be especially important in sedentary, site-faithful species with limited escape to escape increasingly unfavorable habitats. We assessed the climate-related stress responses of the Lusitanian toadfish, Halobatrachus didactylus, a benthic estuarine fish from the Northeast Atlantic, to water warming and hypoxia. Objectives: We aimed to determine the aerobic energy budget, thermal limits (CTmax), and critical oxygen tension (Pcrit), as well as blood indicators of metabolism, altered physiology and systemic stress, as proxies for whole-organism homeostatic state, thereby informing future ecophysiological assessments and bioindicator development in a context of environmental change. Methodology: We determined standard, routine, and maximum metabolic rates; aerobic scope; and critical thermal maximum (CTmax) and critical oxygen (Pcrit) thresholds on a set of 134 individuals ranging from 12 to 160 g in weight. On a different set of individuals (n = 48; 76.3 ± 2.6 g; 16.1 ± 0.18 cm), we simulated 30 days of seasonal scenarios combining low and high temperature with normoxia or hypoxia, followed by integrated metabolic, hematological, biochemical, and multivariate analyses. Results: Acute trials showed high short-term resilience: H. didactylus had an exceptionally low standard metabolic rate and routine metabolic rate, high CTmax (34.82 ± 0.66 °C), and strong hypoxia tolerance (Pcrit 0.59–1.97 mg O2 L−1), although smaller individuals were more sensitive. After 30 days, however, warming more than doubled standard and routine metabolic rates, while warm hypoxia reduced metabolic output relative to warm normoxia, consistent with metabolic depression under compounded stressors. This treatment also showed shifts in glucose, liver mass, red blood cell count, and hematocrit, identifying warm, oxygen-poor water as the most physiologically costly scenario for this species. Conclusions: Together, these results show that high acute tolerance does not guarantee resilience to climate change. In sedentary fishes, survival may depend less on surviving extremes than on maintaining energetic balance, oxygen transport capacity, and physiological homeostasis in increasingly warm, oxygen-poor coastal habitats.
- Aglomerular renal function in teleosts: A comparative molecular and physiological approachPublication . Pinto Teixeira, José Pedro; Pinto, Bernardo; Wilson, Jonathan M.; Guerreiro, Pedro Miguel; Castro, FilipeThe aglomerular kidney, characterised by the absence of functional glomeruli and reliance on tubular secretion alone, has evolved independently across multiple teleost lineages occupying diverse environments, including notothenioids of the Southern Ocean, gadids of cold North Atlantic and Arctic waters, and syngnathids distributed across temperate and tropical seas. Despite sharing this independently derived renal architecture, these groups face markedly distinct osmotic, thermal and chemical challenges in their natural habitats. How aglomerular kidneys cope with environmental stressors, including fluctuations in temperature and salinity, and how they handle the excretion of xenobiotics and other exogenous compounds through exclusively tubular mechanisms, remains poorly understood. The physiological and molecular responses underlying renal function in these lineages have received comparatively little attention relative to their glomerular counterparts. Objective: This study investigates how aglomerular kidneys across phylogenetically distinct teleost lineages respond, at molecular and physiological levels, to contrasting environmental conditions, namely temperature and salinity challenges predicted to alter the functional demands on renal osmoregulation. Methodology: Adult and juvenile specimens from target lineages were subjected to controlled exposure experiments combining different temperature and salinity regimes. Blood and urine samples were collected to assess osmolality and ionic composition. Renal tissues were processed for gene expression analysis of key transport and structural genes, histology, immunohistochemistry and enzymatic activity assays, providing an integrated picture of renal function under each condition. Results: Molecular analyses are currently underway. Preliminary work has established protocols for RNA extraction and quantitative PCR across target species, enabling comparative gene expression profiling to proceed across the full dataset. Conclusions: A comparative physiological and molecular approach across aglomerular teleost lineages will clarify whether shared renal architecture translates into shared functional responses to environmental challenge and identify lineage-specific mechanisms of renal adaptation, with broader relevance for predicting how these fishes may respond to ongoing environmental change.
- Are there differential roles in the parental behaviour of the chameleon cichlid australoheros facetus?Publication . Oliveira, Gonçalo; Saraiva, João; Jesus, Nuno F.; Guerreiro, Pedro MiguelCichlids are social fishes well known for their complex behaviour. The chameleon cichlid, Autraloheros facetus, is native to South American river drainages and is currently established in several Mediterranean-type drainages in southern Portugal as an invasive species. Their high local recruitment, territorially, and parental care activities are possible advantages in competing with native fish and achieving high reproductive success. The main objective of this work was to characterise the behaviours of the males and females of the species A. facetus upon pair formation and their roles during parental behaviour at different stages of offspring development for the purpose of gathering important basic knowledge on fish biology to apply in the control of the species’ populations. To attain this initial goal, we used observation techniques and video recording protocols to characterise the specific activities performed by each individual during reproductive and parental stages (pair formation, eggs, attached larvae, and free-swimming larvae), identifying the main tasks, and assessing the time spent on each task by each member of the reproductive pair. The breeding pairs were obtained as a result of the social hierarchy formed in each social group: groups of six individuals of similar size were placed in individual tanks fitted with a bottom biological filter, in which the temperature was increased to 24 ◦C at an expanded photoperiod. Social behaviours were recorded and characterised, expanded on a previously established ethogram. The results obtained so far allow us to establish a set of aggressive behaviours towards other fish (striking, chasing, biting), nest preparing behaviours (digging, cleaning), caring (caring, fetching), and guarding behaviours towards the offspring (hovering, patrolling). Concerning the rate of occurrence of social behaviours in randomised 5 min periods (frequency of specific behaviours per each 5 min period) show that in the pair formation stage, males present a more aggressive nature with frequent occurrence of striking (rstriking = 1) and biting (rbiting = 0.31). On the other hand, at the egg stage, the rate of occurrence of parental behaviours shows the dominance of females to prepare the nest (rdigging = 0.91) and caring for the eggs (rcaring = 3.64), while males are more vigilant (rparental hovering = 0.95). At the attached larvae stage, this tendency continues with higher occurrence rates: males focus on vigilance (rparental hovering = 1.6) and patrolling (rpatrolling = 2), and females care for the recently hatched larvae (rfetching = 4). Finally, at the free-swimming larvae stage, there is a turn and a small decrease in the occurrence of these activities: males oversee nest maintenance (rdigging = 1.09), and females patrol the tank (rpatrolling = 0.71) and care for the larvae (rfetching = 2.02). These preliminary data suggest differential roles for male and female A. facetus, that evolve during parental behaviour, for which further experimental paradigms will be designed to explore underlying proximate causes.
- Assessing fish welfare in small-scale commercial fixed-net fisheries off the southern portuguese coastPublication . Samel, Vighnesh Nilesh; Costa, Rita; Marçalo, Ana; Frade, Magda; Bentes, Luis; Saraiva, João; Gonçalves, Jorge Manuel Santos; Guerreiro, Pedro Miguel; Claudio D'IglioDespite a growing interest in animal welfare in production systems, research on fish welfare remains limited, particularly in commercial fisheries. Fish caught in fixed-net fisheries experience multiple stressors from the time of capture to mortality on deck considered detrimental to their welfare. We examined the impact of bottom-set gill nets and on-board handling on catch welfare using behavioural and physiological indicators. Vitality assessments were performed on four commercially important fish species on-board fishing vessels through a devised vitality scale that included behaviours, morphological condition and reflexes as indicators of welfare. Physiological stress parameters (Cortisol, Glucose, Lactate and Osmolality) were evaluated in blood collected on deck and analysed in relation to the vitality scores. The vitality at arrival on deck as well as the rate of decrease in vitality differed significantly amongst the tested species. Furthermore, Generalised Linear Models predicted that several biological, operational, and environmental variables significantly affect the extent of time the fish shows activity, and hence, on the welfare. Elevated average cortisol levels were found at all the vitality stages highlighting the stress experienced by fish due to the fishing process. The findings of this study enable us to recommend welfare-friendly methods in set-net fisheries to promote better fishing standards.
- Assessment of the reproductive status of captive populations of endangered leuciscid species from the iberian peninsula: a. hispanica, I. lusitanicum and a. occidentalePublication . Hernandez, Ana; Gil, Fátima; Sousa-Santos, Carla; Cabrita, Elsa; Guerreiro, Pedro Miguel; Gallego, VictorPopulations of freshwater fish species endemic to the Iberian Peninsula have been declining since the mid-20th century, and the captive breeding of highly endangered species is considered to be a useful tool to restock declining populations. A pioneer project of supportive breeding of critically endangered fish started in 2007 at the Aquário Vasco da Gama (AVG), and this work aims to show the reproductive status of the breeders which make up the current captive broodstoks. Populations of different endangered leuciscid species (Anaecypris hispanica, Iberochondrostoma lusitanicum and Achondrostoma occidentale) were sampled at AVG during the spring of 2022. Breeders were counted and sexed, and males were stripped to check for the presence of spermatozoa. The sperm volume was assessed visually, and spermatozoa motility was assessed by a CASA system. Sperm samples were classified into four classes based on the percentage of motile cells: C-I ≤ 25%, C-II = 25–50%, C-III = 50–75%; and C-IV > 75%. The captive population of A. hispanica consisted of 63 individuals and showed a 40% of spermiating males, with an average volume of 5–10 µL. The histogram of sperm quality reported that 15% males had sperm motility of C-II, 50% of males had sperm motility of C-III and, finally, 35% of males had sperm with the high-quality class (C-IV). The population of I. lusitanicum consisted of 599 individuals and showed 93% of spermiating males, with an average volume of 15–20 µL. The histogram of sperm quality reported that most part of the males had good sperm quality belonging to C-III and C-IV class (26% and 71%, respectively), while just 1 male showed bad quality sperm (C-II). The captive population of A. occidentale consisted of 193 individuals, showing a 62% of spermiating males with an average volume of 20–25 µL. The histogram showed that 6% males had sperm motility of C-I, 26% of males had sperm motility of C-II, the most part of the males (45%) showed a sperm quality of C-III and, finally, 23% of males had sperm with the high-quality class (C-IV). Since the project began in 2007, more than 12,000 fish of these three critically endangered species have been released to restock the populations from which the respective wild breeders were caught. All captive fish were released after a maximum of three consecutive generations in captivity, and new stocks were established with wild adults from the target populations, to avoid the negative effects of inbreeding and genetic drift on the original genetic pool.
- Combined effects of PVC microplastics and thermal rise alter the oxidative stress response in Antarctic fish Harpagifer antarcticus and Sub-Antarctic Harpagifer bispinisPublication . Nualart, Daniela P.; Paschke, Kurt; Guerreiro, Pedro Miguel; McCormick, Stephen D.; González-Wevar, Claudio; Cheng, Chi-Hing Christina; Chacoff, Luis VargasThis study evaluated the oxidative stress response in two cold-water fish species, the Antarctic Harpagifer antarcticus and the sub-Antarctic H. bispinis, following exposure to single and combined stressors: polyvinyl chloride (PVC) microplastics and thermal increase. Fish were exposed for 24 h to two temperature regimes (2 degrees C and 5 degrees C for H. antarcticus; 8 degrees C and 12 degrees C for H. bispinis) and were orally administered a PVC microplastic solution (200 mg/L). Oxidative stress was assessed through transcriptional and enzymatic activity analyses of key antioxidant markers: catalase, glutathione peroxidase, superoxide dismutase, and glutathione reductase. In H. antarcticus, gill antioxidant gene expression decreased in response to both stressors when applied individually, while H. bispinis exhibited transcriptional upregulation under the same conditions. In H. antarcticus, enzymatic activity in gill tissues increased for all four enzymes following exposure to both microplastics and elevated temperature. In contrast, H. bispinis showed a differential enzymatic response: thermal stress induced CAT activity, whereas exposure to microplastics specifically increased GR activity. At the hepatic level, H. antarcticus displayed increased transcription of antioxidant genes following exposure to both stressors. In H. bispinis, transcriptional upregulation was limited to GR and SOD in response to microplastics. However, under the combined exposure of multiple stressors, an inactivation of the antioxidant enzyme response was observed in the gills. This could indicate a functional collapse of the antioxidant system under conditions of exacerbated acute stress. The observed responses raise concerns about the potential vulnerability of polar and subpolar fishes, considering their ecological importance in trophic networks and the increasing pressure from multiple anthropogenic stressors in a rapidly changing climate.
- A comparison of olfactory sensitivity in seawater- and freshwater-adapted bass, dicentrarchus iabraxPublication . Velez, Zélia; Hubbard, Peter; Guerreiro, Pedro MiguelFish rely heavily on olfaction for many aspects of their lives including foraging, defense, migration, and reproduction. Olfactory receptor neurons in the olfactory epithelium are in direct contact with the water, and are, therefore, exposed to changes in water chemistry. The European seabass, Dicentrarchus labrax, uses estuaries as feeding grounds and migrates between seawater and brackish water; but some can be found in 100% freshwater. However, little is known about how the olfactory system adjusts to waters of such different ionic composition and whether this affects its function and ability to discriminate between odorants. The aim of this study was, therefore, to compare olfactory sensitivity in seabass adapted to either seawater (SW) or freshwater (5 ppt; FW), to odorants conveyed at different salinities, using multi-unit recording from the olfactory nerve. In SW-adapted fish, olfactory sensitivity to amino acids (AA) was consistently higher when AA were presented in seawater (SW-AA) than when presented in freshwater (FW-AA), whereas in FW-adapted fish, olfactory sensitivity to FW-AA was either equal or slightly lower to SW-AA. SW-adapted fish responded to decreases in external [Ca2+] and to increases in external [Na+ ]. FWadapted fish responded to increases of both ions. In SW-adapted fish, Ca2+-free artificial seawater (ASW) completely inhibited olfactory responses to amino acids, whereas Na+ -free ASW had no effect. However, in FW-adapted fish, lack of either ion in the water had no effect. Taken together, these results suggest that, as a primarily marine species, the olfactory system of the seabass is more sensitive in seawater; however, it can still function in freshwater, albeit with reduced sensitivity. Furthermore, in seawater, the olfactory transduction process is likely mediated by influx of external Ca2+, but not Na+ . In FW-adapted fish, the transduction process relies on neither external Ca2+ nor Na+ , suggesting that the process of hyperosmoregulatory ability to adjust to life in ion-poor water. Further work is needed to clarify how changes in salinity affect olfactory sensitivity, and the mechanisms by which euryhaline species are able to adapt to such changes when moving between media of different ionic composition and variable pH.
- Evaluating repetitive mucus extraction effects on mucus biomarkers, mucus cells and skin-barrier status in a marine fish modelPublication . Sanahuja, Ignasi; Guerreiro, Pedro Miguel; Girons, Albert; Fernández-Alacid, Laura; Ibarz, AntoniAmong all the mucosal barriers, the skin and its surrounding mucus are possibly the main defensive tools used by fish against the environment. Due to its less-invasive extraction, the study of its production and functions has gained high interest in the last years. However, there are still many gaps in research, such as the possible alteration of mucus composition or the skin integrity resulting from the sampling process. In the current study, skin mucus extraction impacts were determined by comparing the effects of one-single extraction (SEG; single extraction group) and three successive extractions (REG; repetitive extractions group, separated by 4 days) on mucus properties and on skin epithelial integrity. In terms of analytical evaluation, plasma biomarkers and plasma antibacterial capacity were also determined. With regard skin histology and skin barrier properties, both SEG and REG did not evidence differences with respect to intact skin (ØEG). Interestingly, the repetitive mucus extraction protocol seemed to activate skin mucus turnover, significantly increasing the number of low-size mucus cells (cell area < 100 µm2 ) and reducing the number of high-size mucus cells (cell area > 150 µm2 ). Repetitive extraction of skin mucus diminished the amounts of soluble protein and glucose in mucus with regard to one-single extraction and increased cortisol exudation. These metabolites remained unaltered in plasma, indicating the different response among both sampling targets. Despite mucus biomarkers modification, the antibacterial capacity against the pathogenic bacterial (P. anguilliseptica and V. anguillarum) was maintained in both plasma and mucus irrespective of the number of mucus extractions. Overall, the mucus sampling protocol scarcely affected skin integrity and mucus antibacterial properties and only modified metabolites exudation, evidencing a feasible and minimally invasive method for studying fish health and welfare as an alternative or as a complement to plasma. The knolwdege provided here highlighted that this methodology is putatively transferable to farm culture conditions and showed that it is very useful for the study of threatened species aimed at preserving fish welfare.
- Evaluation of an acute osmotic stress in European Sea bass via skin mucus biomarkersPublication . Ordóñez-Grande, Borja; Guerreiro, Pedro Miguel; Sanahuja, Ignasi; Fernández-Alacid, Laura; Ibarz, AntoniEuropean sea bass is a marine teleost which can inhabit a broad range of environmental salinities. So far, no research has studied the physiological response of this fish to salinity challenges using modifications in skin mucus as a potential biological matrix. Here, we used a skin mucus sampling technique to evaluate the response of sea bass to several acute osmotic challenges (for 3 h) from seawater (35%_) to two hypoosmotic environments, diluted brackish water (3%_) and estuarine waters (12%_), and to one hyperosmotic condition (50%_). For this, we recorded the volume of mucus exuded and compared the main stress-related biomarkers and osmosis-related parameters in skin mucus and plasma. Sea bass exuded the greatest volume of skin mucus with the highest total contents of cortisol, glucose, and protein under hyper salinity. This indicates an exacerbated acute stress response with possible energy losses if the condition is sustained over time. Under hypo salinity, the response depended on the magnitude of the osmotic change: shifting to 3%_ was an extreme salinity change, which affected fish aerobic metabolism by acutely modifying lactate exudation. All these data enhance the current scarce knowledge of skin mucus as a target through which to study environmental changes and fish status.
- Heat hardening in grey mullets: physiological responses of juvenile chelon labrosus and chelon aurata under simulated short-term marine heatwavesPublication . Amaral, Inês; Costa, Rita; Zamora-López, Antonio; Zimmermann, Wim; Guerrero-Gómez, Adrián; Gregorio, Silvia; Guerreiro, Pedro MiguelIntroduction: Marine heatwaves are increasing in frequency and intensity, posing major challenges for fishes inhabiting shallow coastal ecosystems. Short-term exposure to extreme warming can alter metabolic performance and thermal tolerance, with potential consequences for species persistence and school composition in thermally variable habitats. Understanding the capacity of coastal fishes to withstand acute warming events is therefore essential for predicting ecological responses to climate change. Objective: We aimed to determine the effects of simulated marine heatwaves on thermal tolerance and metabolic performance in juvenile grey mullets, Chelon labrosus and Chelon aurata, two abundant sympatric species inhabiting the Ria Formosa lagoon (southern Portugal). Methodology: Juvenile mullets acclimated at 17 °C were exposed to simulated heatwave treatments of 23, 27, or 33 °C and sampled either at peak temperature or after 48 h and 1-week recovery at 17 °C. Critical thermal maximum (CTmax, using a 1 °C/min thermal ramp), static oxygen consumption (MO2), and intermittent respirometry parameters were measured. Standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS) were derived from intermittent respirometry. A complementary temperature-ramp (>3 h at each temperature step 17, 23, 27 and 33 °C) was performed to evaluate routine metabolic rate and estimate Q10 values across increasing temperatures. Additional plasma and tissue analyses are being conducted to assess energetic substrate mobilization and cellular responses to thermal and oxidative stress. Results: CTmax increased significantly with warming in both treatment modes, demonstrating rapid heat hardening in juvenile mullets. Fish exposed to 27 and 33 °C exhibited higher CTmax than control fish, and this elevated tolerance persisted after recovery. Chelon labrosus showed slightly higher CTmax values than C. aurata. Oxygen consumption increased with temperature, with the strongest responses occurring at 33 °C. SMR increased markedly with warming, particularly in heatwave-exposed fish, while MMR increased mainly at the highest temperature treatment. In contrast, AS showed no clear thermal optimum or decline across treatments. Routine metabolic rate increased non-linearly with temperature in the complementary ramp experiment, with a mean Q10 of 2.28, confirming strong thermal dependence of metabolism. Conclusions: Juvenile mullets possess substantial short-term thermal plasticity and can rapidly increase heat tolerance during marine heatwaves but this enhanced tolerance is accompanied by elevated metabolic costs under extreme warming, indicating potential energetic trade-offs near upper thermal limits. Differential physiological responses between species may influence school composition and ecological performance across thermal landscapes. Ongoing plasma and tissue analyses will further clarify the energetic and cellular mechanisms underlying thermal and oxidative stress resilience in coastal fishes.