Gilson Luiz Volpato

São Paulo State University | Unesp · Department of Physiology

Information on fish preference for environmental conditions can be a useful tool to offer them what they want, an important requirement for welfare purposes. Giving that such an approach deals with psychological states of the fish, we investigated whether psychological stress affects fish preference. In this study, we found that the aversive condit...

Preference tests have been applied to detect better welfare conditions for the animals. Among these tests, the available choice options are variable and thus, the best preferences may not be included. Considering welfare purposes, it is relevant to know whether the animal would select a second option as a preference in this situation, which could b...

The identification of animal preferences is assumed to provide better rearing environments for the animals in question. Preference tests focus on the frequency of approaches or the time an animal spends in proximity to each item of the investigated resource during a multiple-choice trial. Recently, a preference index (PI) was proposed to differenti...

Criteria for scientific authorship still lack of universal consensus among scientists, thus rising speculations that, sometimes, only justify the unjustifiable. In this text, my focus is the empirical science and I propose that participation in data collection (DC) or provision of material resources (MR) for the research are neither sufficient, nor...

Giving animals their preferred items (e.g., environmental enrichment) has been suggested as a method to improve animal welfare, thus raising the question of how to determine what animals want. Most studies have employed choice tests for detecting animal preferences. However, whether choice tests represent animal preferences remains a matter of cont...

Every finding released by a scientific publication is expected to provide an area of study with new solutions and insights. In this task, the role of the scientist is of the utmost importance, as science is a vehicle through which humans interpret the world, and the scientific knowledge is a construct based on convincing empirical evidence. Scienti...

Os ácidos biliares são potentes estimulantes olfatórios e gustatórios em peixes. Registros em eletro-olfactograma foram usados para testar se o epitélio olfatório de Pseudoplatystoma corruscans, pintado, é sensível aos ácidos biliares, alguns dos quais têm sido propostos como feromônios. Foram selecionados cinco de uma lista de trinta ácidos biliar...

Here I argue that theoretical foundations of science and communication should guide scientific writing. Every decision comes from this basic knowledge, which supports what I call the logical method for scientific writing. After an evaluation of some aspects of the publication scenario, I indicate some of the main logical and communication requireme...

We investigated chemical cues among groups of zebrafish (Danio rerio) when communicating information about the risk of predation. We found that visual cues of the predator (tiger Oscar, Astronotus ocellatus) did not increase whole-body cortisol levels in groups of zebrafish but that water conditioned by these (donor) zebrafish stressed (target) con...

Living animals exploit information released from dead animals to conduct adaptive biological responses. For instance, a recently published study has shown that avoidance behavior is triggered by death-associated odors in zebrafish. Stress can clearly act as an adaptive response that allows an organism to deal with an imminent threat. However, it ha...

We demonstrate the efficacy of propofol (2,6-diisopropylphenol) as an anesthetic when administered to fish in an immersion bath and show the absence of genetic side effects following short-term exposure to the drug. All tested fish were anesthetized (as indicated by loss of posture and lack of response to physical stimulation), and both the comet a...

Mate selection and mating success in the Amazonian angelfish, Pterophyllum scalare were experimentally investigated in the laboratory. This species has a breeding system where male body size and substrate type could be decisive for mate selection by females. The aims of this study were to identify the male traits contributing to reproductive succes...

The hybrid red tilapia, Oreochromis niloticus x O. mossambicus, is utilized in semiintensive fish culture practices in Northeastrn Brazil, and this paper reports on the reproductive behaviour and gonadal development of this hybrid. Mature males and females of hybrid red tilapia were observed under laboratory conditions during their reproductive pha...

Here, I emphasize the need for collaborative research among scientists. Such collaboration should aim to address the genuine integrative need to build knowledge rather than searching for visibility based on the international prestige of a collaborator, increased productivity, or funding. Scientists must provide a valid and honest counterpart, such...

Nile tilapia fish were individually reared under similar light levels for 8 weeks under five colored light spectra (maximum wavelength absorbance): white (full light spectrum), blue (∼452 nm), green (∼516 nm), yellow (∼520 nm) or red (∼628 nm). The effects of light on feeding, latency to begin feeding, growth and feed conversion were measured durin...

In this study, we show that the fish Nile tilapia displays an antipredator response to chemical cues present in the blood of conspecifics. This is the first report of alarm response induced by blood-borne chemical cues in fish. There is a body of evidence showing that chemical cues from epidermal 'club' cells elicit an alarm reaction in fish. Howev...

We investigated the effects of environmental light colors (blue, yellow and white) on the stress responses (measured by changes in ventilatory frequency - VF) of Nile tilapia to confinement. After 7 days of light treatment, the VF was similar for fish in each color. On the 8th day, fish were confined for 15min. After release, the post-confinement V...

We investigated the association of eye color with the dominantsubordinate relationship in the fish Nile tilapia, Oreochromis niloticus. Eye color pattern was also examined in relation to the intensity of attacks. We paired 20 size-matched fish (intruder: 73.69 +/- 11.49 g; resident: 75.42 +/- 8.83 g) and evaluated eye color and fights. These fish w...

This study analyzed the effects of noise levels and number of visitors on the behaviors of a mother puma and her daughter in a zoo environment with respect to the time of day. The study monitored visitation (noise and number) over two 1-week periods (4 weeks between periods) and frequency of various puma behaviors (videorecorded). The study analyze...

Approximately 50 years ago, Nile tilapia were accidentally introduced to Brazil, and the decline of pearl cichlid populations, which has been intensified by habitat degradation, in some locations has been associated with the presence of Nile tilapia. There is, however, little strong empirical evidence for the negative interaction of non-native fish...

This study reports on the temporal dynamics of feeding and reproduction of the damselfish, Stegastes fuscus in the coastal rocky reefs of northeastern Brazil. Water temperatures and rainfall data were registered and fish were captured on a monthly basis during one year. Fish body weights and lengths were measured and the stomachs were removed and c...

Eye darkening has been linked to social status in fish. The subordinate's eyes darken, while the eyes of the dominant fish become pale. Although this phenomenon has been described in salmonid fishes and in the African cichlid Nile tilapia Oreochromis niloticus, it is unclear whether eye darkening correlates with a reduction in aggressive behaviour....

Behavioural responses to stress can form distinct profiles in a wide range of animals: proactive and reactive profiles or coping styles. Stress responsiveness can also differentiate between the behavioural profiles. The tendency to regain feed intake following transfer to a novel social-isolation tank (the speed of acclimation) can discriminate bet...

In this work, I describe a logical method for scientific writing. Any decision made in this type of writing should be based on the logic of science and the rules of communication, as part of a creative discourse. I present some logical flaws (regarding journal classification, academic vs. non-academic texts, and subjective inferences) and writing m...

We investigated whether juveniles of the nocturnal fish jundiá (Rhamdia quelen) and the diurnal fish Nile tilapia (Oreochromis niloticus) are able to chemically communicate stress to conspecifics. Groups of 8 fish were reared in tanks under recirculated water (water exchanged among all the tanks) for each species. Fish were handled in half of the t...

Many studies show environmental enrichment is correlated with benefits to captive animals; however, one should not always assume this positive relationship given that enrichment increases the amount of resources that a territorial animal must defend and possibly affects its aggressive dynamics. In this study, we tested if environmental enrichment a...

Four substrata were offered to groups of adult Nile tilapia Oreochromis niloticus (one male and two females) simultaneously: pure sand, a mixture of sand and shells, stones and no substratum. The results showed that males chose to dig nests in a lighter and more homogeneous substratum.

We analyzed whether the position of students in classroom is correlated with academic performance, and which factors might be involved. The sample consisted of 16 classrooms in a school year bimester, each one with around 30 students. Each student's position was registered in classroom maps and the reasons for the students' seat choice were gathere...

The speckeld worm eel Myrophis punctatus lives in high-densities assemblages, and usually digs through, or lies on the substrate. These behaviours could lead to chemical marks on the substrate and could modulate the spatial distribution in this species. We tested the hypothesis that the spatial choice of the speckled worm eel is modulated by the pr...

We investigated the potential selective effect of fish ladders on physiological and morphological profiles of the curimbatá, Prochilodus lineatus, during reproductive migration in Brazil. We registered sex, body weight and length, plasma glucose, hepatosomatic and gonadosomatic indices (HSI and GSI, respectively), hematocrit, leucocrit, blood cell...

Reproductive fish behavior is affected by male-female interactions that stimulate physiological responses such as hormonal release and gonad development. During male-female interactions, visual and chemical communication can modulate fish reproduction. The aim of the present study was to test the effect of visual and chemical male-female interactio...

This study tested whether aggressive behaviour can predict individual variation in stress responses of Nile tilapia Oreochromis niloticus. We used a mirror test to measure tendency to aggressive behaviour, and calculated the attack frequency and time until the first attack (latency) for each fish. One day later, we measured plasma cortisol and gluc...

Después de una breve retrospectiva histórica de la ciencia del bienestar animal, en este artículo reconocemos la capacidad de sentir en animales no-humanos; pero enfatizamos que un problema crucial aun persiste al definir y medir el bienestar animal. Desalentamos el uso de medidas fisiológicas para evaluar el bienestar. Argumentamos que hay bases t...

Descriptions of feeling states in nonhuman animals have relied on indirect evidence from empirical data. Assumptions that fish do not experience suffering lack evidence and in fact contradict a large body of indirect scientific evidence and ethical concern. Why should the burden of proof rest on those defending the hypothesis that fish feel pain an...

We investigated interaction of the Nile tilapia, Oreochromis niloticus, paired with either a predator, spotted sorubim, Pseudoplatystoma corruscans, or a nonpredator, threespot leporinus, Leporinus friderici. Fish behaviors were quantified 5 min before pairing and 15 min during pairing (a heterospecific fish introduced into the Nile tilapia aquariu...

Body size and prior residence can modulate agonistic interaction in several animal species, but scientists know little about these relationships in echinoderms. In this study, we tested the effects of these traits on interactions in the black sea urchin (Echinometra lucunter). After a sea urchin was isolated for 24-h in a glass tank to establish pr...

The effect of chronic social stress on growth, energetic substrates and hormones was tested in rainbow trout, Oncorhynchus mykiss. After a 14-day isolation period, the fish were paired for 8 days. In order to expose fish to chronic intermittent social contact during pairing, they were maintained in direct contact with each other during the first da...

This study tested the adequacy of feeding as an unconditioned stimulus (US) to condition an endocrine response (plasma cortisol increase) in the cichlid fish Nile tilapia (Oreochromis niloticus). In a first study, conditioning was confirmed in grouped fish in the only experiment using single-held Nile tilapia. In this test a conditioned stimulus (C...

In a recent review on the concept of fish welfare, I argue that concern on fish welfare is definitively a genuine matter, and the main challenge is to find valid methodologies to evaluate this internal state in these animals. I also argue in that review that studies on fish preference should be emphasized, instead of frustrated attempts to empirica...

In a recent review on the concept of fish welfare, I argue that concern on fish welfare is definitively a genuine matter, and the main challenge is to find valid methodologies to evaluate this internal state in these animals. I also argue in that review that studies on fish preference should be emphasized, instead of frustrated attempts to empirica...

Fish welfare issues are predicated on understanding whether fish are sentient beings. Therefore, we analyzed the logic of the methodologies used for studying this attribute. We conclude that empirical science is unable to prove or to disprove that fish are sentient beings. Thus, we propose a combined ethical-scientific approach for considering fish...

In the present study, the effect of chemical factors released by conspecifics on growth variability (heterogeneous growth - HetG) in a gregarious fish species (Prochilodus lineatus) was tested. HetG was assessed by the weight variation coefficient in two consecutive 21-day periods. The fish were grouped in tanks (4 fish in each) that received runni...

The genotoxicity of the anaesthetic MS222 (tricaine) was analysed in fish under both invivo and invitro conditions. Based on results of the single cell gel/Comet assay, MS222 had no direct genotoxic effect on the experimental fish, indicating that MS222 does not induce primary DNA damage. These results suggest that the use of this important anaesth...

Plasma cortisol and glucose levels were measured in 36 adult Nile tilapia males, Oreochromis niloticus (standard length, mean ± SD, 14.38 ± 1.31 cm), subjected to electroshock and social stressors. Pre-stressor levels were determined 5 days after the adjustment of the fish to the experimental aquaria (1 fish/aquarium). Five days later, the effects...

Ventilatory frequency (VF) was investigated in the fish Nile tilapia, Oreochromis niloticus, subjected to confinement, electroshock or social stressor. Fish were allowed to acclimatize to tank conditions for 10 days (1 fish/aquarium). VF baseline was determined 5 days after adjustment had been started. At the 10th day of isolation, stressor effects...

Plasma cortisol and glucose levels were measured in 36 adult Nile tilapia males, Oreochromis niloticus (standard length, mean ± SD, 14.38 ± 1.31 cm), subjected to electroshock and social stressors. Pre-stressor levels were determined 5 days after the adjustment of the fish to the experimental aquaria (1 fish/aquarium). Five days later, the effects...

Following previously published observations that a conditioned response (CR) was lost more quickly by rainbow trout (Oncorhynchus mykiss) exhibiting a high responsiveness to stressors than by low responding individuals this study was designed to investigate the effects of exogenous cortisol on the retention of a CR in unselected rainbow trout. Fish...

Biological rhythms are one of the most intriguing and exciting research fields in biology. Aquatic organisms are not exceptions; many studies have been devoted to different kinds of rhythms these organisms show. Despite the immense literature on this topic, little is found regarding fishes—and even less regarding the tropical ones. This chapter dea...

The pintado (Pseudoplatystoma coruscans) is a ferocious carnivorous catfish with evident cannibalistic behaviour; its nocturnal habits are related to its ability to use predominately chemical sensorial modalities. This study investigated whether the pintado distinguishes conspecifics of different body sizes using chemical cues, which may reflect di...

This study tested the use of ventilatory frequency (VF) as an indicator of stress in the Nile tilapia, Oreochromis niloticus (L.). Firstly, we tested the relationship between VF and plasma cortisol after confinement. Confined fish showed higher VF and plasma cortisol levels, but the latter continued to increase significantly for longer time than VF...

We investigated the effects of environmental color on the reproductive behavior of Nile tilapia, Oreochromis niloticus. Two environmental colors were tested by covering the aquarium (60 x 60 x 40 cm) with white (12 groups) or blue (13 groups) cellophane and observing reproductive behavior in groups of 2 males (10.27 +/- 0.45 cm) and 3 females (10.7...

A Pavlovian conditioning paradigm was used to induce a connection between a conditioned stimulus, light (CS), associated with an unconditioned stimulus, confinement (US) in Nile tilapia Oreochromis niloticus, which resulted in a conditioned endocrine response (CR) to the CS alone manifested as an increase in plasma cortisol. Individual isolated Nil...

We investigated the association of eye color with the dominant-subordinate relationship in the fish Nile tilapia, Oreochromis niloticus. Eye color pattern was also examined in relation to the intensity of attacks. We paired 20 size-matched fish (intruder: 73.69 11.49 g; resident: 75.42 8.83 g) and evaluated eye color and fights. These fish were iso...

We discuss the main problems which make a scientific text difficult to find, to be read or to be accepted by readers. A scientific text is considered a logical argument. Therefore, methods, results and data from literature are premises supporting the conclusions of the work; and in the "Introduction" session, the justification corroborates the obje...

Discutimos os principais problemas que fazem com que um texto científico não seja encontrado, lido ou aceito pelos leitores. Um texto científico é considerado um argumento lógico. Portanto, métodos, resultados e dados da literatura são considerados premissas que suportam as conclusões do trabalho; e na sessão "Introdução", as justificativas corrobo...

Fish blood erythrocytes are frequently used as sentinels in biomonitoring studies. Usually, fish blood is collected by painful cardiac or caudal vein punctures. Previous anesthesia could decrease animal suffering but it is not known at present whether anesthesia can cause confounding effects. Therefore, using the alkaline single cell gel (SCG)/come...

Fish blood erythrocytes are frequently used as sentinels in biomonitoring studies. Usually, fish blood is collected by painful cardiac or caudal vein punctures. Previous anesthesia could decrease animal suffering but it is not known at present whether anesthesia can cause confounding effects. Therefore, using the alkaline single cell gel (SCG)/come...

Although the skin of an injured conspecific releases alarm substance in some fish species, it has been shown that such damage induces feeding behaviour rather than an alarm reaction under conditions of food scarcity. We studied chemical communication associated with this paradox in a Brazilian catfish, the pintado (Pseudoplatystoma coruscans). In p...

The present study aimed to test the effects of blue, green or white light on the stress response of the Nile tilapia, Oreochromis niloticus (L.). Each color was tested on two groups of isolated adult Nile tilapia (8 replicates each): one being subjected to confinement stress, and the other not (control). A different environmental color was imposed...

In this study we describe pacus, Piaractus mesopotamicus, detecting the presence of a predator by conspecific alerting pheromone. Moreover, we investigate whether this chemical information indicates the presence of a specific predator, or whether it indicates general disturbance. We exposed groups of pacus to the view of a predator fish (trahira, H...

Editorial of Annutal Review of Biomedical Sciences - volume 1, 1999.

This study examines the influence of early experience with different forms of aggressive behaviour on the fighting behaviour of young fish. Fry of the cichlid fish, Oreochromis niloticus, were raised from hatching in small groups consisting of a normal individual (the test fish) and either mutant conspecifics lacking the dorsal fin and thereby the...

The chemical modulation of agonistic behavior and conspecific recognition were tested in juveniles of the fish Nile tilapia, Oreochromis niloticus (L.). After a 7-day isolation period, the fish were grouped (four individuals per aquarium) for 7 days. Then fish of alpha and beta ranks (previously matched for similar size) were paired in a neutral te...

Metabolic differences derived from social stress usually show data with high variance that may hinder the finding of important differences. Since such high variance may be caused by agonistic variability occurring during social interactions, this work tested whether metabolism is associated with agonistic profile in the cichlid fish Nile tilapia, O...

Increase in heterogeneous growth as a result of grouping in the Nile tilapia, Oreochromis niloticus (L.), is presumed to be partially promoted by the social stress imposed by the dominant fish on the subordinates. Such stress may decrease the energy available for growth. In this study, the effect of social stress on carbohydrate metabolism was stud...

The fitness of the snatching frequency as an indicator of food intake in Nile tilapia fingerlings, Oreochromis niloticus (L), was studied. Five groups of four individuals each were used after a two-day starvation period. The hierarchical rank among individuals in the same group was registered. Food in the form of tiny pellets (ranging from 1.30 to...

1 DOCENTE-UNESP. 2 INICIAÇÃO CIENTÍFICA-UFRN. 3 DOCENTE – UFRN. INTRODUÇÃO Avanços recentes sobre o bem-estar animal têm estimulado pesquisas sobre fenômenos psicológicos em peixes, como motivação, emoção e cognição, curiosidade, diferenças entre peixes tímidos e extrovertidos, medo, personalidade, agressividade, aprendizagem, reconhecimento indivi...

No presente estudo avaliou-se a tese de que o grau hierárquico afeta os afeta os mecanismos de controle da coloração na tilápia-do Nilo, Oreochromis niloticus (L.). Para tanto, inicialmente avaliaram-se as ralações entre coloração do substrato na mediação da coloração corporal e seus efeitos na hierarquia de dominância; em seguida, testou-se se o g...