Quantity discrimination in angelfish, Pterophyllum scalare: a novel approach with food as the discriminant

311637, NSERC, Natural Sciences and Engineering Research Council of Canada; Ministerio de Economía, Industria y Competitividad, Gobierno de Españ

The Role of Body Surface Area in Quantity Discrimination in Angelfish (Pterophyllum scalare)

Although some fish species have been shown to be able to discriminate between two groups (shoals) of conspecifics differing in the number of members, most studies have not controlled for continuous variables that covary with number. Previously, using angelfish (Pterophyllum scalare) we started the systematic analysis of the potential influence of such continuous variables, and found that they play different roles in shoal discrimination depending on whether large (≥ 4 fish) or small (<4 fish) shoals were contrasted. Here, we examine the potential role of the overall body surface area of stimulus fish in shoal preference, a prominent variable not yet examined in angelfish. We report that both when numerically large (5 versus 10 fish) and when small (2 versus 3 fish) shoals were contrasted, angelfish were unable to discriminate the numerically different shoals as long as the surface area of the contrasted shoals was equated. Thus, we conclude that body surface may be an important continuous variable in shoal discrimination. This conclusion was further supported by the analysis of preference when shoals of the same numerical size but different body surface area were contrasted. We found subjects to spend significantly more time close to the shoals with the greater overall surface area. Last, we conducted an experiment in which we simultaneously controlled a set of continuous variables, including overall surface area, and found angelfish to use the number of shoal members as a cue only in large shoal contrasts but not in small shoal contrasts. This result suggests the potential existence of different processing systems for large and small numbers in fish

Zebrafish, a Potential Novel Research Tool for the Analysis and Modeling of Anxiety

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Tribal brains in the global village: Deeper roots of the pandemic

I briefly recap the messages of the target article by Wiebers & Feigin (2020) and the accompanying peer commentaries about what we learn from the COVID-19 pandemic. Using the rapid evolution of viruses as an example of the importance of prevention, I explore why it is difficult for our species to foresee and prevent unintended global changes resulting from human activity. I end with a discussion about the long-term future, the ultimate problem inherent in our current mindset and the structure of our economy: growth

Learning, memory, cognition, and the question of sentience in fish

Evolutionarily conserved features have been demonstrated at many levels of biological organization across a variety of species. Evolutionary conservation may apply to complex behavioral phenomena too. It is thus not inconceivable that a form of sentience does exist even in the lowest order vertebrate taxon, the teleosts. How similar it is to human sentience in its level of complexity or in its multidimensional features is a difficult question, especially from an experimental standpoint, given that even the definition of human sentience is debated. Woodruff attempts a Turing-like test of fish sentience, and lists numerous neuroanatomic, neurophysiological and behavioral similarities between fish and humans. In this commentary, I add to these similarities by discussing empirical findings showing complex forms of mental representation in fish. At the same time, I note that without a more thorough understanding of human sentience and more data on similarities as well as differences between fish and mammals, the final conclusion may have to wait

Sentience: All or none or matter of degree?

The question of whether fish feel pain is muddied by anthropomorphic thinking. Comparing biological phenomena in two species should be informed by the criteria for good animal models: face validity, construct validity and predictive validity. Viewed through this lens, we argue that fish do feel pain and may possess some level of sentience. Evolutionary relatedness, hence similarities and differences between species (fish and humans in this case), are not about black vs. white but about shades of grey

Food Quantity Discrimination in Angelfish (Pterophyllum scalare): The Role of Number, Density, Size and Area Occupied by the Food Items

Quantity discrimination, the ability to identify, process, and respond to differences in number, has been shown in a variety of animal species and may have fitness value. In fish, the ability to distinguish between numerically different shoals has been well studied. However, little work has been devoted to the investigation of such ability in a foraging context. Nevertheless, angelfish (Pterophyllum scalare) have been previously shown to be able to discriminate numerically different sets of food items, with variables such as size and density of the food items playing important roles in making the choice. Here, we examine the possible role of other numerical and non-numerical variables. Using a spontaneous binary choice task, we contrasted sets of food items differing in specifically controlled ways: (1) different numerical size but equal inter-item distance; (2) different numerical size and different inter-item distance; and (3) identical total contour length and area occupied but different individual food size and inter-food distance between the contrasted food sets. In Experiment 1, angelfish were found to prefer the sets with a large number of food items. In Experiment 2, they preferred the numerically smaller sets with clustered items to the numerically larger sets with scattered items, but only when the sets were in the large number range (10 vs. 5 food items). Finally, in Experiment 3 fish preferred numerically smaller sets with large-sized and scattered food items in the large number range sets. We conclude that food item number, density, and size may not be considered individually by angelfish, but instead, the fish respond to all these factors attempting to maximize energy gained from eating the food while minimizing energy expenditure collecting and/or protecting the foodThis research was supported by Grant MINECO-17-PSI2016-78249-P from the Ministerio de Economía, Industria y Competitividad (Spain) to LG-L, and Natural Sciences and Engineering Research Council of Canada (NSERC; Canada) Discovery Grant (311637) to RG

Parallel Mechanisms for Visual Search in Zebrafish

This research was funded by project grant G1000053 from the National Centre for the Replacement, Reduction and Refinement of animals in research (NC3Rs; UK) and by the Medical Research Council (MRC; UK). CHB is a Royal Society (UK) Research Fellow

Video playback versus live stimuli to assess quantity discrimination in angelfish (Pterophyllum scalare)

This research was supported by grant PSI2016-78249-P from the Ministerio de Economía y Competitividad (Spain) to L.M.G.-L., and an NSERC (Canada) Discovery grant (311637) to R.G