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The ontogeny and evolution of cleaner fish social cognition

English title The ontogeny and evolution of cleaner fish social cognition
Applicant Bshary Redouan
Number 192673
Funding scheme Project funding (Div. I-III)
Research institution Institut de Biologie Faculté des Sciences Université de Neuchâtel
Institution of higher education University of Neuchatel - NE
Main discipline Ecology
Start/End 01.08.2020 - 31.07.2024
Approved amount 872'469.00
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Keywords (5)

modelling; brain morphology; cognition; behavioural ecology; social behaviour

Lay Summary (German)

Lead
Hintergrund: Um Varianz im Sozialverhalten zwischen Individuen derselben Art und zwischen Arten besser zu verstehen, müssen zwei Zeitskalen miteinander verbunden werden: die evolutionäre Zeitskala bringt genetische Anpassungen, wohingegen Tiere Entscheidungen mit Hilfe von Wahrnehmung, Lernen und Gedächtnis treffen. Erstere untersuchen wir anhand zwischenartlicher Vergleiche, letztere anhand detaillierter Studien zur Ontogenese von Verhalten. Spieltheoretische Modelle, in denen Individuen lernen, die Lernprozesse aber von genetischen (evoluierbaren) Faktoren bestimmt werden, komplementieren den empirischen Ansatz.
Lay summary

Hintergrund: Um Varianz im Sozialverhalten zwischen Individuen derselben Art und zwischen Arten besser zu verstehen, müssen zwei Zeitskalen miteinander verbunden werden: die evolutionäre Zeitskala bringt genetische Anpassungen, wohingegen Tiere Entscheidungen mit Hilfe von Wahrnehmung, Lernen und Gedächtnis treffen. Erstere untersuchen wir anhand zwischenartlicher Vergleiche, letztere anhand detaillierter Studien zur Ontogenese von Verhalten. Spieltheoretische Modelle, in denen Individuen lernen, die Lernprozesse aber von genetischen (evoluierbaren) Faktoren bestimmt werden, komplementieren den empirischen Ansatz.

Projektziele: Unsere empirische Forschung konzentriert sich auf Putzerlippfische. Die Putzer entfernen Ektoparasiten von anderen Rifffischen, bevorzugen allerdings die schützende Schleimschicht der Kunden. Wir untersuchen, wie sich Varianz in der Komplexität der zwischenartlichen sozialen Umgebung und/oder Konkurrenz zwischen Putzern auf die Entwicklung des Hirnes und die kognitiven Fähigkeiten auswirkt. Die Datenerhebung beruht zum einen auf Langzeitbeobachtungen von Individuen im Freiland, gefolgt von kognitiven Experimenten und Hirnanalysen, zum anderen auf Aufzuchtexperimenten im Labor. Der theoretische Teil des Projekts beinhaltet die Entwicklung von Evolutions-Modellen zu Entscheidungsregeln, basierend auf unseren empirischen Erkenntnissen.           

Wissenschaftlicher und gesellschaftlicher Kontext Das Projekt sollte uns wertvolle neue Erkenntnisse liefern, welche Umweltfaktoren Selektion auf die Entwicklung (Ontogenese) und/oder Evolution (Phylogenese) komplexer Hirne ausüben. Von besonderem Interesse ist das komplexe Sozialverhalten unserer Fische, das wichtige Fragen betreffend der Grundlagen tierischer Intelligenz aufwirft.  

Direct link to Lay Summary Last update: 20.08.2020

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Associated projects

Number Title Start Funding scheme
173334 How proximate factors underlying decision making may affect the evolution and maintenance of cooperation 01.05.2017 Project funding (Div. I-III)
197884 Acts of Assistance: Solving the riddle of stable cooperation among non-relatives in nonhuman primates 01.05.2021 Project funding (Div. I-III)

Abstract

The marine cleaning mutualism involving the cleaner wrasse Labroides dimidiatus and its ‘client’ reef fishes has become a textbook example for both testing evolutionary game theory on cooperation between unrelated individuals and for the ecological approach to cognition. A conflict of interest over what cleaner should eat - clients want ectoparasites removed while cleaners prefer to eat the clients’ protective mucus - apparently selected for cleaners being able to fine-tune their decisions to a great variety of contextual factors, i.e. they show high strategic sophistication. However, there is also large variation between cleaner fish individuals with respect to their strategic sophistication. These results raise three large questions of broad interest that will be the focus of the current grant application. First, we will investigate to what extent the logic of the social brain hypothesis can be applied to explain variation in brain complexity within a fish species. As a related second major question, we will test the Machiavellian intelligence hypothesis that predicts that social complexity promotes cognitive performance. Our cleaner fish species shows strong variation in relative forebrain size within a genetically well-mixed population, making it an ideal species to combine the social brain hypothesis and the Machiavellian intelligence hypothesis in a single study. Third, while it is well established that endotherm vertebrate clades (mammals and birds) have about ten times larger brains corrected for body size than ectotherm vertebrate clades (fishes, amphibians and reptiles), it is currently unclear what improved cognitive abilities such an enlarged brain provides to endotherms. Cleaner fish are particularly puzzling as their social cognition appears to be outstanding for a fish while their brain size is rather average. To address the three major questions, four work packages are proposed. The first involves long-term field observations of marked cleaner fish individuals, as is standard in research on mammals and birds but not on fishes. We will record in detail both intra- and interspecific social interactions and reconstruct the habitat in 3D. Survival, growth patterns and spawning events will be indicators of individual success. Selected individuals will then be subjected to various cooperation and cognition tasks in the laboratory before we quantify relative forebrain size and count cells in different brain regions. Sampling the brains of wild caught wrasse species that have the same social system as cleaners but whose local densities do not correlate with cleaner densities will allow us to investigate how local population density and habitat complexity affect brain development in the absence of cleaning interactions. The second work package will involve the development of a skinner box for fishes. With this efficiency enhancing tool, we can raise cleaner juveniles in captivity and vary the challenges they face to optimise their food intake. We can then test in how far such variation causes variation in the performance in cognitive tasks as well as brain features. Raising other wrasse species in the same way will allow testing in how far the strategic sophistication of cleaners is a mere function of exposure or due to specific adaptations. The third work package involves cleaners being subjected to laboratory experiments developed largely in primatology to test for the presence/absence of cognitive processes that supposedly demand increased processing power, like perspective taking, transitive inference, and building blocks of so-called general intelligence, i.e. the correlated expression of cognitive tools that can be used in both social and environmental contexts. Determining in detail the cognitive tool kit of cleaners may inform us which cognitive processes may only require a small brain and which may be too complex for ectotherm brains. The final work package aims to develop game-theoretical models of cooperation that are explicit about the underlying cognitive mechanisms. For example, what social environments select for the chunking of separate cues into larger units? Models will be explicitly linked with our empirical data, providing a powerful framework to study social cognition on both ecological and evolutionary time scales. Together, the four work packages will allow a strong integration of proximate and ultimate questions to advance our knowledge on brain evolution, social cognition and cooperation, with a strong focus on explaining variation within and across species. Results will therefore be of interest to a diversity of disciplines, including animal cognition, behavioural ecology, and evolutionary social sciences.
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