ABOUT ME
I am largely interested in the ways that animals respond to changes in their environment; particularly those pertaining to the social environment. My research typically incorporates multiple disciplines (e.g., physiology, molecular biology, behavioural ecology) in an effort to attain an integrative understanding of the question at hand.
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While I primarily work with fishes, I have also conducted studies with bees and frogs in the past.
RESEARCH INTERESTS
Roles of the Corticotropin-Releasing Factor System​
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While the corticotropin-releasing factor (CRF) system is best known for its role in regulating glucocorticoid synthesis (Best et al., 2024), the CRF system has several other important functions both in the brain and peripheral tissues. In particular, the CRF system is thought to have an evolutionarily conserved role in regulating water and ion balance across vertebrates and invertebrates.
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The focus of my PhD thesis is to explore the various contributions of the CRF system during osmotic challenges in fishes, both centrally in the brain (e.g., corticotrope and thyrotrope regulation; Culbert et al., 2022) and in peripheral tissues (e.g., gills and intestine). Owing to additional genome duplications, the CRF system in most fishes is more complex than in other vertebrate groups meaning that there is still much to learn about the regulation and functions of this important neuropeptide system.
Schematic of the corticotropin-releasing factor (CRF) system in teleost fish
Physiological Consequences of the Social Environment
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I am quite interested in the effects that an animal's current and past social experiences have on their physiology. Much of this work has centered around the effects of social rank on glucocorticoid production.
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Animals that live in groups typically form social hierarchies to determine access to limited resources (e.g., shelter, reproductive opportunities). Individuals at the top of these hierarchies (i.e., dominants) suppress individuals at the bottom (i.e., subordinates) through the use of aggression. The physiological costs of subordination can include elevated production of glucocorticoids, impaired reproductive capacity, dysregulated oxidative balance, reduced food intake, and lower growth rates than dominants. We have explored how these effects are influenced by an animal's social environment under relatively simple (e.g., dyads of rainbow trout (Culbert & Gilmour, 2016; Kostyniuk et al., 2018, Mennigen et al., 2022; Best et al., 2023) and dyads of pygmy halfbeaks (Reuland et al., 2021)), as well as more complex (e.g., social groups of Neolamprologus pulcher; Culbert et al., 2018, 2019, 2022) social settings in the laboratory. Recently, we travelled to Lake Tanganyika in Zambia to evaluate how glucocorticoids (Culbert et al., 2021) and socially-implicated neuropeptide systems, such as arginine vasotocin, isotocin, and galanin (Culbert et al., 2022; Culbert et al., 2024), are regulated in wild groups of N. pulcher.
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Additionally, we have investigated more complex relationships between an animal's physiology and their social environment. For example, we found that glucocorticoid levels of acutely stressed N. pulcher are lower when individuals recover with their social group compared to when they recover by themselves (Culbert et al., 2019). We have also shown that, unlike in mammals, cortisol does not promote prosociality in wild groups of N. pulcher (Culbert et al., 2021). Most recently, we explored how an individual's social rank influences relationships between their hormone levels and levels of oxidative stress in a lekking cichlid, Astatotilapia burtoni (Culbert et al., 2023).
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I discussed some of this work with Alex Evans on behalf of the Society of Experimental Biology.
A social group of Neolamprologus pulcher
Observing fish behaviour while SCUBA diving in Lake Tanganyika
Role of Visual Signals during Social Interactions
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I am also interested in the roles that visual signals play under different social contexts. Many animals use visual signals to advertise their quality (colourful; carotenoid-based) and/or aggressive intentions (dark; melanin-based). I am particularly interested in the social regulation of melanin-based signals, as they are often regulated by pathways that are also involved in the production of glucocorticoids (e.g., the melanocortin system).
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While there is a substantial body of literature on the roles of social signals in birds, there has been comparatively less research on the roles of social signals in fish. We have shown that social groups of N. pulcher display status-specific responses to territory intruders based on the intensity of the intruder's melanin-based facial stripes (Culbert & Balshine, 2019). We also found that N. pulcher exhibit a strong interaction bias towards yellow items—which influences their performance on an associative learning task—but affiliative decisions in the lab were not influenced by the amount of yellow on the faces of conspecifics (Culbert et al, 2020). However, in the wild we found that the size of these yellow facial patches increased with foraging and that patch size had social status-specific associations with affiliative relationships between groupmates (Culbert et al., 2023).
Additionally, we found that the preferences of female pygmy halfbeaks for red colouration on males varies based on their sexual and social experience (Reuland et al., 2019).
N. pulcher have distinctive markings on their faces
