Alteration of cleaner wrasse cognition and brain morphology under marine heatwaves

Heatwaves, exacerbated by global warming, are progressively affecting various ecosystems, with coral reefs among the most susceptible. Within these ecosystems, cleaner wrasses (Labroides dimidiatus), engage in cooperative interactions with client fish by removing ectoparasites, and play an essential role in sustaining client abundance and diversity. In 2016, the northern section of the Great Barrier Reef experienced widespread and intense bleaching due to unparalleled ocean temperatures associated with a marine heatwave. While prior studies have connected changes in fish densities following this heatwave to modifications in cleaner fish cognitive performance, the immediate impact of heatwave exposure on cleaner fish cognition and brain structure has yet to be investigated. Here, we exposed cleaner wrasses to a laboratory-simulated Category 1 marine heatwave for 55 days, mirroring the 2016 Great Barrier Reef event. Cleaners’ cognitive performance was evaluated through a visual discr..., The dataset was collected from a laboratory experiment involving Bluestreak cleaner wrasses (Labroides dimidiatus; n=20), which were wild-caught in the Maldives and housed in flow-through aquaria at Laboratório Marítimo da Guia, Cascais, Portugal. Cleaners were exposed to two experimental treatments: control (28.8°C) and a simulated Category I marine heatwave (29.8°C). After a 5-day acclimation period, temperature was increased over 6 days to reach the target temperature for the heatwave treatment, and exposure lasted for 55 days. Afterward, a 30-day recovery period followed before brain dissection.
Behavioral trials, using an associative learning task (FAP test), were conducted at the end of the heatwave exposure and after a 14-day recovery period. Cleaners were tested individually on their ability to learn colour cues to locate a food reward, with up to 100 trials per fish.
Brain development was analyzed 30-days post exposure, with brains dissected into five regions and weighed for fu..., , # Alteration of cleaner wrasse cognition and brain morphology under marine heatwaves

[https://doi.org/10.5061/dryad.9zw3r22rn](https://doi.org/10.5061/dryad.9zw3r22rn)

## Description of the data and file structure

In this study, we investigate whether the response to environmental stress in a laboratory setting would parallel the observations of diminished strategic sophistication in cleaners, as reported by Triki et al. (2018) in the field. To explore this, individuals were subjected to a simulated Category 1 marine heatwave lasting 55 days, replicating the conditions of the 2016 El Niño event. Cleaners’ cognitive performance was evaluated through a visual discrimination task during the heatwave and after a 14-day recovery phase. This was followed by analysis of brain development 30 days after the cessation of the marine heatwave. The potential alignment of our laboratory findings with the field observations would imply that the impairment of cleaners’ cognitive abilities could be ...