Graetsch, S. | Search bioRxiv

bioRxiv2025

Cognitive ethology of nest building in a shell-dwelling cichlid

Across animal taxa, nest-building behavior is performed using a generalizable and flexible mental representation of an action sequence - a schema. In order to accomplish its goal (a stable nest), the brain appears to compare intermediate steps in the process to stored mental images, or templates. Deviations from these templates drive progress, preferences, and corrections in the execution of this behavior. The stereotypy vs. plasticity of both schema and mental templates have rarely been defined in an experimentally accessible system. Here we investigated nest building by the cichlid Lamprologus ocellatus, a fish species that manipulates abandoned snail shells to build shelters for breeding and protection. We find that nest building is composed of a sequence of behaviors that are tied together by a series of stimulus-response loops, allowing for restarts and shortcuts as the behavioral program unfolds. The attraction to a shell object is innate, as is the final appearance of the nest. The behavior in an inexperienced animal is initially uncoordinated, but is fine-tuned by repeated building opportunities. Shells need to conform to rigid geometric criteria in order to be acceptable as a potential home. Nest building is accompanied by focused neural activity in brain regions homologous to the mammalian hippocampus and neocortex. In conclusion, we have uncovered the constraints and flexibility of cognitive template matching underlying an instinctive, goal-directed behavior.

animal behavior and cognition↗

bioRxiv2023

Brood care in shell-dwelling cichlids is timed by independent maternal and larval clocks

Successful brood care requires a finely tuned interplay between caregiving parent and offspring. Cichlids are a diverse group of teleost fish known for their extensive parental care of altricial young. Female Lamprologus ocellatus lay their eggs in the protective confines of an abandoned snail shell, where they raise them to free-swimming larvae. Here we investigated whether the transition to larval independence is driven by the behavior of the mother, the offspring, or an interaction between the two. Using 3D printed shells with a window, we were able to observe the behavior of both mother and offspring inside the nest using automated object detection and tracking. We found that, once hatched, the larvae remain in the deep chambers of the shell, and at 9 dpf, actively emerge from the shell during the day. An inversion of larval phototactic behavior from dark- to light-seeking leads up to this emergence. Removal of the mother causes premature emergence of the larvae by a few days. The natural schedule (emergence at 9 dpf) is restored if the larvae are supplied with fresh water in the mothers absence. In cross-fostering experiments, we found that swapping out the mothers own clutch for older larvae forces a delay in emergence, as the foster mother prevents the larvae from leaving at 9 dpf. We conclude that larval and maternal behavior are each controlled by independent internal clocks, which, although normally synchronized, can be experimentally manipulated and brought into conflict. This study has thus revealed an innate sequence of behavioral adaptations that orchestrate brood care in shell-dwelling cichlids.

evolutionary biology↗