Biology subjects

Fritschi, L.

Publications and source records attributed to Fritschi, L..

3 recordsLinked to original sources

bioRxiv2026

Social and environmental cues mask circadian activity patterns in a highly social shell-dwelling cichlid fish

Species exhibit variation in their circadian activity rhythms, including being active during the day (diurnal), the night (nocturnal), or the twilight periods (crepuscular). While the influence of environmental factors such as light on entraining and controlling activity patterns is well known, it is unclear how social and abiotic factors affect circadian behaviors. The daily activity patterns of Lake Tanganyikan cichlid fish are diverse, and may be associated with species diversification. Intriguingly, some shell-dwelling cichlid species, which anecdotal observation suggests are diurnal, displayed strong nocturnal activity when assayed in a "common garden" lab setup. Here, by integrating field and lab-based studies, we provide three lines of evidence that social and environmental cues mask underlying circadian rhythms in shell-dwelling cichlids. First, we demonstrate that shell-dwelling cichlids are diurnal in their natural habitat, but convert to nocturnal activity when assayed alone in a common garden. Second, we identify that in the presence of a shell and conspecifics the highly social N. multifasciatus becomes diurnal. In contrast, the circadian activity pattern of a closely related, but sub-social species, N. brevis, is masked only by a shell, and unaffected by the presence of conspecifics. Third, we demonstrate that the masking effect of shells and conspecifics is circadian and continues in the absence of light. Fourth, we identify that the response to these cues is influenced by sex, with greater effects in female fish, and by pedigree, with stronger effects in individuals bred and raised in captivity compared to those captured in the wild. Together, these experiments reveal new relationships between circadian rhythms and sociality in these fishes, offering broader insights into the ecological and evolutionary drivers of these behaviours.

animal behavior and cognition↗

bioRxiv2024

Widespread temporal niche partitioning in an adaptive radiation of cichlid fishes

The partitioning of ecological niches is a fundamental component of species diversification in adaptive radiations. However, it is presently unknown if and how such bursts of organismal diversity are influenced by temporal niche partitioning, wherein species avoid competition by being active during different time windows. Here, we address this question through profiling temporal activity patterns in the exceptionally diverse fauna of cichlid fishes from African Lake Tanganyika. By integrating week-long longitudinal behavioural recordings of over 500 individuals from 60 species with eco-morphological and genomic information, we provide two lines of evidence that temporal niche partitioning facilitated this massive adaptive radiation. First, Tanganyikan cichlids exhibit all known circadian temporal activity patterns (diurnal, nocturnal, crepuscular, and cathemeral) and display substantial inter-specific variation in daily amounts of locomotion. Second, many species with similar habitat and diet niches occupy distinct temporal niches. Moreover, our results suggest that shifts between diurnal and nocturnal activity patterns are facilitated by a crepuscular intermediate state. In addition, genome-wide association studies indicate that the genetics underlying activity patterns is complex, with different clades associated with different combinations of variants. The identified variants were not associated with core circadian clock genes but with genes implicated in synapse function. These observations indicate that temporal niche partitioning contributed to adaptive radiation in cichlids and that many genes are associated with the diversity and evolution of temporal activity patterns.

evolutionary biology↗

bioRxiv2023

Parameter Inference for an Astrocyte Model using Machine Learning Approaches

Astrocytes are the largest subset of glial cells and perform structural, metabolic, and regulatory functions. They are directly involved in the communication at neuronal synapses and the maintenance of brain homeostasis. Several disorders, such as Alzheimers, epilepsy, and schizophrenia, have been associated with astrocyte dysfunction. Computational models on various spatial levels have been proposed to aid in the understanding and research of astrocytes. The difficulty of computational astrocyte models is to fastly and precisely infer parameters. Physics informed neural networks (PINNs) use the underlying physics to infer parameters and, if necessary, dynamics that can not be observed. We have applied PINNs to estimate parameters for a computational model of an astrocytic compartment. The addition of two techniques helped with the gradient pathologies of the PINNS, the dynamic weighting of various loss components and the addition of Transformers. To overcome the issue that the neural network only learned the time dependence but did not know about eventual changes of the input stimulation to the astrocyte model, we followed an adaptation of PINNs from control theory (PINCs). In the end, we were able to infer parameters from artificial, noisy data, with stable results for the computational astrocyte model.

biophysics↗