Torres-Perez, J. V. | Search bioRxiv

bioRxiv2021

Characterising ontogeny of numerosity discrimination in zebrafish reveals multiple, numerical and non- numerical mechanisms.

A sense of non-symbolic numerical magnitudes is widespread in the animal kingdom and has been documented in adult zebrafish. Here we investigated the ontogeny of this ability using a group size preference task in juvenile zebrafish. Fish showed group size preference from 21 days post fertilization (dpf) and reliably chose the larger group when presented with discriminations of between 1 vs. 3, 2 vs. 5 and 2 vs. 3 conspecifics but not 2 vs. 4 conspecifics. When the ratio between the number of conspecifics in each group was maintained at 1:2, fish could discriminate between 1 vs. 2 individuals and 3 vs. 6, but again, not when given a choice between 2 vs. 4 individuals. These findings are in agreement with studies in other species suggesting the systems involved in quantity representation do not operate separately from other cognitive mechanisms. Rather they suggest quantity processing in fish may be the result of an interplay between attentional, cognitive and memory-related mechanisms as in humans and other animals. Our results emphasise the potential of the use of zebrafish to explore the genetic and neural processes underlying the ontogeny and function of number cognition.

animal behavior and cognition↗

bioRxiv2020

Stress reactivity elicits a tissue-specific reduction in telomere length in ageing zebrafish (Danio rerio)

Telomere length reflects cellular ageing. Increased telomere shortening in leukocytes is associated with a range of neurodegenerative and cardiovascular diseases, the onset and progression of which may be mediated by behavioural traits such as anxiety and stress reactivity. However, the effects of the hypothalamus-pituitary-adrenal axis stress response are shown to be tissue specific. As such, leukocyte telomere length may not give an accurate measure of the relationship between stress-reactivity and telomere length in disease relevant tissues. To test the hypothesis that stress-reactivity contributes to age-related telomere shortening in a tissue specific manner, we examined the correlation between telomere length in heart and brain tissue and stress-reactivity in a population of young (6-9 month) and ageing (18 month) zebrafish. Stress-reactivity was assessed by tank diving, a zebrafish version of the rodent open-field test, and through gene expression. Telomere length was assessed using quantitative polymerase chain reaction. We show that ageing zebrafish have shorter telomeres in both heart and brain. Telomere length is inversely related to stress-reactivity in heart but not brain of ageing individuals. These data support the hypotheses that an anxious predisposition contributes to telomere shortening in heart tissue, and by extension age-related heart disease, and that stress-reactivity contributes to age-related telomere shortening in a tissue-specific manner.

physiology↗