Biology subjects

Sakagiannis, P.

Publications and source records attributed to Sakagiannis, P..

4 recordsLinked to original sources

bioRxiv2024

Fast and recurrent evolution of temperature preference among drosophilids

Small-bodied ectotherms are acutely vulnerable to temperature changes, but diverse thermotactic behaviours have contributed to their ability to inhabit broad climatic niches. Understanding how - and how quickly - these behaviours evolve are outstanding biological questions that are also relevant to conservation. Among insects, Drosophila melanogaster is a preeminent ectothermic model for temperate sensing and thermotaxis. However, little is known about how its temperature-related behaviours have evolved in comparison to its closely related species. We have thermo-profiled over 2400 larvae from eight closely related species of Drosophila from different thermal habitats. Consistent with local adaptation, we found substantial variation in temperature preference and fine-scale navigational behaviours amongst these species. Agent-based modelling of the larval thermotaxis circuit suggests that it is the balance between cool and warm avoidance circuits, rather than changes in temperature sensitivity, that drive differences in temperature preference. Our findings highlight the recurrent evolution of temperature-related behaviours in an experimentally tractable cross-species system.

evolutionary biology↗

bioRxiv2023

Feeding-state dependent modulation of reciprocally interconnected inhibitory neurons biases sensorimotor decisions in Drosophila

Animals feeding state changes behavioral priorities and thus influences even non-feeding related decisions. How is the feeding state information transmitted to non-feeding related circuits and what are the circuit mechanisms involved in biasing non-feeding related decisions remains an open question. By combining calcium imaging, neuronal manipulations, behavioral analysis and computational modeling, we determined that the competition between different aversive responses to mechanical cues is biased by feeding state changes. We found that this is achieved by differential modulation of two different types of reciprocally connected inhibitory neurons promoting opposing actions. This modulation results in a more frequent active type of response and less frequently a protective type of response if larvae are fed sugar compared to when they are fed a balanced diet. The information about the internal state is conveyed to the inhibitory neurons through homologues of the vertebrate neuropeptide Y known to be involved in regulating feeding behavior.

neuroscience↗

bioRxiv2022

Prediction error drives associative olfactory learning and conditioned behavior in a spiking model of Drosophila larva

Predicting reinforcement from the presence of environmental clues is an essential component of guiding goal-directed behavior. In insect brains, the mushroom body is central to learning the necessary associations between sensory signals and reinforcement. We propose a biologically realistic spiking network model of the Drosophila larva olfactory pathway for the association of odors and reinforcement to bias behavior towards approach or avoidance. We demonstrate that prediction error coding through the integration of currently present and expected reinforcement in dopaminergic neurons can serve as a driving force in learning that can, combined with a synaptic homeostasis mechanism, account for experimentally observed features of acquisition and loss of associations in the larva that depend on the intensity of odor and reinforcement and temporal features of their pairing. To allow direct comparisons of our simulations with behavioral data [1], we model learning-induced plasticity over the complete time course of behavioral experiments and simulate the locomotion of individual larvae towards or away from odor sources in a virtual environment.

neuroscience↗

bioRxiv2020

A plausible mechanism for Drosophila larva intermittent behavior.

The behavior of many living organisms is not continuous. Rather, activity emerges in bouts that are separated by epochs of rest, a phenomenon known as intermittent behavior. Although intermittency is ubiquitous across phyla, empirical studies are scarce and the underlying neural mechanisms remain unknown. Here we present the first empirical evidence of intermittency during Drosophila larva free exploration. We report power-law distributed rest-bout and log-normal distributed activity-bout durations. We show that a stochastic network model can transition between power-law and non-power-law distributed states and we suggest a plausible neural mechanism for the alternating rest and activity in the larva. Finally, we discuss possible implementations in behavioral simulations extending spatial Levy-walk or coupled-oscillator models with temporal intermittency.

animal behavior and cognition↗