Biology subjects

Skandalis, D. A.

Publications and source records attributed to Skandalis, D. A..

5 recordsLinked to original sources

bioRxiv2023

Brain aromatase dynamics reflect parental experience and behaviour in male mice

In most mammals, paternal care is not mandatory for raising offspring. In house mice, experience with pups governs the extent and quality of paternal care. First-time fathers undergo a dramatic transition from ignoring or killing pups to caring for pups. The behavioral shift occurs together with changes in brain estrogen signaling as indicated by changes in estrogen receptor presence and distribution in multiple areas regulating olfaction, emotion, and motivation. Here, we report changes in the expression of aromatase, the enzyme converting testosterone into estrogen, as an indirect measure of estrogen synthesis. The amount of paternal experience (5 or 27 days) was associated with increased numbers of immunocytochemically-identified aromatase expressing cells in the medial and cortical amygdala, posterior piriform cortex, and ventromedial hypothalamus. Functionally, these changes can be related to the disappearance of aggression or neglect towards pups when first-time fathers or, even more, well-experienced fathers are handling their own pups. In the lateral septum, the anterior piriform cortex and to some extent in the medial preoptic area, parental experience increased the number of aromatase-positive cells only in fathers with 27 days of experience, and only in the right hemisphere. This is a new case of brain-functional lateralization due to experience that has activated certain instinctive behavior. Nuclei/areas associated with maternal care (medial preoptic area, bed nucleus of stria terminalis, nucleus accumbens) exhibited a left-hemisphere advantage in aromatase expressing cells, both in pup-naive and pup-experienced males. This newly found lateralization may contribute to the left-hemisphere dominant processing and perception of pup calls to release parental behavior. In general, the experience-dependent changes in aromatase expression we observed in most brain areas did not mirror the previously reported changes in estrogen receptors (ER) when pup-naive males became pup-caring fathers. Hence, paternal behavior may depend in a brain area-specific way on the differential action of estrogen through its receptors and/or direct local modulation of neural processing.

neuroscience↗

bioRxiv2023

The spatiotemporal richness of hummingbird wing deformations

Animals exhibit an abundant diversity of forms, and this diversity is even more evident when considering animals that can change shape on demand. The evolution of flexibility contributes to aspects of performance from propulsive efficiency to environmental navigation. It is, however, challenging to quantify and compare body parts that, by their nature, dynamically vary in shape over many time scales. Commonly, body configurations are tracked by labelled markers and quantified parametrically through conventional measures of size and shape (descriptor approach) or non-parametrically through data-driven analyses that broadly capture spatiotemporal deformation patterns (shape variable approach). We developed a weightless marker tracking technique and combined these analytic approaches to study wing morphological flexibility in hoverfeeding Annas hummingbirds (Calypte anna). Four shape variables explained >95% of typical stroke cycle wing shape variation and were broadly correlated with specific conventional descriptors like wing twist and area. Moreover, shape variables decomposed wing deformations into pairs of in- and out-of-plane components at integer multiples of the stroke frequency. This property allowed us to identify spatiotemporal deformation profiles characteristic of hoverfeeding with experimentally imposed kinematic constraints, including through shape variables explaining <10% of typical shape variation. Hoverfeeding in front of a visual barrier restricted stroke amplitude and elicited increased stroke frequencies together with in- and out-of-plane deformations throughout the stroke cycle. Lifting submaximal loads increased stroke amplitudes at similar stroke frequencies together with prominent in-plane deformations during the upstroke and pronation. Our study highlights how spatially and temporally distinct changes in wing shape can contribute to agile fluidic locomotion. SummaryHummingbirds exhibit complex wing deformations throughout the stroke cycle, and the timing and origin of these deformations differs between hoverfeeding behaviours.

zoology↗

bioRxiv2021

Corollary discharge prevents signal distortion and enhances sensing during locomotion

Sensory feedback during movement entails sensing a mix of externally- and self-generated stimuli (respectively, exafference and reafference). In many peripheral sensory systems, a parallel copy of the motor command, a corollary discharge, is thought to eliminate sensory feedback during behaviors. However, reafference has important roles in motor control, because it provides real-time feedback on the animals motions through the environment. In this case, the corollary discharge must be calibrated to enable feedback while avoiding negative consequences like sensor fatigue. The undulatory motions of fishes bodies generate induced flows that are sensed by the lateral line sensory organ, and prior work has shown these reafferent signals contribute to the regulation of swimming kinematics. Corollary discharge to the lateral line reduces the gain for reafference, but cannot eliminate it altogether. We develop a data-driven model integrating swimming biomechanics, hair cell physiology, and corollary discharge to understand how sensory modulation is calibrated during locomotion in larval zebrafish. In the absence of corollary discharge, lateral line afferent units exhibit the highly heterogeneous habituation rates characteristic of hair cell systems, typified by decaying sensitivity and phase distortions with respect to an input stimulus. Activation of the corollary discharge prevents habituation, reduces response heterogeneity, and regulates response phases in a narrow interval around the time of the peak stimulus. This suggests a synergistic interaction between the corollary discharge and the polarization of lateral line sensors, which sharpens sensitivity along their preferred axes. Our integrative model reveals a vital role of corollary discharge for ensuring precise feedback, including proprioception, during undulatory locomotion.

neuroscience↗

bioRxiv2020

Hydrogen sulfide exposure reduces thermal set point in zebrafish

Behavioural flexibility allows ectotherms to exploit the environment to govern their metabolic physiology, including in response to environmental stress. Hydrogen sulfide (H2S) is a widespread environmental toxin that can lethally inhibit metabolism. However, H2S can also alter behaviour and physiology, including a hypothesised induction of hibernation-like states characterised by downward shifts of the innate thermal setpoint (anapyrexia). Support for this hypothesis has proved controversial because it is difficult to isolate active and passive components of thermoregulation, especially in animals with high resting metabolic heat production. Here, we directly test this hypothesis by leveraging the natural behavioural thermoregulatory drive of fish to move between environments of different temperatures in accordance with their current physiological state and thermal preference. We observed a decrease in adult zebrafish (Danio rerio) preferred body temperature with exposure to 0.02% H2S, which we interpret as a shift in thermal setpoint. Individuals exhibited consistent differences in shuttling behaviour and preferred temperatures, which were reduced by a constant temperature magnitude during H2S exposure. Seeking lower temperatures alleviated H2S-induced metabolic stress, as measured by reduced rates of aquatic surface respiration rate. Our findings highlight the interactions between individual variation and sublethal impacts of environmental toxins on behaviour.

physiology↗

bioRxiv2019

Efferent Modulation Of Spontaneous Lateral Line Activity During And After Zebrafish Motor Commands

Accurate sensory processing during movement requires the animal to distinguish between external (exafferent) and self-generated (reafferent) stimuli to maintain sensitivity to biologically relevant cues. The lateral line system in fishes is a mechanosensory organ that experiences reafferent sensory feedback via detection of fluid motion relative to the body generated during behaviors such as swimming. For the first time in larval zebrafish (Danio rerio), we employed simultaneous recordings of lateral line and motor activity to reveal the activity of afferent neurons arising from endogenous feedback from hindbrain efferent neurons during locomotion. Frequency of spontaneous spiking in posterior lateral line afferent neurons decreased during motor activity and was absent for more than half of swimming trials. Targeted photoablation of efferent neurons abolished the afferent inhibition that was correlated to swimming, indicating that inhibitory efferent neurons are necessary for modulating lateral line sensitivity during locomotion. We monitored calcium activity with Tg(elav13:GCaMP6s) fish and found synchronous activity between putative cholinergic efferent neurons and motor neurons. We examined correlates of motor activity to determine which may best predict the attenuation of afferent activity and therefore what components of the motor signal are translated through the corollary discharge. Swim duration was most strongly correlated to the change in afferent spike frequency. Attenuated spike frequency persisted past the end of the fictive swim bout, suggesting that corollary discharge also affects the glide phase of burst and glide locomotion. The duration of the glide in which spike frequency was attenuated increased with swim duration but decreased with motor frequency. Our results detail a neuromodulatory mechanism in larval zebrafish that adaptively filters self-generated flow stimuli during both the active and passive phases of locomotion.

neuroscience↗