Biology subjects

Fusani, L.

Publications and source records attributed to Fusani, L..

6 recordsLinked to original sources

bioRxiv2025

Nutritional state and predator exposure jointly mediate stress resilience and behavioural flexibility

Behavioral flexibility plays an important role in adaptation to changing environments within an individuals lifetime. Stress resilience influences flexibility, as short-term stress can enhance attention and memory, while prolonged stress may impair cognitive function. Nutritional state also plays a role, with overweight individuals often suffering greater consequences of chronic stress. The allostatic load model predicts that individuals under prolonged stress remain in a chronically activated state, potentially reducing flexibility. Using a cichlid, we manipulated body condition and exposed individuals to occasional or frequent predator presentations. We then assessed stress responses and behavioral flexibility via a reversal learning test. Contrary to predictions, fish in a high nutritional state - but not overweight - that were frequently exposed to predators recovered rapidly from stress and exhibited enhanced flexibility. Our results provide direct evidence that nutritional state interacts with behavioral flexibility, revealing the costs of coping with repeated stressors. We highlight a link between brief stress responses, characterized by rapid cortisol recovery, and behavioral flexibility. This association only emerged in well-nourished individuals facing frequent stressors, suggesting energy reserves buffer the costs of repeated stress. Thus, resilience benefits behavioral flexibility, while it is energetically costly, as a reduced diet hindered adaptation to environmental change.

animal behavior and cognition↗

bioRxiv2023

The role of the stress axis in mediating behavioural flexibility in a social cichlid, Neolamprologus pulcher

Behavioural flexibility plays a major role in the way animals cope with novel situations, and physiological stress responses are adaptive and highly efficient mechanisms to cope with unpredictable events. Previous studies investigating the role of stress responses in mediating behavioural flexibility were mostly done in laboratory rodents using stressors and cognitive challenges unrelated to the ecology of the species. To better understand how stress mediates behavioural flexibility in a natural context, direct manipulations of the stress response and cognitive tests in ecologically relevant contexts are needed. To this aim, we pharmacologically blocked glucocorticoid receptors (GR) in adult Neolamprologus pulcher using a minimally invasive application of a GR antagonist. GR blockade prevents the recovery after a stressful event, which we predicted to impair behavioural flexibility. After the application of the GR antagonist, we repeatedly exposed fish to a predator and tested their behavioural flexibility using a detour task, i.e. fish had to find a new, longer route to the shelter when the shortest route was blocked. While the latencies to find the shelter were not different between treatments, GR blocked fish showed more failed attempts during the detour tasks than control fish. Furthermore, weak performance during the detour tasks was accompanied by an increase of fear related behaviours. This suggests that blocking GR changed the perception of fear and resulted in an impaired behavioural flexibility. Therefore, our results support a causal link between the capacity to recover from stressors and behavioural flexibility in N. pulcher with potential consequences for an effective and adaptive coping with changing environments.

animal behavior and cognition↗

bioRxiv2023

The unexpected loss of the "hunger hormone" ghrelin in true passerines: A game changer in migration physiology

Migratory birds must accumulate large amounts of fat prior to migration to sustain long flights. In passerines, the small body size limits the amount of energy stores that can be transported and therefore birds undergo cycles of extreme fattening and rapid exhaustion of reserves. Research on these physiological adaptations was rattled by the discovery that birds have lost the main vertebrate regulator of fat deposition, leptin. Recent studies have thus focused on ghrelin, known as the "hunger hormone", a peptide secreted by the gastrointestinal tract to regulate food intake, body mass, and other important functions in vertebrates. Studies on domestic species showed that in birds ghrelin has effects opposite to those described in mammals, such as inhibiting instead of promoting food intake. Furthermore, a series of recent studies have shown that ghrelin administration influences migratory behaviour in passerine birds, suggesting an important role of this hormone in bird migration. However, using comparative genomic analyses we show that ghrelin has been lost in the largest avian taxon Eupasseres, after the basic split from Acanthisitti about 50 million years ago. Eupasserines, also known as True passerines, include all but two of the ca. 10,000 known passerine species. We further found that the ghrelin receptor (growth hormone secretagogue receptor, GHS-R) is still conserved in passerine birds, as indicated by sites under purifying selection and in line with the effects of ghrelin administration. Thus, ghrelin adds to a list of hormones highly conserved in vertebrates that have lost their main functions in specific taxa. The maintenance of a functional receptor system, however, suggests that in eupasserine birds another ligand has replaced ghrelin, perhaps to bypass the feedback system that would hinder large pre-migratory accumulation of subcutaneous fat.

evolutionary biology↗

bioRxiv2023

Controlled expression of avian migratory fattening influences innate immune responses

While immunity is frequently suppressed when birds engage in strenuous migratory flights, whether and how immunity changes during the rapid accumulation of energy stores in preparation for migration remains largely unknown. Here, we induced pre-migratory fattening through controlled changes of daylight in common quails Coturnix coturnix and regularly assessed changes in a marker of constitutive innate immunity (Leukocyte Coping Capacity or LCC) and measures of body composition (lean and fat mass). LCC responses were highest in the mid-fattening phase and lowest when fattening was completed. At mid-fattening, we also found that the birds that kept a higher proportion of lean mass (i.e. accumulated less fat) had the highest LCC peaks. Our results indicate that migratory birds undergo rapid immunological changes as they accumulate energy stores for migration and propose that this could be due to competing or trade-off processes between metabolic remodelling and innate immune system function. Summary statementImmunity is vital when migrating to new environments. It is costly and competivite to other physiological processes. Here we bring new evidence on this process in migratory birds.

physiology↗

bioRxiv2022

Sex differences in migration timing influence the network structure of avian assemblages at a stopover site

Migratory species are changing the timing of departures from wintering areas and arrival to breeding sites (i.e., migration phenology), as response to climate change to exploit maximum food availability at higher latitudes and improve their fitness. Despite the impact of changing migration phenology on migratory connectivity at population and community level, the extent to which such individual and species-specific response affects associations among co-migrating species has been seldom explored. By applying temporal co-occurrence network models on 15 years of standardized bird ringing data at a spring stopover site, we show that African-European migratory landbirds tend to migrate in well-defined groups of species with high temporal overlap. Such co-migration fidelity is significantly increasing over the years and higher in trans-Saharan than North-African migrants. Our findings suggest non-random patterns of associations in co-migrating species, possibly related to the existence of regulatory mechanisms associated with changing climate conditions and different uses of stopover sites by migrants, ultimately influencing the global migration economy of landbirds in the Palearctic-African migration system.

ecology↗

bioRxiv2020

Androgen responsiveness to simulated territorial intrusions in Allobates femoralis males: evidence supporting the challenge hypothesis in a territorial frog

Territorial behaviour has been widely described across many animal taxa, where the acquisition and defence of a territory are critical for the fitness of an individual. Extensive evidence suggests that androgens (e.g. testosterone) are involved in the modulation of territorial behaviour in male vertebrates. Short-term increase of androgen following a territorial encounter appears to favour the outcome of a challenge. The "Challenge Hypothesis" proposed by Wingfield and colleagues outlines the existence of a positive feedback relationship between androgen and social challenges (e.g. territorial intrusions) in male vertebrates. Here we tested the challenge hypothesis in the highly territorial poison frog, Allobates femoralis, in its natural habitat by exposing males to simulated territorial intrusions in form of acoustic playbacks. We quantified repeatedly androgen concentrations of individual males via a non-invasive water-borne sampling approach. Our results show that A. femoralis males exhibited a positive behavioural and androgenic response after being confronted to simulated territorial intrusions, providing support for the Challenge Hypothesis in a territorial frog.

animal behavior and cognition↗