Biology subjects

Ruiz-Raya, F.

Publications and source records attributed to Ruiz-Raya, F..

5 recordsLinked to original sources

bioRxiv2025

Seasonal decline in mitochondrial plasticity in the three-spined stickleback

Mitochondrial plasticity enables ectothermic animals to maintain performance under changing thermal conditions, but whether this ability declines through adulthood is unknown. We explored changes in mitochondrial plasticity in the three-spined stickleback (Gasterosteus aculeatus), a temperate fish that in many populations has a single breeding season over which it produces multiple clutches and then dies. Wild-caught fish were exposed to one of three thermal regimes: remaining at 12 {degrees}C, switching to constant warm (21 {degrees}C) or diel cycling (12-21 {degrees}C) for three weeks at either the beginning or end of the season. We quantified both phosphorylating and non-ATP-producing (OXPHOS and LEAK) respiration in isolated muscle mitochondria, and oxidative control efficiency (OxCE). Early in the breeding season, young fish responded to elevated temperatures by adjusting both their capacity for ATP production and non-ATP-production respiration, but this mitochondrial plasticity declined over the season. OxCE was unaffected by time of season or temperature treatment. Changing body condition was unrelated to mitochondrial function. Our findings indicate that mitochondrial plasticity declines across adult life, potentially limiting thermal resilience in older individuals, the first time this has been reported in an ectotherm. This highlights the need to account for age-related physiological changes in capacity when predicting species responses to environmental change.

evolutionary biology↗

bioRxiv2024

Asymptomatic infection and antibody prevalence to co-occurring avian influenza viruses vary substantially between sympatric seabird species following H5N1 outbreaks

Emerging infectious diseases are of major concern to animal and human health. Recent emergence of high pathogenicity avian influenza virus (HPAIV) (H5N1 clade 2.3.4.4b) led to substantial global mortality across a range of host species. Co-occurring species showed marked differences in mortality, generating an urgent need for better epidemiological understanding within affected populations. We therefore tested for antibodies, indicative of previous exposure and recovery, and for active viral infection in apparently healthy individuals (n=350) across five co-occurring seabird species on the Isle of May, Scotland, during 2023, following H5N1 HPAIV associated mortality in the preceding summer. Antibody prevalence to AIV subtypes varied substantially between species, ranging from 1.1% in European shags (Gulosus aristotelis) (to H5) to 78.7% in black-legged kittiwakes (Rissa tridactyla) (to H16 or both H13 and H16), and between 31-41% for three auk species (H5, H16 or both). At least 20.4% of auks had antibodies to an as yet unidentified subtype, suggesting further subtypes circulating in the population. We found low levels of active, but asymptomatic, AIV infection in individuals (1.6-4.5%), but excluded this as H5N1. Our results emphasise the importance of testing healthy individuals to understand the prevalence of co-circulating AIV subtypes in wild populations, and the potential for future reassortment events which could alter virus behaviour and impact.

ecology↗

bioRxiv2022

Physiological stress responses to non-mimetic model brood parasite eggs: leukocyte profiles and heat-shock protein Hsp70 levels

Obligate avian brood parasites lay their eggs in the nest of other bird species (hosts). Brood parasitism often imposes severe fitness costs on hosts, which selects for the evolution of effective anti-parasitic defences, such as recognition and rejection of brood parasite eggs. Glucocorticoids have been recently found to mediate host physiological and behavioural adjustments in response to brood parasite eggs; however, it remains unclear whether brood parasitism triggers a general response involving multiple physiological elements. In this study, we experimentally investigated whether a salient brood parasitic stimulus (the presence of a non-mimetic model egg in the nest) causes physiological adjustments in adult Eurasian blackbirds (Turdus merula) at immune (leukocyte profiles) and cellular (heat-shock protein Hsp70 synthesis) level. Also, we explored whether these physiological changes are mediated by variations in corticosterone levels. We found that experimental brood parasitism caused an increase in heterophils and a decrease in lymphocytes, leading to higher H/L ratios in parasitized birds. Nevertheless, we did not find trade-offs between immune function and corticosterone levels. Hsp70 synthesis was not affected by our experimental manipulation. Our findings provide evidence that brood parasite eggs trigger a general stress response in egg-rejecter hosts, including changes in cellular immune profiles.

animal behavior and cognition↗

bioRxiv2020

Parental feeding preferences rather than sibling competition determine the death of smaller nestlings in asynchronous broods

Hatching asynchrony is a reproductive tactic that, through the creation of competitive hierarchies among offspring, allows parents for a quick adjustment of brood size via the death of smaller nestlings. This strategy is considered to be adaptive in case of unpredictable and/or poor environments in which it would guarantee that at least larger nestlings will fledge. Brood reduction is the usual outcome in asynchronously hatched broods since first-hatched nestlings are larger and get a disproportionately larger share of the food delivered by parents, often leading the youngest nestling to starve to death soon after hatching. However, we still do not know the proximate mechanisms of such brood reduction. One possibility is that the smallest nestling is not fed because larger nestlings outcompete it, which implies that nestlings control resource allocation. Alternatively, parents might actively ignore the persistent begging from their smallest nestling, which would involve that parents control food allocation. To determine whether parents or nestlings ultimately induce brood reduction in this situation, we experimentally created asynchronous broods of Eurasian blackbird (Turdus merula) nestlings and quantified food allocation by parents in two different situations: when sibling competition was allowed and, alternatively, when competition was prevented by physically separating nestlings within the nests by using wooden barriers. Our results showed that experimentally introduced smaller nestlings received less food than their larger nestmates both when competition among nestlings was allowed and when it was prevented. When adult males and females are considered separately, males fed the smallest nestling less often regardless of whether sibling competition was allowed or not, but adult females showed no differences. We can conclude that the smallest nestling starves mainly because parents actively ignore its begging. The higher competitive ability of the larger nestlings seem to have little effect given that although the smallest nestling is fed at a higher rate when physical interactions are prevented by the wooden barrier than when not, this difference is not significant. These findings suggest that parents rather than nestlings have the main control over food allocation.

animal behavior and cognition↗

bioRxiv2020

Prolactin mediates behavioural rejection responses to avian brood parasitism

Even though adaptations resulting from co-evolutionary interactions between avian brood parasites and their hosts have been well studied, the hormonal mechanisms underlying behavioural host defences remain largely unexplored. Prolactin, the main hormone mediating avian parental behaviour, has been hypothesized to play a key role in the orchestration of host responses to brood parasitic eggs. Based on the positive association between plasma prolactin and parental attachment to eggs, decreasing levels of this hormone are expected to facilitate egg-rejection decisions in parasitized clutches. We tested this prediction by implanting Eurasian blackbirds (Turdus merula) females with an inhibitor of prolactin secretion, bromocriptine mesylate, to experimentally low their prolactin levels. We found that bromocriptine-treated females rejected mimetic model eggs at higher rates than placebo-treated individuals. To our knowledge, this is the first experimental evidence that host responses to brood parasitism are mediated by the primary endocrine pathway that orchestrates the expression of avian parental care.

animal behavior and cognition↗