Biology subjects

Giraudeau, M.

Publications and source records attributed to Giraudeau, M..

3 recordsLinked to original sources

bioRxiv2023

Life history and cancer in birds: clutch size predicts cancer

Cancer is a disease that affects nearly all multicellular life, including birds. However, little is known about what factors explain the variance in cancer prevalence among species. Litter size is positively correlated with cancer prevalence in managed species of mammals, and larger body size, but not incubation or nestling period, is linked to tumor prevalence in wild birds. Also, birds that produce more elaborate sexual traits are expected to have fewer resources for cancer defenses and thus higher cancer prevalence. In this study, we examined whether cancer prevalence is associated with a wide variety of life history traits (clutch size, incubation length, body mass, lifespan, and the extent of sexual dimorphism) across 108 species of managed birds in 25 different zoological facilities, sanctuaries, and veterinary clinics. We found that clutch size was positively correlated with cancer and neoplasia (both benign and malignant) prevalence, even after controlling for body mass. Cancer prevalence was not associated with incubation length, body mass, lifespan, or sexual dimorphism. The positive correlations of clutch size with cancer prevalence and neoplasia prevalence suggest that there may be life-history trade-offs between reproductive investment and somatic maintenance (in the form of cancer prevention mechanisms) in managed birds.

cancer biology↗

bioRxiv2020

Exercise training in a color-polymorphic lizard reveals differential effects of mating tactics and color morphs on telomere, body condition and growth dynamics

Alternative reproductive tactics (ARTs) are correlated suites of sexually selected traits that are likely to impose differential physiological costs on different individuals. While some level of activity might be beneficial, animals living in the wild are often working at the margins of their resources and performance limits. Individuals using ARTs may have divergent capacities for activity, and when pushed beyond their capacity, they may experience condition loss, oxidative stress, and molecular damage that must be repaired with limited resources. We used the Australian painted dragon lizard that exhibits color-polymorphims with corresponding alternative reproductive tactics (ARTs) as a model to experimentally test the effect of exercise on body condition, growth, reactive oxygen species (ROS), and telomere dynamics--a potential marker of stress and aging and a correlate of longevity. For most males, ROS tended to be lower with greater exercise; however, males with yellow throat patches--or bibs-- had higher ROS than non-bibbed males. At the highest level of exercise, bibbed males exhibited telomere loss, while non-bibbed males gained telomere length; the opposite pattern was observed in the no-exercise controls. Growth was positively related to food intake but negatively correlated with telomere length at the end of the experiment. Body condition was not related to food intake but was positively correlated with increases in telomere length. These results, along with our previous work, suggest that aggressive bibbed males suffer physiological costs that may reduce longevity.

evolutionary biology↗

bioRxiv2018

Evolution of host resistance and damage-limiting mechanisms to an emerging bacterial pathogen

Understanding how hosts minimise the cost of emerging infections has fundamental implications for epidemiological dynamics and the evolution of pathogen virulence. Despite this, few experimental studies conducted in natural populations have explicitly tested whether hosts evolve resistance, which prevents infections or reduces pathogen load through immune activation, or tolerance, which limits somatic damages without decreasing pathogen load. In addition, none have done so controlling for the virulence of the pathogen isolate used, despite critical effects on host responses to infection. Here, we conducted an experimental inoculation study to test whether eastern North American house finches (Haemorrhous mexicanus) have evolved resistance or tolerance to their emerging bacterial pathogen, Mycoplasma gallisepticum, using 55 distinct isolates of varying virulence. First, we show that peak pathogen loads, which occurred around 8 days post-inoculation, did not differ between experimentally inoculated finches from disease-exposed (eastern) versus unexposed (western) population. However, pathogen loads subsequently decreased faster and to a greater extent in finches from exposed populations, indicating that they were able to clear the infection through adaptive immune processes. Second, we found no between-population difference in the regression of clinical symptom severity on pathogen load; if tolerance had evolved then the slope of this regression is predicted to be shallower (less negative) in the exposed population. However, finches from exposed populations displayed lower symptom severity for a given pathogen load, suggesting that damage-limitation mechanisms have accompanied the evolution of immune clearance. These observations show that resistance and damage-limitation mechanisms - including, but not limited to the standard conceptualisation of tolerance - should not be seen as mutually exclusive. Nevertheless, we propose that host resistance is especially likely to evolve in response to pathogens such as M. gallisepticum that require virulence for successful infection and transmission.

evolutionary biology↗