Biology subjects

Mennerat, A.

Publications and source records attributed to Mennerat, A..

3 recordsLinked to original sources

bioRxiv2023

Methods for tagging an ectoparasite, the salmon louse Lepeophtheirus salmonis

AO_SCPCAPBSTRACTC_SCPCAPMonitoring individuals within populations is a cornerstone in evolutionary ecology, yet individual tracking of invertebrates and particularly parasitic organisms remains rare. To address this gap, we describe here a method for attaching radio frequency identification (RFID) tags to individual adult females of a marine ectoparasite, the salmon louse Lepeophtheirus salmonis. Comparing two alternative types of glue, we found that one of them (2-octyl cyanoacrylate, 2oc) gave a significantly higher tag retention rate than the other (ethyl 2-cyanoacrylate, e2c). This glue comparison test also resulted in a higher loss rate of adult ectoparasites from the population where tagging was done using 2oc, but this included males not tagged and thus could also suggest a mere tank effect. Corroborating this, a more extensive analysis using data collected over two years showed no significant difference in mortality after repeated exposure to the 2oc glue, nor did it show any significant effect of the tagging procedure on the reproduction of female salmon lice. The proportion of RFID-tagged individuals followed a negative exponential decline, with tag retention among the living female population generally high. The projected retention was found to be about 88% after 30 days or 80% after 60 days, although one of the four batches of glue used, purchased from a different supplier, appeared to give significantly lower tag retention and with greater initial loss (74% and 60% respectively). Overall, we find that RFID tagging is a simple and effective technology that enables documenting individual life histories for invertebrates of a suitable size, including marine and parasitic species, and that it can be used over long periods of study.

ecology↗

bioRxiv2023

Adaptive host responses to infection can resemble parasitic manipulation

Using a dynamic optimisation model for juvenile fish in stochastic food environments, we investigate optimal hormonal regulation, energy allocation and foraging behaviour of a growing host infected by a parasite that only incurs an energetic cost. We find it optimal for the infected host to have higher levels of orexin, growth- and thyroid hormones, resulting in higher activity levels, increased foraging, and faster growth. This growth strategy thus displays several of the fingerprints often associated with parasite manipulation: higher levels of metabolic hormones, faster growth, higher allocation to reserves (i.e. parasite-induced gigantism), higher risk taking and eventually higher predation rate. However, there is no route for manipulation in our model, so these changes reflect adaptive host compensatory responses. Interestingly, several of these changes also increase the fitness of the parasite. Our results call for caution when interpreting observations of gigantism or risky host behaviours as parasite manipulation without further testing.

evolutionary biology↗

bioRxiv2018

Parasite intensity is driven by temperature in a wild passerine bird

Increasing awareness that parasitism is an essential component of nearly all aspects of ecosystem functioning, as well as a driver of biodiversity, has led to rising interest in the consequences of climate change in terms of parasitism and disease spread. Yet empirical knowledge on the extent and ways in which climatic factors affect parasite prevalence and intensities remains scarce. In an 18-year, multi-site, correlative study we investigated the contributions of weather variables and other factors to spatio-temporal variation in infestation by blowfly parasitic larvae (Protocalliphora spp.) in nests of Corsican blue tits (Cyanistes caeruleus). We found that ambient temperature during the nestling stage is strongly and positively related to parasite load (number of parasites per chick), both across broods when controlling for year, and across years. In addition, annual mean parasite load also increased with minimal spring temperature, and decreased with increasing average temperature in the previous summer. There was no indication of a dependence of parasite dynamics on host dynamics in this system, likely due in part to the wide host range of blowflies that do not solely rely on blue tit hosts. This suggests a major effect of temperature during the blowfly life cycle, with potential implications for blowfly - host interactions across their geographical range as climate keeps warming up. Finally, given that ambient temperature increases throughout the breeding season and that blowflies negatively affect survival and recruitment of blue tits, these results also mean that parasites, along with caterpillar availability, can drive selection for breeding date in this system.

ecology↗