Host–parasite coevolution may result in life-history changes in hosts that can limit the detrimental effects of parasitism. Fecundity compensation is one such life-history response, occurring when hosts increase their current reproductive output to make up for expected losses in future reproduction due to parasitic infection. However, the potential trade-offs between this increase in quantity and the quality of offspring have been relatively unexplored. This study uses the trematode, Schistosoma mansoni, and its snail intermediate host, Biomphalaria glabrata, to better understand how this host life-history response, fecundity compensation, impacts host reproduction. Measures of host reproductive output as well as offspring hatching success and survival were collected to assess the reproductive consequences of infection. Infected snails exhibited fecundity compensation by increasing the number of eggs laid and the overall probability of laying eggs compared to uninfected snails. Parental infection status did not play a significant role in hatching or offspring survival to maturity. Offspring from a later reproductive bout demonstrated a higher hatching success rate. Overall, the lack of an apparent trade-off between quantity and quality of offspring suggests that infected parental snails invest more resources towards reproduction not only to increase reproductive output, but also to maintain the fitness of their offspring, possibly at the expense of their own longevity.
Increased urbanization has resulted in community changes including alteration of predator communities. Little is known, however, about how such changes affect morphological anti-predator traits. Given the importance of coloration in predator avoidance, this trait in particular is expected to be susceptible to novel selective environments in urban areas. Here, we investigate the coloration pattern of a Neotropical anuran species, the túngara frog (Engystomops pustulosus), along an urbanization gradient. Túngara frogs have two distinct color patterns (unstriped and striped) which we found to occur at different frequencies along an urbanization gradient. Striped individuals increased in frequency with urbanization. To assess the strength of selection imposed by predators on the two color morphs, we deployed clay models of túngara frogs in forest and semi-urban populations. In addition, we examined microhabitat selection by individuals of the different morphs. We found higher predation rates associated with urbanization than forested areas. In particular, frogs from forested habitats had lower number of attacks by avian predators. Contrary to our predictions, however, predation rates were similar for both color morphs independent of urbanization. Also, coloration of the frogs did not affect their microhabitat preference. Overall, túngara frogs are more likely to have a striped coloration pattern in semi-urban areas where predation by birds is higher than in the forest. Our findings suggest that factors other than predation pressure shape the coloration pattern of urban frogs and emphasize the complex nature of effects that anthropogenic changes in habitat and predator communities may have on prey morphology.
The global increase in antibiotic use has led to contamination of freshwater environments occupied by parasites and their hosts. Despite the identified impacts of antibiotics on humans and wildlife, the effect of antibiotics on host-parasite life cycles is relatively unexplored. We utilize the trematode parasite Schistosoma mansoni, and its snail intermediate host Biomphalaria glabrata to explore the influence of an ecologically relevant antibiotic concentrations on the life history characteristics of both parasite and host. Our results demonstrate that antibiotics not only accelerate parasite development and have a positive effect on parasite reproduction, but also increase the likelihood of host egg laying, and delay parasite-induced host castration. Using a mathematical model, we suggest that these life history alterations associated with antibiotics are likely to increase parasite transmission and disease burden.
Predators and parasites are critical, interconnected members of the community and have the potential to shape host populations. Predators, in particular, can have direct and indirect impacts on disease dynamics. By removing hosts and their parasites, predators alter both host and parasite populations and ultimately shape disease transmission. Selective predation of infected hosts has received considerable attention as it is recognized to have important ecological implications. The occurrence and consequences of preferential consumption of uninfected hosts, however, has rarely been considered. Here, we synthesize current evidence suggesting this strategy of selectively predating uninfected individuals is likely more common than previously anticipated and address how including this predation strategy can change our understanding of the ecology and evolution of disease dynamics. Selective predation strategies are expected to differentially impact ecological dynamics and therefore, consideration of both strategies is required to fully understand the impact of predation on prey and host densities. In addition, given that different strategies of prey selectivity by predators change the fitness payoffs both for hosts and their parasites, we predict amplified coevolutionary rates under selective predation of infected hosts compared to uninfected hosts. Using recent work highlighting the critical role that predators play in disease dynamics, we provide insights into the potential mechanisms by which selective predation on healthy individuals can directly affect ecological outcomes and impact long-term host-parasite coevolution. We contrast the consequences of both scenarios of selective predation while identifying current gaps in the literature and future research directions.
The global increase in antibiotic use has led to contamination of freshwater environments. Despite the identified impacts of antibiotics on humans and wildlife, the effect of antibiotics on host–parasite life cycles in freshwater is relatively unexplored. In the current study, we utilize the trematode parasite Schistosoma mansoni, and its snail intermediate host, Biomphalaria glabrata, to investigate the influence of an ecologically relevant antibiotic concentration on the life history characteristics of both parasite and host. Our results demonstrate that antibiotics not only accelerate parasite development time, but also increase host reproduction and delay parasite‐induced host castration. Using a mathematical model, we suggest that life history alterations associated with antibiotics are likely to increase parasite transmission and disease burden. Our study suggests that antibiotic pollution could impact freshwater ecosystems by influencing host–parasite dynamics and potentially increase the burden of schistosomiasis in endemic regions.
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