Multiyear Time-Shift Study of Bacteria and Phage Dynamics in the Phyllosphere.

AbstractCoevolution shapes diversity within and among populations but is difficult to study directly. Time-shift experiments, where individuals from one point in time are experimentally challenged against individuals from past, contemporary, and/or future time points, are a powerful tool to measure coevolution. This approach has proven useful both in directly measuring coevolutionary change and in distinguishing among coevolutionary models. However, these data are only as informative as the time window over which they were collected, and inference from shorter coevolutionary windows might conflict with those from longer time periods. Previous time-shift experiments from natural microbial communities of horse chestnut tree leaves uncovered an apparent asymmetry, whereby bacterial hosts were more resistant to bacteriophages from all earlier points in the growing season, while phages were most infective to hosts from only the recent past. Here, we extend the time window over which these infectivity and resistance ranges are observed across years and confirm that the previously observed asymmetry holds over longer timescales. These data suggest that existing coevolutionary theory should be revised to include the possibility of differing models for hosts and their parasites and examined for how such asymmetries might reshape the predicted outcomes of coevolution.

Pathology and reproductive health of queen conch (Lobatus gigas) in St. Kitts.

Queen conch, Lobatus gigas, are one of the largest commercial fisheries in the Caribbean and are severely depleted due to overharvesting. Dwindling and fragmented populations are at high risk to stochastic events such as disease epidemics; however, there is a paucity of literature regarding queen conch disease. A histopathological survey was conducted to assess the disease status of St. Kitts' queen conch populations, and contribute to the little information known about L. gigas pathology. Using a standard dissection and sampling protocol, pathology status was assessed in 61 L. gigas sampled opportunistically from fishermen in St. Kitts from October 2015 to November 2016. Pathology was observed in 13.1% (8/61) of the study population, mostly comprising internal parasitism (n = 5), especially encysted metazoan parasites (likely digenean metacercaria), observed in the gill, mantle, digestive gland and large intestine. Parasitism appeared incidental, having little impact on the host's health and minimal host response to the infection. Additionally, aspects of L. gigas reproductive health were analyzed: reproductive season in St. Kitts was confirmed from May to September; lip thickness is suggested as a better regulation measure for protecting juvenile populations compared to shell length; and variation in gonad color is found to be an unreliable predictor of reproductive activity. We conclude that disease appears to be uncommon in fisherman-caught L. gigas from St. Kitts. Pathologies observed elsewhere, including imposex and apicomplexan infection of the digestive gland, could not be substantiated in the study population. The cryptic nature of sick gastropods, as well as high predation rate and selection pressure for diseased queen conch may yield underrepresentation of pathology in such surveys. Future disease surveys could benefit from targeting stunted individuals, those showing unusual behavior, or those grown in an aquaculture environment.

Digestive gland inclusion bodies in queen conch (Lobatus gigas) are non-parasitic.

Unusual inclusion bodies occur within the epithelial cells of the digestive gland of queen conch, Lobatus gigas, and have previously been described as apicomplexan parasites. The aim of this study was to investigate the parasitic features of these inclusion bodies in queen conch. L. gigas from St. Kitts (Caribbean Sea) consistently (100% of n = 61) showed large numbers of ovoid to tri-bulbous dark brown inclusion bodies (15 × 30 µm) within vacuolar cells. Histochemical stains demonstrated iron, melanin, and glycoprotein and/or mucopolysaccharide within the inclusion bodies. Microscopic features indicative of a host response to injury were lacking in every case, as were consistent morphological forms to indicate distinct parasitic stages. Transmission electron microscopy failed to reveal cellular organelles of parasitic organisms and DNA extractions of purified inclusion bodies did not yield sufficient concentrations for successful PCR amplification. Scanning electron microscopy with energy dispersive X-ray analysis revealed a number of elements, particularly iron, within the inclusion bodies. We conclude that the inclusion bodies are not an infectious agent, and hypothesize that they represent a storage form for iron, and potentially other elements, within a protein matrix. Similar structures have been described in the digestive glands of other invertebrates, including prosobranchs.

The Queen Conch (Lobatus gigas) Proteome: A Valuable Tool for Biological Studies in Marine Gastropods.

Queen conch (Lobatus gigas) is a marine gastropod endemic to the Caribbean. This species is a cultural symbol, being a significant local food source and the second largest commercial fishery in the region. However, over-exploitation and natural habitat degradation have exerted high survival pressure on this species. This work aims to provide novel proteomic data to highlight the metabolism of the species and to provide an important tool for the understanding of queen conch biology and physiology. Herein, we profiled the whole proteome from 3 organs (gills, digestive gland and muscle) of L. gigas combining gel-free and gel-based techniques. Overall 420 clusters of proteins were identified corresponding to the minimum identification requirement of protein sequence redundancy. Gene ontology and KEGG analysis highlighted 59 metabolic pathways between identified proteins. The most relevant routes according to the number of sequences found per pathway were purine and thiamine metabolism, closely related to nucleotide and carbohydrate metabolism. We also emphasize the high number of proteins associated to the biosynthesis of antibiotics (93 proteins and a total of 28 enzymes), which were among the top-twenty pathways identified by KEGG analysis. The proteomics approach allowed the identification and description of putative markers of oxidative stress, xenobiotic metabolism, heat shock response and respiratory chain for the first time in the species, which could be extremely useful in future investigations for diagnosing and monitoring L. gigas population health.

Artificial nighttime light changes aphid-parasitoid population dynamics.

Artificial light at night (ALAN) is recognized as a widespread and increasingly important anthropogenic environmental pressure on wild species and their interactions. Understanding of how these impacts translate into changes in population dynamics of communities with multiple trophic levels is, however, severely lacking. In an outdoor mesocosm experiment we tested the effect of ALAN on the population dynamics of a plant-aphid-parasitoid community with one plant species, three aphid species and their specialist parasitoids. The light treatment reduced the abundance of two aphid species by 20% over five generations, most likely as a consequence of bottom-up effects, with reductions in bean plant biomass being observed. For the aphid Megoura viciae this effect was reversed under autumn conditions with the light treatment promoting continuous reproduction through asexuals. All three parasitoid species were negatively affected by the light treatment, through reduced host numbers and we discuss induced possible behavioural changes. These results suggest that, in addition to direct impacts on species behaviour, the impacts of ALAN can cascade through food webs with potentially far reaching effects on the wider ecosystem.