Host Size Research Articles

Transmission potential of human schistosomes can be driven by resource competition among snail intermediate hosts

Predicting and disrupting transmission of human parasites from wildlife hosts or vectors remains challenging because ecological interactions can influence their epidemiological traits. Human schistosomes, parasitic flatworms that cycle between freshwater snails and humans, typify this challenge. Human exposure risk, given water contact, is driven by the production of free-living cercariae by snail populations. Conventional epidemiological models and management focus on the density of infected snails under the assumption that all snails are equally infectious. However, individual-level experiments contradict this assumption, showing increased production of schistosome cercariae with greater access to food resources. We built bioenergetics theory to predict how resource competition among snails drives the temporal dynamics of transmission potential to humans and tested these predictions with experimental epidemics and demonstrated consistency with field observations. This resource-explicit approach predicted an intense pulse of transmission potential when snail populations grow from low densities, i.e., when per capita access to resources is greatest, due to the resource-dependence of cercarial production. The experiment confirmed this prediction, identifying a strong effect of infected host size and the biomass of competitors on per capita cercarial production. A field survey of 109 waterbodies also found that per capita cercarial production decreased as competitor biomass increased. Further quantification of snail densities, sizes, cercarial production, and resources in diverse transmission sites is needed to assess the epidemiological importance of resource competition and support snail-based disruption of schistosome transmission. More broadly, this work illustrates how resource competition can sever the correspondence between infectious host density and transmission potential.

Metazoan parasite community of Hoplias malabaricus (Characiformes, Erythrinidae) in a stream of Caatinga domain, Brazil.

We purpose to describe and characterize the structure of the parasitic community of H. malabaricus in a stream from Caatinga domain, Ceará state, Brazil. A total of 42 specimens of H. malabaricus have been collected between December 2018 and August 2019, in which, 34 specimens were parasitized by at least one parasite. A total of 1,872 parasites were recovered, of which, 157 were Urocleidoides cuiabai (prevalence = 50%), 268 Urocleidodes brasiliensis (prevalence = 71.43%), 98 Dactylogyridae gen. sp. (prevalence = 14.29%), 401 Diplostomidae gen. sp. (prevalence = 4.76%), 183 Spiroxys sp. (prevalence = 42.86%) and 765 Pindapixara tarira (prevalence = 9.52%). The respective parasite species of H. malabaricus showed a pattern of overdispersion (or aggregation) typical of the parasitehost systems, corroborating with previous studies of parasitic communities of freshwater fish in Brazil. A positive and significant correlation between the host size and abundance of U. brasiliensis was verified. The ontogeny of fish can influence the parasitic load, some larger hosts tend to host larger quantities of parasites. The parasitic levels can vary with the host sex due to the differences in the ecological and physiological interactions between male and female. However, the host sex did not show influences in the prevalence and parasitic burden. All parasite taxa in this study have not yet been reported in the Carás stream, Caatinga domain. This finding extends the geographical distribution of this parasite species, furthermore, contributing to the knowledge of the biodiversity of fish parasites in the Neotropical region.

Co-infesting symbionts on a threatened marine host: evaluating correlations between an introduced parasitic isopod and a native symbiotic clam

In marine ecosystems, increased global-scale transportation creates opportunities for rapid introduction of invasive parasitic species that, in some cases, result in dramatic shifts within the native communities. A lack of detailed knowledge regarding the ecology of invasive marine parasites hinders our ability to develop effective conservation strategies and avoid unforeseen ecological consequences. We examined co-infestation patterns of a highly pathogenic, introduced parasitic isopod (Orthione griffenis) and a native symbiotic clam (Neaeromya rugifera) on the North American native blue mud shrimp Upogebia pugettensis. Our comparisons included infestations of O. griffenis and N. rugifera among 447 U. pugettensis hosts over 3 study years and were designed to statistically assess whether the 2 symbionts exhibited significant associations with one another. Our results indicate that infestations by the 2 symbiont species are positively correlated, such that the presence of one symbiont is a strong, positive predictor for the presence of the other. For both symbionts, host size is an important factor that drives the observed correlation. Host sex is also influential for O. griffenis. Interestingly, even after accounting for these host attributes, the infestations by the 2 symbionts continue to correlate positively, particularly among older (second-year and beyond) symbionts, highlighting the likely influence of additional host and environmental factors in driving the symbiont correlation post-settlement. We consider potential mechanisms, including differential energetic reserves and longevities between infested and co-infested hosts, in detail. These results offer insights into the ecological drivers of symbiont co-infestation, which have important implications for understanding host-parasite interactions and future conservation measures.

Crustacean and protozoan parasites of some cyprinid fish living in the Murat River (Bingöl-Türkiye), with new host records

Some Cyprinid fish species: Cyprinion macrostomum (Heckel, 1843), Capoeta umbla (Heckel, 1843), Chondrostoma regium (Heckel, 1843), and Squalius cephalus (Linnaeus, 1758) living naturally in the Murat River, were investigated for Protozoan and Crustacean parasite fauna and their distribution. Fish samples were collected from different stations between July 2017 - June 2019, examined in the Bingöl University Zoology Research Laboratory, and the data were explained with various variables. The normality test revealed that the data were not normally distributed (p< 0.05), as with large samples, so non-parametric tests explained the data. A total of 365 fish were examined, and 100 fish (27.4%) were infected with at least one Protozoan or Crustacean parasite. Four different parasite species were recorded on the examined fish, namely Ichthyophthirius multifiliis and Trichodina sp. belonging to the phylum Ciliophora (Protozoan), Ergasilus sieboldi, and Lamproglena pulchella belonging to the phylum Arthropoda (Crustacean). As a result of this study, for the first time, Protozoan and Crustacean parasites of different cyprinid fish were examined according to the host species, seasonal distribution, host size, and new host records were reported for three parasites.

Diversity and community ecology of metazoan parasites in Tetragonopterus argenteus Cuvier, 1816 (Characiformes, Characidae) from Jaguaribe River basin in Brazil.

The present study aims to inventory the metazoan parasites of Tetragonopterus argenteus from the Lima Campos weir, municipality of Icó, Ceará, Brazil and to analyze the influence of the host size and sex on the prevalence and parasitic abundance. A total of 359 metazoan parasites specimens were collected from 54 specimens of T. argenteus, presenting a mean intensity of 7.04 parasites/fish and prevalence of 94%. A richness of 10 parasite taxa were recorded, taxonomically classified into the following groups: Monogenea (n=1), Digenea (n=2) and Nematoda (n=7). The parasite community of T. argenteus was composed of helminth species with low prevalence, low mean intensity, low mean abundance, low dominance and low diversity, predominance of endoparasites of the phylum Nematoda. As for the importance value, six species were considered secondary and showed an aggregated dispersion pattern. The host size influenced significantly the abundance of Creptrotrema sp. and the prevalence of Procamallanus (Spirocamallanus) hilarii. The results present new reports of parasites have been recorded for this host, thus expanding the ecological interactions between parasites and Characiformes fish and contributing to the knowledge of the freshwater biodiversity from Brazilian Caatinga domain.

Ecology and diversity of metazoan parasites infecting Geophagus altifrons (Cichliformes: Cichlidae) from the Amazon River system in northern Brazil.

The aim of this study was to investigate the ecology and diversity of community and infracommunities of metazoan parasites Geophagus altifrons (Heckel, 1840) in Rio Jari, in the state of Amapá, in the eastern Amazon region. From the total of 31 fish examined, 90.3% were parasitized by one or more species, collecting a total number of 806 parasites. The parasites species identified were: Sciadicleithrum geophagi, Posthodiplostomum sp., Procamallanus (Spirocamallanus) inopinatus, Raphidascaris (Sprentacaris) sp., Genarchella genarchella, Gorytocephalus spectabilis and Ergasilus xinguensis. Most of the parasites showed an aggregate dispersion pattern. Brillouin diversity index, uniformity and species richness of parasites were low. The component community of parasites was constituted by ectoparasites and endoparasites, but with a predominance of ectoparasites. The body size of hosts had a low effect on the parasites infracommunities. This first eco-epidemiological study for G. altifrons reports these parasites in a host, for the first time, with the exception of S. geophagi and E. xinguensis.

Prevalence and Spatial Distribution of Ectoparasites in Wallago attu of River Penna, YSR District, Andhra Pradesh, India

An ectoparasitic survey on fish Wallago attu (n = 95) of river Penna, YSR district, Andhra Pradesh (India) was executed from August, 2017 to February, 2018. A total of 3202 parasites belonging three ectoparasitic groups viz., three monogeneans - Thaparocleidus indicus, thaparocleidus wallagonius, Mizelleus indicus, one copepod - Ergasilus malnadensis, and one isopod - Alitropus typus were detected from the gills of the examined hosts. Their spatial distributions on the host gills were reported. Only E. malnadensis, T. wallagonius and T. indicus showed aggregate distribution while the remaining two species, M. indicus and A. typus showed random distribution. Only, A. typus, T. wallagonius and T. indicus showed positive and statistically significant correlation with the condition factor. Location wise ectoparasite analysis revealed the higher infestation rates in site-II Somasila backwaters, Vontimitta compared to site-I Chennur. Spatial distribution studies revealed that there is no significant preference for the sides of the host fish. Both the sides of gill arch were equally infected. However, they showed preference within the gill arches. Monogeneans preferred gill arches II, III and IV, whereas copepods and isopods preferred gill arches I and II. There was meagre effect of host size and host sex on the ectoparasitic infection. These types of spatial distribution studies give an accurate location of the parasites to apply the eradication measures and eradicate them efficiently in fish aquaculture.

Epibiotic Communities of Common Crab Species in the Coastal Barents Sea: Biodiversity and Infestation Patterns

Crabs are important ecosystem engineers in marine habitats worldwide. Based on long-term data, we analyzed the species composition and infestation indices of epibionts and symbionts colonizing the great spider crab, Hyas araneus, and two lithodid crabs—the northern stone crab, Lithodes maja, and the red king crab, Paralithodes camtschaticus—in the coastal zone of the Barents Sea. The epibiotic communities found on great spider crabs were closer to northern stone crabs (33%) compared to red king crabs (25%). The prevalence of mobile symbionts (amphipods, Ischyrocerus, and polychaetes, Harmothoe) and common epibionts, such as barnacles and hydrozoans, was low on great spider crabs and high on the body and in the gills of lithodid crabs. Epiphytes were abundant on great spider crabs but not present on both species of lithodid crabs. Egg symbionts found on H. araneus and P. camtschaticus do not affect their local populations. Differences in the fouling communities found on the three crab species are associated with host size range, surface properties of their carapaces, and behavior patterns.

Directional changes over time in the species composition of tropical vascular epiphyte assemblages

Abstract Understanding the degree to which deterministic and stochastic processes drive community assembly is an ongoing focus of research in community ecology. This effort is strongly biased towards ground‐rooted plants, resulting in a limited understanding of communities of other life‐forms, such as structurally dependent plants. Vascular epiphytes are sessile organisms growing non‐parasitically on three‐dimensional dynamic patches, their host plants. Since negative biotic interactions are thought to play a minor role in vascular epiphyte assembly, in some forests, epiphytes are fascinating model organisms to understand the prevalence of environmental filtering in shaping community assembly. We assessed the contribution of deterministic processes on the temporal dynamics of vascular epiphyte assemblages by tracking the direction of changes in composition, species richness and abundance in time at different ecological and spatial scales. We made use of a globally unique dataset from a lowland forest in Panama. We predict that if niche‐based mechanisms dominate, (a) temporal changes will be directional and (b) differences in the species composition of epiphyte assemblages will be primarily related to host plant characteristics and, to a lesser degree, to the distance between host trees. We show that temporal changes in vascular epiphyte assemblages were directional at different ecological scales, such as the forest patch, host species or individual tree assemblages. Epiphyte assemblages on host trees became more similar in their composition over time than expected by chance, and these changes were not due to homogenisation. While host characteristics were related to these directional changes, host structure rather than host identity was more strongly related to variation in assemblage dissimilarity, while spatial distance among trees was of minor importance. The observed directionality was primarily due to environmental filtering. This study provides the first evidence that niche‐based mechanisms dominate the dynamics of vascular epiphyte assemblages. Analysing temporal patterns of vascular epiphyte assemblages is a first important step towards understanding the relative importance of deterministic processes for diversity maintenance of one of the most diverse plant groups in the tropics. Synthesis. Directionality in the temporal changes of epiphyte assemblages suggests that niche‐based mechanisms dominate these temporal changes. Host size over host identity is the most important environmental filter for epiphyte assemblages establishment.

Trophic interactions of vampire catfishes (Siluriformes: Vandelliinae) revealed by metabarcoding analysis of stomach contents

Abstract The trichomycterid catfishes of the subfamily Vandelliinae, the candirus, are parasite fishes that feed on blood. Therefore, the trophic interactions and dynamics of food webs in aquatic systems involving these catfishes cannot be determined through visual analysis of stomach contents, and the parasite–host interactions in this group of fishes are mostly unknown, except for a few anecdotal or experimental observations. We used DNA analysis of stomach contents of these fluid‐feeding fishes to identify hosts and study the ecological interactions of the haematophagous species Paravandellia oxyptera. Specifically, we used sequences of the cytochrome oxidase I gene collected from the gut contents of the catfish and compared them to data from GenBank to identify the host species. Our analysis indicated that examined specimens of Paravandellia oxyptera were exclusively fish parasites, and we identified genetic markers from eight host species from five families and three orders based on stomach contents. Paravandellia oxyptera does not exhibit host specificity. Unlike mucophagous trichomycterids, host species of haematophagous P. oxyptera belong to different trophic levels, showing a wide spectrum of interactions in the food web. A comparison of the host species with the accompanying fauna collected during sampling allowed an association between host preference and host size. Barcode analysis of stomach contents further produced a secondary source of information on the diversity of fish in the study area. This is the first study to identify host species of haematophagous parasitic fishes through the analysis of gut contents, demonstrating that specimens obtained in natural environments show much larger spectra of ecological interactions than previously reported from anecdotal or laboratory observations. This research is of broad interest, and exemplifies how DNA barcoding analysis of stomach contents provides new and relevant information on parasite/host interactions, with results not obtained by traditional methods of stomach content analysis.

Intense single-band red upconversion luminescence of Er3+/Yb3+ codoped BiOCl nanocrystals via a facile solvothermal strategy

Lanthanide doped BiOCl phosphors have recently emerged as a new type of upconversion (UC) host material due to their distinct crystal structure and tailorable UC emissions. However, the modulated single-band red UC luminescence through host size manipulation has not been well explored. In this work, we reported a facile solvothermal strategy to obtain the single-band red UC emission in BiOCl: Yb3+/Er3+ nanocrystals. It shows that just by changing the ethanol amount in the mixed solvent, the intense and pure red UC luminescence of Er3+ ion can be achieved at the same time. The possible reason for the single-band red UC emission and the dependence of UC luminescence intensity on the nanosheet size are proposed and discussed. The results of this work can provide an effective route to control the UC emission of Ln3+ doped layered materials, which might be widely applied in the areas of color displays and biological imaging.

Prevalence of Cymothoidae (Isopoda) Infestation in Bigeye Scad (Selar crumenophtalmus) from Batangas, Philippines

Cymothoid isopod research is relatively scarce in the Philippines, despite the local economic significance of bigeye scad as an inexpensive source of protein and other nutrients. Isopod parasitism has also been shown to have detrimental effects on their fish hosts. The current study aimed to define the host-parasite relationship between cymothoid isopod and bigeye scad by determining cymothoid isopod prevalence, intensity, and host-parasite length correlations in bigeye scad (Selar crumenophthalmus) hosts sourced from Batangas, Philippines. Fish samples were sampled from the Tagaytay City Market in Cavite, which sources fish directly from Batangas. Fish samples were immediately measured and inspected for isopods in the branchial and buccal cavities. Isopods found were extracted, measured, and preserved in ethanol for identification. The isopods were identified as cymothoid isopods and consisted mostly of Norileca indica specimens and one Glossobius impressus. Prevalence and mean intensity of cymothoid isopod infections in bigeye scad were 30% and 1.6, respectively. A possible correlation between isopod size and host size was speculated for non-ovigerous female isopods, but data for male and ovigerous female isopod specimens were inconclusive. The host-parasite size relationships between bigeye scad and isopods are less likely based on body size of either the host or the parasite and are more likely based on other factors such as host cavity size.

A molecular and ecological study of Grillotia (Cestoda: Trypanorhyncha) larval infection in small to mid-sized benthonic sharks in the Gulf of Naples, Mediterranean Sea.

AimTrypanorhyncha cestodes comprise a wide range of heteroxenous parasites infecting elasmobranchs as definitive hosts. Limited data exist on the larval infection of these cestodes and the role of intermediate and paratenic hosts in the life cycle of these parasites. We investigated the factors that determine the occurrence and the level of infection of Grillotia plerocerci in the skeletal muscles of various benthonic sharks and analyzed the parasites through an integrative taxonomic approach.LocationMediterranean Sea.MethodsSharks obtained as bycatch of commercial trawling activities (i.e., Etmopterus spinax, Galeus melastomus, and Scyliorhinus canicula) were used in this study. Data from a limited number of Dalatias licha and Scyliorhinus stellaris were also included. Grillotia plerocerci were molecularly characterized using the partial 28S large subunit rDNA. Boosted regression trees were used to model the relationship between the abundance of infection with both morphological and physiological predictors in each host.ResultsPlerocerci of Grillotia were detected in all shark species except S. stellaris. Host species significantly differed in terms of parasite abundance, with the highest and lowest prevalence and abundance of infection detected in G. melastomus and E. spinax, respectively. The relative influence of the traits involved in explaining the parasite abundance was related to the host size in G. melastomus, while both morphology‐ and physiology‐related traits explained the patterns observed in E. spinax and S. canicula. The 28S rDNA sequences shared an identity of ∼99.40% with a Grillotia species previously found in the Mediterranean Sea. At intraspecific level, two different genotypes were found. A first type was retrieved only from D. licha, whereas a second type was found in G. melastomus, E. spinax, and S. canicula.Main conclusionsPresent results suggest that the two genotypes could be involved in different consumer‐resource systems and confirm most of the examined shark species as transport hosts of Grillotia species for unknown larger top predators.

Seasonal dynamics of population and age composition of the trematode Gynaecotyla adunca larvae (Linton, 1905) Yamaguti, 1939 in the Black Sea

The purpose of the research is analyzing the seasonal dynamics for the number and the hemipopulation structure of the trematode Gynaecotyla adunca larvae in shrimps of the genus Palaemon Weber, 1795 and determining the dependence of their infection with the metacercariae G. adunca on the host size and the season of the year in the water area of Sevastopol.Materials and methods. Samples of aquatic organisms were collected monthly during 2012 in two different biotopes, the estuary of the Chernaya River and the Kazachya Bay. We examined a total of 2,445 specimens of the Hydrobia acuta mollusk, 200 specimens of the Palaemon elegans shrimp in the estuary of the Chernaya River, and 2,248 specimens of the H. acuta mollusks and 64 specimens of P. adsepsus in the water area of Kazachya Bay. Shrimps were caught with a 1 × 0.4 m seine with a 6–8 mm mesh. The mollusks were collected with a hand grab sampler with a sampling area of 0.04 m2. The mollusks and shrimps were classified in accordance with the World Register of Marine Species. All mollusk and shrimp tissues were examined by the compression method under an MBS-10 binocular microscope. Descriptive statistics was calculated using Statistica 6 for Windows.Results and discussion. We have found that the parthenita G. adunca is characterized by asynchronous emergence of secondary sporocyst that contain cercariae, while the metacercariae G. adunca hemipopulation is characterized by an overdispersed distribution, which indirectly indicates a low density of the host population and its constant migration. We analyzed seasonal dynamics of the found microfallid larvae population. The metacercariae G. adunca are characterized by one peak of infection with trematodes in summer.

Biotic and abiotic drivers affect parasite richness, prevalence and abundance in Mytilus galloprovincialis along the Northern Adriatic Sea.

Although it is generally known that a combination of abiotic and biotic drivers shapes the distribution and abundance of parasites, our understanding of the interplay of these factors remains to be assessed for most marine host species. The present field survey investigated spatial patterns of richness, prevalence and abundance of parasites in Mytilus galloprovincialis along the coast of the northern Adriatic Sea. Herein, the relationships between biotic (host size, density and local parasite richness of mussel population) and abiotic (eutrophication and salinity) drivers and parasite richness of mussel individuals, prevalence and abundance were analysed. Local parasite richness was the most relevant factor driving parasite species richness in mussel individuals. Prevalence was mainly driven by eutrophication levels in three out of four parasite species analysed. Similarly, abundance was driven mainly by eutrophication in two parasite species. Mussel size, density and salinity had only minor contributions to the best fitting models. This study highlights that the influence of abiotic and biotic drivers on parasite infections in mussels can be differentially conveyed, depending on the infection measure applied, i.e. parasite richness, prevalence or abundance. Furthermore, it stresses the importance of eutrophication as a major factor influencing parasite prevalence and abundance in mussels in the Adriatic Sea.

Plasticity of body growth and development in two cosmopolitan pupal parasitoids

Pachycrepoideus vindemiae and Trichopria drosophilae are cosmopolitan pupal parasitoids of Drosophilidae that attack the invasive Drosophila suzukii. This study investigated one aspect of their plasticity – host acceptance and offspring fitness on 25 Drosophila species in a phylogenetic framework. Each parasitoid’s key biological and ecological traits were compared among the different host species. Results demonstrate that both parasitoid species successfully parasitized and developed from all tested host species. Although the parasitoids’ efficiency and offspring fitness varied among host species, effects on life-history characteristics or ecological traits appeared to be unrelated to the phylogenetic position of tested host species. Both parasitoids benefited from attacking larger hosts, with body size of emerging progeny positively correlated to host size and an increased fecundity (mature egg load) of female wasps. Achieving larger body size came at no significant costs in immature development time. Results show remarkable levels of plasticity in the parasitoids’ body growth and development. Body size plasticity in T. drosophilae and P. vindemiae could improve biological control by increasing variation in parasitoid body sizes. Large size may not be advantageous under all conditions, however, and the parasitoids’ ecoservice impacts will be influenced not only by their plasticity to hosts but by environmental limitations such as temperature tolerances, habitat location, and host searching behaviors.

Infection prevalence and density of a pathogenic trematode parasite decrease with stream order along a river continuum

AbstractIn lotic ecosystems, the River Continuum Concept (RCC) provides a framework for understanding changes in environmental factors and free‐living communities, yet how parasite populations shift along river continua remains less clear. We quantified infections by a pathogenic trematode parasite (Nanophyetus salmincola) in >14,000 host snails across 130 stream reaches spanning 165 km in the Willamette River Basin in western Oregon, USA. Environmental factors—including flow volume, temperature, benthic algae, canopy cover, woody debris, and land cover—changed predictably with stream order, consistent with the RCC. From first‐ to eighth‐order reaches, infection prevalence decreased by ˜42‐fold and infected snail density, a measure of disease risk to fish hosts, decreased ˜3‐fold. Infected snail density, but not prevalence, was positively associated with snail biomass density, and individual infection probability increased strongly with host size. Shifts in snail population characteristics across stream orders, however, did not explain the observed changes in N. salmincola populations, suggesting that environmental variables and corresponding changes in non‐snail hosts explain the downstream decrease in infections. Our findings show predictable spatial variation in disease risk to vertebrate hosts from N. salmincola and indicate the RCC can help explain shifts in parasite populations in lotic ecosystems.

Hidden structural heterogeneity enhances marine hotspots\u2019 biodiversity

Studies in terrestrial and shallow-water ecosystems have unravelled the key role of interspecific interactions in enhancing biodiversity, but important knowledge gaps persist for the deep sea. Cold-water coral reefs are hotspots of biodiversity, but the role of interspecific interactions and “habitat cascades” (i.e. positive effects on focal organisms mediated by biogenic habitat formation) in shaping their biodiversity is unknown. Associations between macrofaunal hosts and epifauna were examined in 47 stations at the Mingulay Reef Complex (northeast Atlantic). In total, 101 (group level) and 340 (species level) unique types of facultative associations formed by 43 hosts and 39 epifaunal species were found. Molluscs and empty polychaete tubes had higher values for the type and number of host-epifaunal associations, the Shannon–Wiener (H) and Margalef (d) indices of the epifauna than the rest of the taxonomic groups (p < 0.05). Hosts’ body size, orientation, surface smoothness, and growth form explained a significant amount of variability (32.96%) in epifauna community composition. Epifaunal species richness (S), H and d were 27.4 (± 2.2%), 56.2 (± 2.8%) and 39.9 (± 2.3%) of the respective values for the total sessile communities living on coral framework. This is intriguing as coral framework is orders of magnitude larger than the size of macrofaunal hosts. It is suggested that bivalves, tunicates and empty polychaete tubes increase habitat heterogeneity and enhance biodiversity through “habitat cascades”, in a similar way that epiphytes do in tropical rainforests. Most macrofaunal habitat suppliers in the studied cold-water coral reef are calcified species and likely susceptible to ocean acidification. This indicates that the impacts of climate change on the total biodiversity, structure and health of cold-water coral reefs may potentially be more severe than previously thought.

Escaping the evolutionary trap: Can size-related contest advantage compensate for juvenile mortality disadvantage when parasitoids develop in unnatural invasive hosts?

The quality of hosts for a parasitoid wasp may be influenced by attributes such as host size or species, with high quality for successful development usually coincident with high quality for larger offspring. This is not always the case: for the Scelionid wasp Trissolcus basalis, oviposition in eggs of the Brown Marmorated Stink Bug, Halyomorpha halys, rather than of the normal host, the Southern Green Stink Bug, Nezara viridula, leads to lower offspring survival, but survivors can be unusually large. Adult female T. basalis engage in contests for host access. As larger contestants are typically favoured in contests between parasitoids, the larger size of surviving offspring may compensate for the mortality of others. We construct a general game-theoretic model to explore whether size advantage can sustain a maternal preference to utilize a more deadly host species. We find that size advantage alone is unlikely to sustain a shift in host preference, yet such an outcome is possible when size asymmetries act simultaneously with advantages in host possession (ownership effect). Halyomorpha halys is an invasive pest of major agro-economic importance in Europe and the Americas, and use of its eggs as hosts by native parasitoids such as T. basalis has been seen as an evolutionary trap due to their high developmental mortality. Our model suggests that the recently discovered effect of host choice on offspring size may provide an escape from the trap via effects on contest biology of T. basalis which could foster a more stable association with H. halys. An evolutionary shift in the reproductive value of H. halys could increase the efficiency of T. basalis as a biological control agent of this invasive stink bug pest.

Novel genomic approaches to study antagonistic coevolution between hosts and parasites.

Host-parasite coevolution is ubiquitous, shaping genetic and phenotypic diversity and the evolutionary trajectory of interacting species. With the advances of high throughput sequencing technologies applicable to model and non-model organisms alike, it is now feasible to study in greater detail (a) the genetic underpinnings of coevolution, (b) the speed and type of dynamics at coevolving loci, and (c) the genomic consequences of coevolution. This review focuses on three recently developed approaches that leverage information from host and parasite full genome data simultaneously to pinpoint coevolving loci and draw inference on the coevolutionary history. First, co-genome-wide association study (co-GWAS) methods allow pinpointing the loci underlying host-parasite interactions. These methods focus on detecting associations between genetic variants and the outcome of experimental infection tests or on correlations between genomes of naturally infected hosts and their infecting parasites. Second, extensions to population genomics methods can detect genes under coevolution and infer the coevolutionary history, such as fitness costs. Third, correlations between host and parasite population size in time are indicative of coevolution, and polymorphism levels across independent spatially distributed populations of hosts and parasites can reveal coevolutionary loci and infer coevolutionary history. We describe the principles of these three approaches and discuss their advantages and limitations based on coevolutionary theory. We present recommendations for their application to various host (prokaryotes, fungi, plants, and animals) and parasite (viruses, bacteria, fungi, and macroparasites) species. We conclude by pointing out methodological and theoretical gaps to be filled to extract maximum information from full genome data and thereby to shed light on the molecular underpinnings of coevolution.