Trojan horses in the marine realm: characterizing protistan parasite ecology in coastal waters

Protists are taxonomically and metabolically diverse drivers of energy and nutrient flow in the marine environment, with recent research suggesting significant roles in global carbon cycling throughout the water column. Top-down controls on planktonic protists include grazing and parasitism, processes that both contribute to nutrient transfer and biogeochemical cycling in the global ocean. Recent global surveys of eukaryotic small subunit ribosomal RNA molecular signatures have highlighted the fact that parasites belonging to the marine alveolate order Syndiniales are both abundant and ubiquitous in coastal and open ocean environments, suggesting a major role for this taxon in marine food webs. Two coastal sites, Saanich Inlet (Vancouver Island, BC) and Salt Pond (Falmouth, MA, USA) were selected as model ecosystems to examine the impacts of Syndinian parasitism on protist communities. Data presented in this thesis combines high-resolution sampling, water chemistry (including nutrients) analyses, molecular marker gene analyses, fluorescence in situ hybridization, and modeling to address key knowledge gaps regarding syndinian ecology. Information is presented on previously undescribed putative host taxa, the prevalence of syndinian parasites and infections on different hosts in coastal waters, and a framework for modeling host-parasite interactions based on field observations.

Ecology of Ticks (Ixodidae) on Cattle within Main Campus of the University of Abuja, Nigeria

A survey was conducted using standard parasitological procedures to determine the ecology of ticks on the cattle within the main campus of the University of Abuja, Nigeria. The tick specie identified were Amblyomma variegatum, Amblyomma hebraeum, 0rnithodorus moubata complex, Hyalomma truncatum, Hyalomma rufipies, Rhipicephalus decoloratus, Phipicephalus appendiculatus, and Boophilus microplus. Of the 100 cattle examined. 47(47%) of the tick examined was found on the male cow and 53(53%) were found on the female cow. In addition, 23(23%) of the observed tick are found on the leg, 20(20%) are found in the anus, 20(20%) are found on the udder, 14(14%) are found on the back while 23(23%) of the ticks are found in the ear. 31(31%) of the observed ticks were found on the bunaj specie, 24(24%) of the ticks on the Gudali, 24(24%) of the observed ticks on the Rahaji specie and 21(21%) on the wadara specie. Amblyomma hebraeum, Ornithodorus moubata Complex and Rhipicephalus dicoloratus were found more dominantly on Bunaj breed (42.9%, 55.6% and 42.9% respectively), Amblyomma variegatum and Phipicephalus appendiculatus was observed to be more dominant on Rahaji breed (infesting 33.3% and 66.7% respectively), Boophylus microplus and Hyalomma rufipe were found dominant on wadara (30% and 50% respectively). There is need to help establish baseline information on ticks ecology and occurrence in the study area which would consequently lead to increased public awareness especially to the herdsmen and in avoiding tick borne diseases, also to help in vector control formulation and to prevent the herdsmen of suffering from low productivity due to the presence of ticks, thereby leading to various weaknesses, diseases and sometimes death of the cattle. Owing to this, this study did not only identify the tick species infesting cattle but also examined the host-parasite ecology of ticks on cattle within the main campus of the University of Abuja, Nigeria.

Current Knowledge of Small Flukes (Digenea: Heterophyidae) from South America

Fish-borne heterophyid trematodes are known to have a zoonotic potential, since at least 30 species are able to infect humans worldwide, with a global infection of around 7 million people. In this paper, a ‘state-of-the-art’ review of the South American heterophyid species is provided, including classical and molecular taxonomy, parasite ecology, host-parasite interaction studies and a list of species and their hosts. There is still a lack of information on human infections in South America with undetected or unreported infections probably due to the information shortage and little attention by physicians to these small intestinal flukes. Molecular tools for specific diagnoses of South American heterophyid species are still to be defined. Additional new sequences of Pygidiopsis macrostomum, Ascocotyle pindoramensis and Ascocotyle longa from Brazil are also provided.

Ecto- and endoparasites of the King's skink (Egernia kingii) on Penguin Island

Wildlife species are often host to a diversity of parasites, but our knowledge of their diversity and ecology is extremely limited, especially for reptiles. Little is known about the host-parasite ecology of the Australian lizard, the King's skink (Egernia kingii). In spring of 2015, we carried out a field-based study of a population of King's skinks on Penguin Island (Western Australia). We documented five species of parasites, including two ectoparasitic mites (an undescribed laelapid mite and Mesolaelaps australiensis), an undescribed coccidia species, and two nematode species (Pharyngodon tiliquae and Capillaria sp.). The laelapid mite was the most abundant parasite, infesting 46.9% of the 113 captured lizards. This mite species increased in prevalence and abundance over the course of the study. Infection patterns of both mites varied with lizard life-stage; sub-adults were more commonly infested with laelapid mites than adults or juveniles, and sub-adults and adults were infested by more laelapid mites than juveniles. By contrast, adults had a higher prevalence of M. australiensis than juveniles or sub-adults. Among the gastrointestinal parasites, P. tiliquae was relatively common among the sampled lizards (35.3%). These results give new important information about reptiles as parasite hosts and what factors influence infection patterns.

Hooked on you: shape of attachment structures in cymothoid isopods reflects parasitic strategy

Background Parasite attachment structures are critical traits that influence effective host exploitation and survival. Morphology of attachment structures can reinforce host specificity and niche specialisation, or even enable host switching. Therefore, it is important to understand the determinants of variation in attachment structures. Cymothoid isopods are striking ectoparasites of fishes that include the infamous ‘tongue-biters.’ They are known to parasitise hosts in one of four qualitatively distinct anatomical regions. Here, we quantify variation in cymothoid attachment structures — hook-like appendages called dactyli — and test whether differences in dactylus shape are correlated with parasite mode (where they attach), allometry, or both, using multivariate ordinary least squares regression. We also assess the influence of shared ancestry on shape using a molecular phylogeny to weight our models using phylogenetic generalised least squares regression. Results We find clear differences in shape between externally-attaching and internally-attaching cymothoids but also between anterior and posterior dactyli across various species with the same attachment mode. Allometric effects are significant for anterior but not posterior dactyli. Mouth-attaching species show greater shape variability than gill- and mouth-attaching species. We find no evidence that there are clade-specific patterns of association between parasite mode and dactylus shape. Conclusions Parasite mode appears to be the main driver of attachment morphology. This likely reflects several components of parasite ecology including feeding and functional demands of attachment in different microhabitats. Geometric morphometric approaches to the quantification of shape variation of simple structures is an effective tool that provides new insights into the evolvability of parasite attachment.

On the mechanistic roots of an ecological law: parasite aggregation

Parasite aggregation, a recurring pattern in macroparasite infections, is considered one of the “laws” of parasite ecology. Few hosts have a large number of parasites while most hosts have a low number of parasites. Phenomenological models of host-parasite systems thus use the negative-binomial distribution. However, to infer the mechanisms of aggregation, a mechanistic model that does not make any a priori assumptions is essential. Here we formulate a mechanistic model of parasite aggregation in hosts without assuming a negative-binomial distribution. Our results show that a simple model of parasite accumulation still results in an aggregated pattern, as shown by the derived mean and variance of the parasite distribution. By incorporating the derived statistics in host-parasite interactions, we can predict how aggregation affects the population dynamics of the hosts and parasites through time. Thus, our results can directly be applied to observed data as well as can inform the designing of statistical sampling procedures. Overall, we have shown how a plausible mechanistic process can result in the often observed phenomenon of parasite aggregation occurring in numerous ecological scenarios, thus providing a basis for a “law” of ecology.

Linking Bioenergetics and Parasite Transmission Models Suggests Mismatch Between Snail Host Density and Production of Human Schistosomes

The consequences of parasite infection for individual hosts depend on key features of host–parasite ecology underpinning parasite growth and immune defense, such as age, sex, resource supply, and environmental stressors. Scaling these features and their underlying mechanisms from the individual host is challenging but necessary, as they shape parasite transmission at the population level. Translating individual-level mechanisms across scales could inherently improve the way we think about feedbacks among parasitism, the mechanisms driving transmission, and the consequences of human impact and disease control efforts. Here, we use individual-based models (IBMs) based on general metabolic theory, Dynamic Energy Budget (DEB) theory, to scale explicit life-history features of individual hosts, such as growth, reproduction, parasite production, and death, to parasite transmission at the population level over a range of resource supplies focusing on the major human parasite, Schistosoma mansoni, and its intermediate host snail, Biomphalaria glabrata. At the individual level, infected hosts produce fewer parasites at lower resources as competition increases. At the population level, our DEB–IBM predicts brief, but intense parasite peaks early during the host growth season when resources are abundant and infected hosts are few. The timing of these peaks challenges the status quo that high densities of infected hosts produce the highest parasite densities. As expected, high resource supply boosts parasite output, but parasite output also peaks at modest to high host background mortality rates, which parallels overcompensation in stage-structured models. Our combined results reveal the crucial role of individual-level physiology in identifying how environmental conditions, time of the year, and key feedbacks within host–parasite ecology interact to define periods of elevated risk. The testable forecasts from this physiologically-explicit epidemiological model can inform disease management to reduce human risk of schistosome infection.

A systematic review of parasites and micropredators of non-avian reptiles (Reptilia=Sauropsida) in Chile

Knowledge about the identity of parasites in vertebrates is relevant because of their influence on ecological processes and health of their hosts. This is particularly important for groups of animals currently facing conservation issues, such as reptiles. The diversity of species and supra-specific taxa of microparasites and macroparasites (such as helminths and arthropods) present in non-avian reptiles in Chile was analyzed through a systematic review. A total of 49 scientific documents (thesis projects, abstracts in congresses, book chapters and peer-reviewed articles) concerning parasites, taxonomic descriptions and parasite ecology were included in this review. The suborder Iguania was among the most studied group with 35 native species recognized as hosts of parasites and 39 species of parasites reported up to the category of species or genus. Liolaemus tenuis was the species with the most taxa of recorded parasites (11 taxa, and only three to species level), but Liolaemus chillanensis had the highest number of identified species of parasites. In addition, only one native species of Serpentes, one of Gymnophthalmoidea, and two of Gekkota, as well as some reports of exotic species, were recorded as hosts. Among parasites, Trombidiformes was the richest order with 10 species from the superfamily Pterygosomatoidea and 16 species from Trombiculoidea. Current knowledge about the richness of helminths is very limited and there were only a few records of microparasites. In general, there is an urgent need for the development of collaborative works between specialists in reptile taxonomy and epidemiology in parasitology destined to evaluate the consequences that reptiles and their parasites will suffer due to the ongoing processes of habitat loss, climate change and the still present taxonomic issues of the native reptiles.

Pathogens, parasites, and parasitoids of ants: a synthesis of parasite biodiversity and epidemiological traits

1.AbstractAnts are among the most ecologically successful organisms on Earth, with a global distribution and diverse nesting and foraging ecologies. Ants are also social organisms, living in crowded, dense colonies that can range up to millions of individuals. Understanding the ecological success of the ants requires understanding how they have mitigated one of the major costs of social living-infection by parasitic organisms. Additionally, the ecological diversity of ants suggests that they may themselves harbor a diverse, and largely unknown, assemblage of parasites. As a first step, we need to know the taxonomic and functional diversity of the parasitic organisms infecting ants. To that end, we provide a comprehensive review of the parasitic organisms infecting ants by collecting all extant records. We synthesize major patterns in parasite ecology by categorizing how parasites encounter their ant hosts, whether they require host death as a developmental necessity, and how they transmit to future hosts.We report 1,415 records of parasitic organisms infecting ants, the majority of which come from order Diptera (34.8%), phylum Fungi (25.6%), and order Hymenoptera (25.1%). Most parasitic organisms infecting ants are parasitoids (89.6%), requiring the death of their host as developmental necessity and most initially encounter their hosts in the extranidal environment (68.6%). Importantly, though most parasitic organisms infecting ants only need a single host to complete their life cycle (89.2%), the vast majority need to leave the nest before transmission to the next ant host can occur (88.3%), precluding ant-to-ant transmission within the nest. With respect to the host, we only found records for 9 out of 17 extant ant sub-families, and for 82 out of the currently recognized 334 ant genera. Though there is likely bias in the records reported, both host and parasite ecological traits and evolutionary histories underlie the pattern of ant-parasite association reported here. This work provides a foundation for future work that will begin to untangle the ecological drivers of ant-parasite relationships and the evolutionary implications thereof.