Host Parasite Research Articles

Use of stable isotope ratio analysis to investigate the biology and clinical significance of seal parasites.

Stranded seals are often infected with a broad range of parasites, although whether they are the cause of significant morbidity or an incidental finding is usually unclear. In this study we used stable isotope ratio analysis, a method frequently used to investigate food webs, to explore the extent to which common seal parasites feed directly on host tissue and fluids or absorb host-derived metabolites, which in turn may give an indication of their potential impact on the host's health. The trophic discrimination factor Δ15N for the nasal mite, Halarachne halichoeri, was mostly positive, ranging between −0.015 and 3.2‰ (n = 6), while for the Acanthocephalan worm, Corynosoma strumosum and the anisakid nematode, Pseudoterranova decipiens, Δ15N ranged between −4.2 and −2.0‰ (n = 7), and between −6.7 and −0.8‰ (n = 5) respectively. In the case of the lungworm, Otostrongylus circumlitus, Δ15N measured between −5.6 and 0‰ for worms collected in the stomach (n = 5), between −1.1 and 0.2‰ for worms collected from the heart (n = 3), between −0.7 and 1.9‰ for worms situated in the lungs (n = 4). Based on Δ15N, parasites could be clearly divided into those that were on a higher trophic level than their host suggesting a predator–prey-like relationship, and those that were not. It is hypothesized that Δ15N may be indicative of the clinical significance of parasite–host associations.

Host–parasite interaction: an insight into the growth and physiological responses of sandalwood and associated host species

IntroductionSandalwood (Santalum album L.) is categorized as vulnerable in the IUCN Red list and is also an industrially important tree species valued for its heartwood and aromatic oil. Sandalwood is a semi-root parasite tree that relies on its host plants for its water and nutrient requirements. Therefore, there is need to understand the growth and physiological interactions between sandalwood and its hosts.MethodsSandalwood were planted with ten different host species viz., Syzygium cumini, Punica granatum, Phyllanthus emblica, Melia dubia, Leucaena leucocephala, Dalbergia sissoo, Casuarina equisetifolia, Citrus aurantium, Azadirachta indica and Acacia ampliceps to assess the interactive effect on the change in growth and physiology of both sandalwood and host tree species.ResultsThe findings revealed that sandalwood grown with hosts D. sissoo and C. equisetifolia showed higher growth performance, while among hosts, S. cumini, followed by C. aurantium and L. leucocephala, showed better growth and physiobiochemical traits. The stepwise regression analysis and trait modeling indicated that the six traits, namely, plant height, photosynthetic rate, relative water content, water potential, intercellular CO2 concentration, and total soluble protein, contributed greater growth in the sandalwood, while four traits, namely, water potential, osmotic potential, leaf area, and total soluble protein, contributed greater growth in the host species. The traits modeling study predicted greater growth of sandalwood with the hosts D. sissoo and C. equisetifolia, whereas among host species, prediction revealed greater growth of S. cumini and C. aurantium.DiscussionThe study concluded that host–parasite interaction modulated the growth and physiological processes in both sandalwood and hosts and sandalwood plantations can be successfully developed with the hosts D. sissoo and C. equisetifolia.

The Tilapia Cyst Tissue Enclosing the Proliferating Myxobolus bejeranoi Parasite Exhibits Cornified Structure and Immune Barrier Function.

Myxozoa, a unique group of obligate endoparasites within the phylum Cnidaria, can cause emerging diseases in wild and cultured fish populations. Recently, the myxozoan Myxobolus bejeranoi has been identified as a prevalent pathogen infecting the gills of cultured hybrid tilapia, leading to systemic immune suppression and considerable mortality. Here, we employed a proteomic approach to examine the impact of M. bejeranoi infection on fish gills, focusing on the structure of the granulomata, or cyst, formed around the proliferating parasite to prevent its spread to surrounding tissue. Enrichment analysis showed increased immune response and oxidative stress in infected gill tissue, most markedly in the cyst's wall. The intense immune reaction included a consortium of endopeptidase inhibitors, potentially combating the myxozoan arsenal of secreted proteases. Analysis of the cyst's proteome and histology staining indicated that keratin intermediate filaments contribute to its structural rigidity. Moreover, we uncovered skin-specific proteins, including a grainyhead-like transcription factor and a teleost-specific S100 calcium-binding protein that may play a role in epithelial morphogenesis and cysts formation. These findings deepen our understanding of the proteomic elements that grant the cyst its distinctive nature at the critical interface between the fish host and myxozoan parasite.

Co-phylogeographic structure in a disease-causing parasite and its oyster host.

With the increasing affordability of next-generation sequencing technologies, genotype-by-sequencing has become a cost-effective tool for ecologists and conservation biologists to describe a species' evolutionary history. For host–parasite interactions, genotype-by-sequencing can allow the simultaneous examination of host and parasite genomes and can yield insight into co-evolutionary processes. The eastern oyster, Crassostrea virginica, is among the most important aquacultured species in the United States. Natural and farmed oyster populations can be heavily impacted by ‘dermo’ disease caused by an alveolate protist, Perkinsus marinus. Here, we used restricted site-associated DNA sequencing (RADseq) to simultaneously examine spatial population genetic structure of host and parasite. We analysed 393 single-nucleotide polymorphisms (SNPs) for P. marinus and 52,100 SNPs for C. virginica from 36 individual oysters from the Gulf of Mexico (GOM) and mid-Atlantic coastline. All analyses revealed statistically significant genetic differentiation between the GOM and mid-Atlantic coast populations for both C. virginica and P. marinus, and genetic divergence between Chesapeake Bay and the outer coast of Virginia for C. virginica, but not for P. marinus. A co-phylogenetic analysis confirmed significant coupled evolutionary change between host and parasite across large spatial scales. The strong genetic divergence between marine basins raises the possibility that oysters from either basin would not be well adapted to parasite genotypes and phenotypes from the other, which would argue for caution with regard to both oyster and parasite transfers between the Atlantic and GOM regions. More broadly, our results demonstrate the potential of RADseq to describe spatial patterns of genetic divergence consistent with coupled evolution.

Tradeoffs in access to light and root networks of established host trees for restoration planting of the root hemiparasite Santalum paniculatum

Restoration of root hemiparasite trees, such as Hawaiʻi's endemic Santalum species (ʻiliahi), may benefit from underplanting in stands of suitable hosts like the nitrogen‐fixing native tree, Acacia koa (koa). At a pasture site on Hawaiʻi Island previously reforested with koa, we underplanted seedlings of the island‐endemic sandalwood species, Santalum paniculatum, to examine the tradeoff between access to an established root network (distance to the nearest koa tree) under variable overstory shading (8.8–90.1% canopy openness range) during regeneration establishment. We hypothesized that there is an optimal parasite–host spacing and canopy openness that balance parasitic resource transfer with light availability. ʻIliahi seedling survival was 96% with no survival treatment differences. ‘Iliahi seedling growth was positively related to canopy openness but negatively related to the distance to the nearest koa tree, and the slope of these relationships increased over time. Leaf photosynthetic light compensation points, light saturation points, and stomatal density mostly followed similar trends as growth. These results demonstrate that ‘iliahi can be successfully underplanted in an established koa stand, which benefits ‘iliahi plantings and contributes to diversifying initial restoration and reforestation plantings. There appears to be a significant tradeoff in planting distance between benefits from and competition with the host; however, the improvement in growth with increased canopy openness appeared to be much greater than the effect of planting distance. Underplanting into an established host stand with sufficient canopy openness can help restore functionally compatible and abundant ‘iliahi regeneration into forests.

2D and 3D visualization of herbaceous plant–plant contact zones using high‐resolution X‐ray computed tomography (HRXCT)

Societal Impact StatementParasitic plants that deprive crops of water and nutrients are an increasingly concerning food security issue, affecting the livelihood of millions of subsistence, small‐ and mid‐scale farmers. An in‐depth understanding of parasite–host interactions is required to develop species‐specific and ecologically sustainable parasite management methods. The non‐invasive visualization of herbaceous contact zones, applicable to diverse parasite–host pathosystems presented in this study, brings methodological advance to the research of biotic interactions between crops and plant parasites belonging to the most devastating parasitic plant family (Orobanchaceae). This work also provides first insights into how the parasites' feeding organ displaces host tissue beyond the direct parasite–host interface.SummaryHigh‐resolution X‐ray computed tomography (HRXCT) enables sectioning‐free two‐dimensional imaging of biological structures and reconstruction of three‐dimensional objects. Although its application is common in many areas of biomedicine and despite its flexibility regarding resolution levels, the technology remains underutilized in the plant sciences. Here, we explored HRXCT for the study of parasitic plant–plant interactions by developing protocols to access soft‐tissue host–parasite contact zones at cell‐level resolution. We tested various sample preparation methods and contrast stains for their efficiency to improve the imaging of haustorium samples. In doing so, we achieved cellular resolution with the visible cellular organization of haustorial structures, especially of the vascular system. Fresh stained and dehydrated sample preparation of soft haustoria enables the highest spatial resolution with fine‐cellular discrimination of haustorium versus host cells. Application of cell‐level resolved HRXCT to five pathosystems: Alectra‐cowpea, Phelipanche‐tomato, Phtheirospermum‐tomato, Rhamphicarpa‐tomato, and Striga‐sorghum highlighted a life history‐specific organization and uncovered an as yet undescribed internal displacement of host tissue at parasite–host interfaces. Following image‐based training, our HRXCT approach could invoke AI‐based cell recognition for automated parasite cell–host cell differentiation. Superseding extensive microsectioning for 3D imaging, the newly established HRXCT protocol for 2D‐ and 3D‐visualization of herbaceous plant–plant contact zones and the first insights gained from it, is useful for mid‐throughput, comparative studies of parasitic plant–host interactions.

Expression of IL-10 and TGF-β1 in horses experimentally infected with T. equi merozoites is associated with antibody production but not modulation of pro-inflammatory responses.

Theileria equi (T. equi) is an apicomplexan parasite that causes severe hemolytic anemia in equids. Presently, there is inadequate knowledge of the immune responses induced by T. equi in equid hosts impeding understanding of the host parasite relationship and development of potent vaccines for control of T. equi infections. The objective of this study was to evaluate the host-parasite dynamics between T. equi merozoites and infected horses by assessing cytokine expression during primary and secondary parasite exposure, and to determine whether the pattern of expression correlated with clinical indicators of disease. Our findings showed that the expression of pro-inflammatory cytokines was very low and inconsistent during both primary and secondary infection. There was also no correlation between the symptoms observed during primary infection and expression of the cytokines. This suggests that the symptoms might have occurred primarily due to hemolysis and likely not the undesirable effects of pro-inflammatory responses. However, IL-10 and TGF-β1 were highly expressed in both phases of infection, and their expression was linked to antibody production but not moderation of pro-inflammatory cytokine responses.

Great genetic diversity of vector-borne bacteria and protozoan in wild rodents from Guangxi, China.

Rodents are recognized as the hosts of many vector-borne bacteria and protozoan parasites and play an important role in their transmission and maintenance. Intensive studies have focused on their infections in vectors, especially in ticks, however, vector-borne bacterial and protozoan infections in rodents are poorly understood although human cases presenting with fever may due to their infection have been found. From May to October 2019, 192 wild rodents were trapped in wild environment of Guangxi Province, and the spleen samples were collected to reveal the presence of vector-borne bacterial and protozoan infections in them. The microorganisms in rodents were identified by detecting their DNA using (semi-)nested PCR. All the PCR products of the expected size were subjected to sequencing, and then analyzed by BLASTn. Furthermore, all the recovered sequences were subjected to nucleotide identity and phylogenetic analyses. As a result, 192 rodents representing seven species were captured, and Bandicota indica were the dominant species, followed by Rattus andamanensis. Based on the (semi-)nested PCR, our results suggested that Anaplasma bovis, Anaplasma capra, Anaplasma ovis, Anaplasma phagocytophilum, "Candidatus Neoehrlichia mikurensis", "Candidatus E. hainanensis", "Candidatus E. zunyiensis", three uncultured Ehrlichia spp., Bartonella coopersplainsensis, Bartonella tribocorum, Bartonella rattimassiliensis, Bartonella silvatica, two uncultured Bartonella spp., Babesia microti and diverse Hepatozoon were identified in six rodent species. More importantly, six species (including two Anaplasma, two Bartonella, "Ca. N. mikurensis" and Bab. microti) are zoonotic pathogens except Anaplasma bovis and Anaplasma ovis with zoonotic potential. Furthermore, dual infection was observed between different microorganisms, and the most common type of co-infection is between "Ca. N. mikurensis" and other microorganisms. Additionally, potential novel Bartonella species and Hepatozoon species demonstrated the presence of more diverse rodent-associated Bartonella and Hepatozoon. The results in this work indicated great genetic diversity of vector-borne infections in wild rodents, and highlighted the potential risk of human pathogens transmitted from rodents to humans through vectors.

The myxozoans Myxobolus cerebralis and Tetracapsuloides bryosalmonae modulate rainbow trout immune responses: quantitative shotgun proteomics at the portals of entry after single and co-infections.

Little is known about the proteomic changes at the portals of entry in rainbow trout after infection with the myxozoan parasites, Myxobolus cerebralis, and Tetracapsuloides bryosalmonae. Whirling disease (WD) is a severe disease of salmonids, caused by the myxosporean M. cerebralis, while, proliferative kidney disease (PKD) is caused by T. bryosalmonae, which instead belongs to the class Malacosporea. Climate change is providing more suitable conditions for myxozoan parasites lifecycle, posing a high risk to salmonid aquaculture and contributing to the decline of wild trout populations in North America and Europe. Therefore, the aim of this study was to provide the first proteomic profiles of the host in the search for evasion strategies during single and coinfection with M. cerebralis and T. bryosalmonae. One group of fish was initially infected with M. cerebralis and another group with T. bryosalmonae. After 30 days, half of the fish in each group were co-infected with the other parasite. Using a quantitative proteomic approach, we investigated proteomic changes in the caudal fins and gills of rainbow trout before and after co-infection. In the caudal fins, 16 proteins were differentially regulated post exposure to M. cerebralis, whereas 27 proteins were differentially modulated in the gills of the infected rainbow trout post exposure to T. bryosalmonae. After co-infection, 4 proteins involved in parasite recognition and the regulation of host immune responses were differentially modulated between the groups in the caudal fin. In the gills, 11 proteins involved in parasite recognition and host immunity, including 4 myxozoan proteins predicted to be virulence factors, were differentially modulated. The results of this study increase our knowledge on rainbow trout co-infections by myxozoan parasites and rainbow trout immune responses against myxozoans at the portals of entry, supporting a better understanding of these host-parasite interactions.

Parasitic success of the pathogenic plant Phelipanche ramosa (L.) Pomel. (Orobanchaceae) differs in some re‐infected versus naïve tomato cultivars

AbstractPlants are exposed to infection and predation by organisms from most kingdoms of life, including their own. Layers of molecular defence mechanisms have evolved to limit damage and disease from microbial and insect pathogens, and plants can also defend themselves against attack by members of their own kingdom. These so‐called parasitic plants attach to and take up nutrients from a host plant. It is not yet known whether parasites belonging to the plant kingdom can elicit a systemic defence response in their hosts, to which they have much more in common molecularly than viruses and fungi. To gain insight as to whether previous infection reduces the susceptibility of a host, we used two successive rounds of infection of the same host plants with the holoparasitic plant Phelipanche ramosa (‘broomrape,’ Orobanchaceae). We tested seven cultivars of tomato, and found that the ‘Moneymaker’ cultivar was re‐infested at a lower rate than its naïve counterpart and, if pre‐infested, supported fewer parasites than other cultivars. We collected tissue for RNA sequencing at the host–parasite interface of two cultivars, ‘Moneymaker’ and ‘Zuckertraube’, the latter of which showed no difference in susceptibility upon reinfection. These data revealed tomato cultivar‐specific transcriptional profiles in the parasite, including the upregulation of several peroxidase genes in parasites infecting ‘Moneymaker’, compared to ‘Zuckertraube’. Furthermore, we detected the upregulation of lignin biosynthesis genes in ‘Moneymaker’ tomato plants when they were pre‐infected with the holoparasitic plant. Together, our data suggest that some tomato cultivars may be naturally able to build up defences against parasitic plant infection. This could be relevant for agriculture, in that cuttings or other forms of vegetative propagation of pre‐infected tomato plants can prime crops to withstand field infestations more effectively.

Detection of Gnathostoma spinigerum larva in the brain with complete follow-up after surgical treatment of human neurognathostomiasis

Human gnathostomiasis is a food-borne zoonotic helminthic infection widely reported in Latin America, Asia, and Southeast Asia. Consuming raw, or under-cooked fresh-water fish is the leading cause of this helminthic infection, which is clinically characterized by signs of inflammation, itching sensation, or irritation with migratory swelling. Neurological symptoms resulting from neurognathostomiasis vary, and there is scant information due to the rareness of patient brain samples. This study aimed to demonstrate the first evidence of human neurognathostomiasis by the detection of Gnathostoma spinigerum larva in patient's brain during craniotomy, supported by histopathological, immunological and proteomic evidence. Clinical symptoms were obtained from medical history and physical examination with laboratory investigations, including magnetic resonance imaging (MRI), left temporal craniotomy, histopathology of brain tissue, and Western blot analysis, were performed to elucidate the causative pathogens for diagnosis. In addition, the host–parasite interaction of the parasite invading the patient's brain was characterized through proteomics. Histopathology revealed worms with the characteristic cuticular spines of G. spinigerum which were detected and identified. These histopathological findings were consistent with a positive Western blot showing a 24-kDa reactive-band for gnathostomiasis. Proteomic analysis revealed the presence of G. spinigerum serpin and serine protease in the patient's serum. Moreover, the leucine-rich alpha-2-glycoprotein was indicated as a systemic biomarker of early brain injury related to invasion by G. spinigerum. Therefore, our study provides the initial evidence of human neurognathostomiasis due to G. spinigerum larval invasion along with successful craniotomy and proven larval detection including complete follow-up, and the disease prognosis after surgical treatment.

Volatiles of symbiotic bacterial origin explain ectoparasitism and fledging success of hoopoes

BackgroundSome parasites use olfactory cues to detect their hosts and, since bacterial symbionts are partially responsible for animal odours, they could influence host parasitism. By autoclaving nest materials of hoopoe (Upupa epops) nests before reproduction started, we explored the hypothetical links between host-associated bacteria, volatiles and parasitism. During the nestling stage, we (i) estimated the level of ectoparasitism by chewing lice (Suborder Mallophaga) in adult hoopoe females and by Carnus haemapterus flies in nestlings, and (ii) characterized microbial communities and volatile profiles of nest environments (nest material and nest cavity, respectively) and uropygial secretions.ResultsExperimental nests had less diverse bacterial communities and more diverse volatile profiles than control nests, while occupants experienced lower intensity of parasitism in experimental than in control nests. The experiment also affected beta diversity of the microbial communities of nest material and of the volatiles of the nestling uropygial secretions. Moreover, microbial communities of uropygial secretions and of nest materials covaried with their volatile profiles, while the volatile profile of the bird secretions explained nest volatile profile. Finally, a subset of the volatiles and bacteria detected in the nest material and uropygial secretions were associated with the ectoparasitism intensity of both adult females and nestlings, and with fledging success.ConclusionsThese results show that a component of animal odours is linked with the microbial communities of the host and its reproductive environment, and emphasize that the associations between bacteria, ectoparasitism and reproductive success are partially mediated by volatiles of bacterial origin. Future work should focus on mechanisms underlying the detected patterns.

Catalog of the Chrysomelinae (Coleoptera: Chrysomelidae) deposited in the entomological collections of the Museu Paraense Emílio Goeldi (MPEG) and the Universidade do Estado do Pará (UEPA), Belém, Brazil

A comprehensive catalog is provided for most leaf beetles belonging to the Chrysomelinae subfamily, which are housed in the collections of two institutions in the state of Pará, located in northern Brazil: The Museu Paraense Emílio Goeldi (MPEG) and the Universidade do Estado do Pará (UEPA). The catalog includes detailed geographic distribution data for all species, along with new records and photographs (including two paratypes of Cryptostetha pereirai Bechyně, 1958, with descriptions of the aedeagus and spermatheca). Furthermore, information is provided on host plants, parasites, parasitoids, and predators associated with certain species.

Mapping of intermediate host snails for schistosomiasis in the Democratic Republic of Congo: a systematic review.

Schistosomiasis is a snail-borne disease that has a considerable impact on human and animal health, particularly in sub-Saharan Africa. The intermediate hosts of the schistosome parasites are freshwater snails of the genera Biomphalaria Preston, 1910 and Bulinus Müller, 1781. In order to identify existing gaps in the spread of the disease in the Democratic Republic of Congo (DRC), this study compiled the available knowledge of the distribution, population dynamics and ecology of the intermediate hosts of schistosomiasis. A systematic literature search was conducted in PubMed, Embase and Scopus for all malacological studies on schistosoma intermediate hosts in DRC published between 1927 and October 2022. A total of 55 records were found, of which 31 met the inclusion criteria: these were published field and experimental studies conducted in the DRC and focused on snails as intermediate hosts of schistosomes. The analysis of these studies revealed that more up-to-date data on the distribution of snail intermediate hosts in the DRC are needed. Moreover, ecological factors have been less studied for Bulinus species than for Biomphalaria species. These factors play a crucial role in determining suitable snail habitats, and the lack of comprehensive information poses a challenge in snail control. This review makes it clear that there are no current malacological data in the DRC. There is a clear need for molecular and ecological research to update the exact species status and population dynamics of all potential intermediate host species. This will facilitate targeted snail control measures that complement drug treatment in the control of schistosomiasis in the country.

Cellular dynamics of host − parasitoid interactions: Insights from the encapsulation process in a partially resistant host

Cotesia typhae is an eastern African endoparasitoid braconid wasp that targets the larval stage of the lepidopteran stem borer, Sesamia nonagrioides, a maize crop pest in Europe. The French host population is partially resistant to the Makindu strain of the wasp, allowing its development in only 40% of the cases. Resistant larvae can encapsulate the parasitoid and survive the infection. This interaction provides a very interesting frame for investigating the impact of parasitism on host cellular resistance. We characterized the parasitoid ovolarval development in a permissive host and studied the encapsulation process in a resistant host by dissection and histological sectioning compared to that of inert chromatography beads. We measured the total hemocyte count in parasitized and bead-injected larvae over time to monitor the magnitude of the immune reaction. Our results show that parasitism of resistant hosts delayed encapsulation but did not affect immune abilities towards inert beads. Moreover, while bead injection increased total hemocyte count, it remained constant in resistant and permissive larvae. We conclude that while Cotesia spp virulence factors are known to impair the host immune system, our results suggest that passive evasion could also occur.

Variation in prevalence and intensity of macroparasites in moose and their interactions with winter tick load in eastern Canada

Wild animals are infected with a large diversity and abundance of parasites that can affect their behavior, growth, body condition, and ultimately their survival. Although the adverse effects of parasites and the mechanisms involved in the interactions between a host and its parasites are generally well studied, much less is known about the additive or synergistic effects of multiple parasite species on a host. Moose populations in eastern Canada are infected by several species of endoparasites. In the last decades, the intensity of infestations by winter ticks, an ectoparasite, on moose have increased as a result of increased moose densities and favorable weather conditions that benefit winter tick survival. We aimed to document the diversity, intensity, prevalence, and distribution of different parasite species of moose in southern Quebec, Canada. We then evaluated the potential interaction between winter tick and endoparasites of moose, and we evaluated the effect of the simultaneous presence of ticks and endoparasites on moose body condition. To do so, we collected organs to identify and count endoparasite species, estimate winter tick abundance, and measure subcutaneous fat thickness from 174 hunted moose in fall 2019 in 8 regions of Quebec. Our results showed that the prevalence and intensity of winter tick and gastrointestinal parasites differed among regions, as well as the prevalence of the heart parasite Taenia krabbei and the intensity of lung parasite Echinoccocus granulosus. Moose body condition, however, was not influenced by the simultaneous presence of winter tick and endoparasites. The documentation of the interactive effects of multiple parasite species on a host is fundamental given that future environmental conditions in temperate climate will favor the reproduction, development, and survival of several parasite species, which could affect parasite diversity and abundance in the environment and modify host–parasite dynamics.

Shifts in host–parasitoid networks across community garden management and urban landscape gradients

AbstractBiological pest control relies on interactions between herbivores and their natural enemies. Maintaining this ecosystem service requires considering herbivore and natural enemy interactions and their response to anthropogenic change at multiple scales. In this study, we used ecological networks to quantify the network structure of interactions between herbivorous insects and their parasitoids. We examined how herbivore host abundance, parasitism rates, and shifts in network structure relate to changes in local habitat management and landscape context. We sampled herbivores and parasitoids in Brassica oleracea plants at 22 urban gardens in the Central Coast of California. At each site, we measured local management characteristics (e.g., vegetation, ground cover, canopy cover) and quantified surrounding landscape composition (e.g., urban, natural, open, and agricultural cover). For the eight sites with large enough networks, we calculated three network structure metrics (interaction richness, vulnerability, and functional complementarity). We then used generalized linear and mixed models to examine relationships between herbivore host abundance, parasitism rates, garden management and landscape characteristics, and network metrics. We found that both local management and landscape composition influenced parasitism, while only local factors affected host abundance and network structure. Higher network interaction richness was marginally associated with enhanced parasitism rates for two host species and lower parasitism rates for one host species. Our results suggest that local garden management decisions may shift the structure of host–parasitoid networks, which may subsequently affect host parasitism rates, but outcomes for biological pest control will likely vary across host species.

A conserved gastropod withdrawal circuit in Biomphalaria glabrata, an intermediate host for schistosomiasis.

Neuronal signals mediated by the biogenic amine serotonin (5-HT) underlie critical survival strategies across the animal kingdom. This investigation examined serotonin-like immunoreactive neurons in the cerebral ganglion of the panpulmonate snail Biomphalaria glabrata, a major intermediate host for the trematode parasite Schistosoma mansoni. Five neurons comprising the cerebral serotonergic F (CeSF) cluster of B. glabrata shared morphological characteristics with neurons that contribute to withdrawal behaviors in numerous heterobranch species. The largest member of this group, designated CeSF-1, projected an axon to the tentacle, a major site of threat detection. Intracellular recordings demonstrated repetitive activity and electrical coupling between the bilateral CeSF-1 cells. In semi-intact preparations, the CeSF-1 cells were not responsive to cutaneous stimuli but did respond to photic stimuli. A large FMRF-NH2-like immunoreactive neuron, termed C2, was also located on the dorsal surface of each cerebral hemiganglion near the origin of the tentacular nerve. C2 and CeSF-1 received coincident bouts of inhibitory synaptic input. Moreover, in the presence of 5-HT they both fired rhythmically and in phase. As the CeSF and C2 cells of Biomphalaria share fundamental properties with neurons that participate in withdrawal responses in Nudipleura and Euopisthobranchia, our observations support the proposal that features of this circuit are conserved in the Panpulmonata.NEW & NOTEWORTHY Neuronal signals mediated by the biogenic amine serotonin underlie critical survival strategies across the animal kingdom. This investigation identified a group of serotonergic cells in the panpulmonate snail Biomphalaria glabrata that appear to be homologous to neurons that mediate withdrawal responses in other gastropod taxa. It is proposed that an ancient withdrawal circuit has been highly conserved in three major gastropod lineages.

Anguilla anguilla vs Contracaecum rudolphii: Granuloma allows host tolerance and parasite survival

High survival of the nematode Contracaecum rudolphii in European eel, Anguilla anguilla L. despite an extensive recruitment of immune cells in granulomas is described. A total of 39 eel specimens captured in Canneviè lagoon (Northern Adriatic Sea, Italy) was obtained from local fishermen. The fish were examined for the presence of endoparasitic helminths. Twenty-six eels (67%) harbored third-stage larvae (L3) of Contracaecum rudolphii A and the intensity of infection ranged from 1 to 100 parasites per fish (mean 11.4). A total of 296 larvae were counted and 293 were alive and encysted in the serosa (primarily on external surface of the rectum) as conspicuous granulomas, appearing as white nodules. Histological sections showed a granuloma formed around an individual larva and consisted of three concentric cell layers, containing numerous mast cells (MCs), fibroblasts, macrophages, and epithelioid cells. Encysted larvae were also present in other layers of the intestinal wall, including the mucosa, where recruitment of macrophage aggregates in lamina propria was documented. Immunohistochemical investigations, applying eight antibodies raised against immune cell markers, revealed histamine and serotonin in MCs and inducible-nitric oxide synthase and toll-like receptor-2 in macrophages surrounding the parasite larvae. The study indicates that this innate cellular response in the eel has a chronic inflammatory character and keeps the nematode larvae arrested in a state allowing both host tolerance and parasite survival. The European eel serves as prey for birds and the high survival of C. rudolphii A larvae in the eel indicates that this fish species is a good paratenic host for the parasite allowing completion of its life cycle in birds.

Role of external nutrient supply in establishing host-sandalwood interactions

Sandalwood is semi root parasite plants that required host plant for water and nutrients. So, for successful sandalwood plantation, it is important to study the host parasite interactions and role of external supply of water and nutrient, both theoretically and practically. To find out long-term host species for sandalwood, a randomized block design experiment was conducted to identify the suitability of host and effect of externally supplied nutrient medium on sandalwood planted with five selected host (Alternanthera sp., Azadirachata indica, Dalbergia sissoo, Melia dubia, and Aquilaria malaccensis) and without host species. After 180 days of establishment, morphological traits were recorded and noted that plant height, collar diameter and root length was higher in Dalbergia sissoo and Melia dubia as compared to other host species. Significant enhancement in morphological traits was recorded with external supply of Hoagland nutrient medium. Similarly, higher shoot biomass and root biomass were noted in Dalbergia sissoo and Melia dubia under control as well as with externally supplied nutrient medium. While, maximum haustorial connections were formed with Dalbergia sissoo over studied host species. On the other hand physiological trait such as chlorophyll content was abundant in sandalwood grown with Dalbergia sissoo. Physiological parameters such photosynthetic rate, transpiration rate were higher in sandalwood cultivated with Dalbergia sissoo. Macronutrient such as nitrogen, phosphorus and potassium content was also higher in Dalbergia sissoo and Melia dubia. The results revealed that sandalwood could be grown successfully with Dalbergia sissoo and external supply of nutrients might enhance the growth and physiology of sandalwood.