Wildfires modify the parasite loads of invasive cane toads

The frequency and severity of wildfires are increasing due to anthropogenic modifications to habitats and to climate. Post-fire landscapes may advantage invasive species via multiple mechanisms, including changes to host–parasite interactions. We surveyed the incidence of endoparasitic lungworms ( Rhabdias pseudosphaerocephala ) in invasive cane toads ( Rhinella marina ) in near-coastal sites of eastern Australia, a year after extensive fires in this region. Both the prevalence of infection and number of worms in infected toads increased with toad body size in unburned areas. By contrast, parasite load decreased with toad body size in burned areas. By killing moisture-dependent free-living lungworm larvae, the intense fires may have liberated adult cane toads from a parasite that can substantially reduce the viability of its host. Smaller toads, which are restricted to moist environments, did not receive this benefit from fires.

Download Full-text

Erythraeid larvae parasitizing dragonflies in Zambia—description of Leptus (Leptus) chingombensis sp. nov. with data on biology and ecology of host-parasite interactions

Systematic and Applied Acarology ◽

10.11158/saa.24.5.6 ◽

2019 ◽

Vol 24 (5) ◽

pp. 790

Author(s):

Rafał Bernard ◽

Magdalena Felska ◽

Joanna Mąkol

Keyword(s):

Dna Barcode ◽

Morphological Characteristics ◽

Parasite Load ◽

Ventral Side ◽

Habitat Conditions ◽

Local Character ◽

Host Parasite Interactions ◽

Group Variation ◽

The Common ◽

Host Parasite

A survey of odonate fauna in Zambia (Central Province, Luano District) resulted in discovery of ectoparasitic larvae of Leptus (L.) chingombensis sp. nov. (Trombidiformes: Parasitengona, Erythraeidae) on four species of dragonflies (Odonata) representing four different families assigned to Zygoptera and Anisoptera. The morphological characteristics of the new species is supported with DNA barcode sequence. Despite some intra-group variation related to relatively large sample, the morphological and genetic consistence confirm the common specific identity of the material. A brief comparison of Leptus spp. hitherto known from the Afrotropic as larvae is given. Supplementary data to the descriptions of Leptus (L.) bicristatus Fain et Elsen, 1987, Leptus (L.) aldonae Haitlinger, 1987 and Leptus (L.) soddagus Haitlinger, 1990, based on examination of type material, are provided. In the case of L. (L.) chingombensis sp. nov., the parasite load reached high, previously not recorded for Odonata–terrestrial Parasitengona association values, attaining at 44 and 49 larvae. Clear topic preferences towards the ventral side of the host’s body were recorded, with an additional tendency to distal parts of synthorax and the ventral depression of the abdomen. We hypothesize that the infestation did not take place synchronously at dragonflies emergence, but consisted in repeated infestation events during the recurrent appearance of dragonflies in the contact microhabitat occupied by Leptus. The very local character of the finding along with the regular appearance of larvae parasitizing dragonflies, obviously favoured by specific habitat conditions, no doubts confirms the non-accidental nature of the phenomenon.

Download Full-text

Host-parasite interactions between the piranha Pygocentrus nattereri (Characiformes: Characidae) and isopods and branchiurans (Crustacea) in the rio Araguaia basin, Brazil

Neotropical Ichthyology ◽

10.1590/s1679-62252004000200006 ◽

2004 ◽

Vol 2 (2) ◽

pp. 93-98 ◽

Cited By ~ 10

Author(s):

Lucélia Nobre Carvalho ◽

Rafael Arruda ◽

Kleber Del-Claro

Keyword(s):

Body Size ◽

Mean Intensity ◽

Feeding Sites ◽

Host Parasite Interactions ◽

Ecological Aspects ◽

Field Samples ◽

Pygocentrus Nattereri ◽

The Tropics ◽

Host Parasite ◽

Ventral Area

In the tropics, studies on the ecology of host-parasite interactions are incipient and generally related to taxonomic aspects. The main objective of the present work was to analyze ecological aspects and identify the metazoan fauna of ectoparasites that infest the piranha, Pygocentrus nattereri. In May 2002, field samples were collected in the rio Araguaia basin, State of Goiás (Brazil). A total of 252 individuals of P. nattereri were caught with fishhooks and 32.14% were infested with ectoparasite crustaceans. The recorded ectoparasites were branchiurans, Argulus sp. and Dolops carvalhoi and the isopods Braga patagonica, Anphira branchialis and Asotana sp. The prevalence and mean intensity of branchiurans (16.6% and 1.5, respectively) and isopods (15.5% and 1.0, respectively) were similar. Isopods were observed in the gills of the host; branchiurans were more frequent where the skin was thinner, and facilitated attachment and feeding. The ventral area, the base of the pectoral fin and the gular area were the most infested areas. The correlations between the standard length of the host and the variables intensity and prevalence of crustaceans parasitism, were significant only for branchiurans (rs = 0.2397, p = 0.0001; chi2 = 7.97; C = 0.19). These results suggest that both feeding sites and body size probably play an important role in the distribution and abundance of ectoparasites.

Download Full-text

Effect of environmental variables and their interaction on gordiid hairworm larvae (Nematomorpha)

Journal of Helminthology ◽

10.1017/s0022149x21000420 ◽

2021 ◽

Vol 95 ◽

Author(s):

C.L. Achiorno ◽

G. Minardi ◽

L. Ferrari

Keyword(s):

Freshwater Ecosystems ◽

Effect Of Temperature ◽

Extreme Temperatures ◽

Free Living ◽

Temperature Variations ◽

Host Parasite Interactions ◽

Effects Of Ph ◽

Chordodes Nobilii ◽

Increasing Temperature ◽

Host Parasite

Abstract The different stages of the life cycle of parasites are important components of ecosystems. Changes in environmental conditions may affect free-living stages, host–parasite interactions and ecosystem functioning. The larvae of Chordodes nobilii, which belongs to the parasitic phylum Nematomorpha, are susceptible to extreme temperatures and different pollutants, but the effects of pH and moderate temperature variations have not been evaluated yet. Our objective was to assess the effect of temperature, pH and their interaction on the infectivity of C. nobilii larvae to Aedes aegypti larvae over time. Larvae were treated with factorial combinations of temperature (18, 23 and 28°C), pH (7, 8 and 9) and time periods (24 and 48 h). Results show a highly significant interaction among all variables. The highest infectivity was recorded at 18°C and pH 7 at 24 and 48 h, and the lowest one at 28°C and pH 8 at 24 and 48 h. Infectivity differed significantly among the three temperatures only at pH 8 and 48 h, decreasing with increasing temperature. Our study is the first report of the effect of pH on a Nematomorpha species and suggests that the infectivity of C. nobilii larvae may be affected negatively by an increase in temperature and its interaction with pH and time. Since parasites must be considered for a better understanding of the effects of stressors on freshwater ecosystems, our results may help in the design and analysis of studies of anthropogenic impact.

Download Full-text

To delay once or twice: the effect of hypobiosis and free-living stages on the stability of host–parasite interactions

Journal of The Royal Society Interface ◽

10.1098/rsif.2007.1282 ◽

2008 ◽

Vol 5 (25) ◽

pp. 919-928 ◽

Cited By ~ 11

Author(s):

Sabrina Gaba ◽

Sébastien Gourbière

Keyword(s):

Population Dynamics ◽

Life Cycle ◽

Time Delay ◽

Host Population ◽

Previous Attempt ◽

Maximal Effect ◽

Parasite Life Cycle ◽

Free Living ◽

Host Parasite Interactions ◽

Host Parasite

The life cycle of many endoparasites can be delayed by free-living infective stages and a developmental arrestment in the host referred to as hypobiosis. We investigated the effects of hypobiosis and its interaction with delay in the free-living stages on host–parasite population dynamics by expanding a previous attempt by Dobson & Hudson. When the parasite life cycle does not include free-living stages, hypobiosis destabilizes the host–parasite interactions, irrespective of the assumptions about the regulation of the host population dynamics. Interestingly, the destabilizing effect varies in a nonlinear way with the duration of hypobiosis, the maximal effect being expected for three to five months delay. When the parasite life cycle involves free-living stages, hypobiosis of short or intermediate duration increases the destabilizing effect of the first time delay. However, hypobiosis of a duration of five months or more can stabilize interactions, irrespective of the regulation of the host population dynamics. Overall, we confirmed that hypobiosis is an unusual time delay as it can stabilize a two-way interaction. Contrary to the previous conclusions, such an atypical effect does not require self-regulation of the host population, but instead depends on the existence of free-living stages.

Download Full-text

Global stability and Hopf bifurcation of a host–parasite system

International Journal of Biomathematics ◽

10.1142/s1793524517500474 ◽

2017 ◽

Vol 10 (04) ◽

pp. 1750047

Author(s):

Xuerui Wei ◽

Zhipeng Qiu

Keyword(s):

Hopf Bifurcation ◽

Time Scale ◽

Sufficient Conditions ◽

Host Population ◽

Complete Analysis ◽

Logistic Growth ◽

Free Living ◽

Dynamical Mechanism ◽

Host Parasite Interactions ◽

Host Parasite

Understanding the dynamical mechanism of the host–parasite interactions is one of important issues on host–parasite association. In this paper, we formulate a three-dimensional host–macroparasite system to describe the host–parasite interactions, which includes the logistic growth rate of host population, the important free-living stage and the host fecundity reduction due to parasite infection. The purpose of the paper is to investigate the asymptotical behavior of the system. By using the properties of the solution to non-autonomous linear system, the basic production number [Formula: see text] is proved to be a threshold which determines the outcome of the parasites. If [Formula: see text], the parasite will eventually die out, and if [Formula: see text] the parasite will be uniformly persistent. Hopf bifurcation of the system is further studied, and sufficient conditions for the Hopf bifurcation are obtained. By using the singular perturbation techniques, the system is separated into two time scales with a faster time scale for the free-living infective particles and a slower time scale for the population dynamics of host and parasite, and then a complete analysis of the dynamics on the slow manifold is conducted. The theoretical results show that the level of aggregation of parasites within host may influence the persistence and stability of the system.

Download Full-text

Temperature during the free-living phase of an ectoparasite influences the emergence pattern of the infective phase

Parasitology ◽

10.1017/s0031182013000929 ◽

2013 ◽

Vol 140 (11) ◽

pp. 1357-1367 ◽

Cited By ~ 8

Author(s):

M. AMAT-VALERO ◽

M. A. CALERO-TORRALBO ◽

F. VALERA

Keyword(s):

Environmental Influence ◽

Abiotic Factors ◽

Life Cycles ◽

Detailed Knowledge ◽

Free Living ◽

Emergence Period ◽

Host Parasite Interactions ◽

Emergence Rate ◽

Emergence Date ◽

Host Parasite

SUMMARYUnderstanding the population dynamics and co-evolution of host–parasite systems requires detailed knowledge of their phenology which, in turn, requires a deep knowledge of the effect of abiotic factors on the life cycles of organisms. Temperature is known to be a key environmental influence that participates in the regulation of diapause. Yet, not much is known about the effect of temperature on the free-living stages of true parasites and how it may influence host–parasite interactions. Here we experimentally study the effect of ambient temperature on overwintering pupae ofCarnus hemapterus(Diptera, Carnidae), an ectoparasitic fly of various bird species. We also test whether chilling is a prerequisite for completion of diapause in this species. In the course of three winter seasons we experimentally exposed carnid pupae from nests of various host species to spring temperatures with and without chilling and recorded the emergence patterns in experimental and control groups. Experimental groups showed an advanced emergence date, a lower emergence rate and, consequently, a protracted emergence period. Chilling had no obvious effect on the start of emergence but it did advance the mean emergence date, shortened the length of the emergence period when compared with the control treatment and increased the emergence rate when compared with the spring treatment. This study identifies an environmental cue, namely temperature during the free-living stage, affecting the emergence of a widespread parasite and demonstrates the plasticity of diapause in this parasite. Our findings are of potential significance in understanding host–parasite interactions.

Download Full-text

Mesoscale spatiotemporal variability in a complex host-parasite system influenced by intermediate host body size

PeerJ ◽

10.7717/peerj.3675 ◽

2017 ◽

Vol 5 ◽

pp. e3675 ◽

Cited By ~ 3

Author(s):

Sara M. Rodríguez ◽

Nelson Valdivia

Keyword(s):

Body Size ◽

Parasite Burden ◽

Spatiotemporal Variability ◽

Intermediate Hosts ◽

Host Body ◽

Host Parasite Interactions ◽

Essential Components ◽

Host Parasite ◽

Parasite Exposure ◽

Host Body Size

Background Parasites are essential components of natural communities, but the factors that generate skewed distributions of parasite occurrences and abundances across host populations are not well understood. Methods Here, we analyse at a seascape scale the spatiotemporal relationships of parasite exposure and host body-size with the proportion of infected hosts (i.e., prevalence) and aggregation of parasite burden across ca. 150 km of the coast and over 22 months. We predicted that the effects of parasite exposure on prevalence and aggregation are dependent on host body-sizes. We used an indirect host-parasite interaction in which migratory seagulls, sandy-shore molecrabs, and an acanthocephalan worm constitute the definitive hosts, intermediate hosts, and endoparasite, respectively. In such complex systems, increments in the abundance of definitive hosts imply increments in intermediate hosts’ exposure to the parasite’s dispersive stages. Results Linear mixed-effects models showed a significant, albeit highly variable, positive relationship between seagull density and prevalence. This relationship was stronger for small (cephalothorax length >15 mm) than large molecrabs (<15 mm). Independently of seagull density, large molecrabs carried significantly more parasites than small molecrabs. The analysis of the variance-to-mean ratio of per capita parasite burden showed no relationship between seagull density and mean parasite aggregation across host populations. However, the amount of unexplained variability in aggregation was strikingly higher in larger than smaller intermediate hosts. This unexplained variability was driven by a decrease in the mean-variance scaling in heavily infected large molecrabs. Conclusions These results show complex interdependencies between extrinsic and intrinsic population attributes on the structure of host-parasite interactions. We suggest that parasite accumulation—a characteristic of indirect host-parasite interactions—and subsequent increasing mortality rates over ontogeny underpin size-dependent host-parasite dynamics.

Download Full-text

Off-host longevity of the winged dispersal stage ofCarnus hemapterus(Insecta: Diptera) modulated by gender, body size and food provisioning

Parasitology ◽

10.1017/s0031182018001300 ◽

2018 ◽

Vol 146 (2) ◽

pp. 241-245 ◽

Cited By ~ 4

Author(s):

Jesús Veiga ◽

Eulalia Moreno ◽

Jesús Benzal ◽

Francisco Valera

Keyword(s):

Body Size ◽

Food Provisioning ◽

Host Parasite Interactions ◽

Dispersal Stage ◽

Carnus Hemapterus ◽

Host Parasite ◽

The Impact ◽

Infectious Potential ◽

Critical Aspects ◽

Temporal Dispersal

AbstractHighlighting the dispersal ecology of parasites is important for understanding epidemiological, demographic and coevolutionary aspects of host–parasite interactions. Yet, critical aspects of the dispersal stage of parasites, such as longevity and the factors influencing it, are poorly known. Here we study the lifespan of the dispersal stage of an ectoparasitic dipteran,Carnus hemapterus, and the impact of gender, body size and food provisioning on longevity. We found that freshly emerged imagoes survive at most less than 4 days. Longevity increased with body size and, since this parasite exhibits sexual size dimorphism, the bigger females lived longer than males. However, controlling for body size suggests that males lived relatively longer than females. Furthermore, a humid environment and food provisioning (flowers) significantly increased individual life spans. We discuss the relative importance of spatial and temporal dispersal in relation to the infectious potential of this parasite.

Download Full-text