Selected Wildlife Trematodes

Bolek, Matthew G.; Detwiler, Jillian T.; Stigge, Heather A.

doi:10.1007/978-3-030-18616-6_11

Cited by 12 publications

(6 citation statements)

References 153 publications

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“…These flukes have a complex life cycle that usually involves a freshwater snail and an arthropod with aquatic life stages as first and second intermediate hosts, and then an amphibian as final host. Commonly, amphibians get infected by preying on adult dragonflies (Bolek et al ., 2019). Most of the species recently identified and/or described from Mexican amphibians have been distinguished or authored by researchers from the group headed by Dr León-Règagnon using molecular characters in addition to morphology (e.g.…”

Section: Discussionmentioning

confidence: 99%

Research on helminths from Mexican amphibians: gaps, trends, and biases

2021

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We present a taxonomic, spatial, and thematic overview of the current state of knowledge on helminth parasites of Mexican amphibians. Sixty-six host species have been studied so far, representing 17.5% of the amphibian species distributed in Mexico. A total of 139 nominal species of helminths – 68 platyhelminths, 62 nematodes, three acanthocephalans, three annelids (hirudineans), and three arthropods (pentastomids) – have been recorded parasitizing these hosts. Most taxa found in larval stages have not been identified at the species level. The gastrointestinal nematode Aplectana itzocanensis exhibits the broadest host range, while the bladder fluke Gorgoderina attenuata and A. itzocanensis show the widest geographic distribution. Our analysis of helminthological studies evidenced gaps and biases on research efforts that have been devoted to relatively few host species, regions, and approaches. Most helminthological records come from two species, the cane toad Rhinella marina and the Montezuma's frog Lithobates montezumae, and most studies have focused on describing the helminth fauna of a host species in a particular location or on the description of new helminth species. The highest proportion of records corresponds to the Veracruzan biogeographic province, and helminth richness is significantly correlated with host richness and with total amphibian richness by biogeographic province. Only three provinces (Yucatan Peninsula, Pacific Lowlands, and Baja Californian) have positive, yet still low helminth species discovery effort. Based on our findings, we recommend pursuing research approaches unexplored in Mexico and we provide guidelines to improve research on helminths parasitizing amphibians.

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Section: Discussionmentioning

confidence: 99%

Research on helminths from Mexican amphibians: gaps, trends, and biases

2021

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“…However, schistosomes and echinostome trematodes differ in many aspects of their biology (i.e., represent different families of trematodes, differ in life cycle complexity, host species used). Further, no study has characterized the oxylipins of echinostome-infected snails despite their ubiquity in freshwater systems ( 85 ).…”

Section: Discussionmentioning

confidence: 99%

Density-Dependent Prophylaxis in Freshwater Snails Driven by Oxylipin Chemical Cues

Friesen

Sykes

et al. 2022

Front. Immunol.

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While animal aggregations can benefit the fitness of group members, the behaviour may also lead to higher risks of parasite infection as group density increases. Some animals are known to moderate their investment in immunity relative to the risk of infection. These animals exhibit density-dependent prophylaxis (DDP) by increasing their immune investment as group density increases. Despite being documented in many taxa, the mechanisms of DDP remain largely unexplored. Snails are known to aggregate and experience large fluctuations in density and serve as required hosts for many parasites. Further, they are known to use chemical cues to aggregate. To test whether freshwater snails exhibit DDP and investigate the role that chemical signaling compounds may play in triggering this phenomenon, we performed four experiments on the freshwater snail Stagnicola elodes, which is a common host for many trematode parasite species. First, we tested if DDP occurred in snails in laboratory-controlled conditions (control vs snail-conditioned water) and whether differences in exposure to chemical cues affected immune function. Second, we used gas chromatography to characterize fatty acids expressed in snail-conditioned water to determine if precursors for particular signaling molecules, such as oxylipins, were being produced by snails. Third, we characterized the oxylipins released by infected and uninfected field-collected snails, to better understand how differences in oxylipin cocktails may play a role in inducing DDP. Finally, we tested the immune response of snails exposed to four oxylipins to test the ability of specific oxylipins to affect DDP. We found that snails exposed to water with higher densities of snails and raised in snail-conditioned water had higher counts of haemocytes. Additionally, lipid analysis demonstrated that fatty acid molecules that are also precursors for oxylipins were present in snail-conditioned water. Trematode-infected snails emitted 50 oxylipins in higher amounts, with 24 of these oxylipins only detected in this group. Finally, oxylipins that were higher in infected snails induced naïve snails to increase their immune responses compared to sham-exposed snails. Our results provide evidence that snails exhibit DDP, and the changes in oxylipins emitted by infected hosts may be one of the molecular mechanisms driving this phenomenon.

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“…From infected first intermediate hosts, live cercariae were identified as echinostomes (Family Echinostomatidae) based on the presence of collar spines (Schell 1985). Using morphology alone, it can be difficult to identify echinostomes to species (Bolek et al 2019). Thus, we sequenced the DNA from a subset of parasites at the NADH dehydrogenase 1 (ND1) gene in a Containment Level II lab (Facility Certification #BF0172-2R).…”

Section: Introductionmentioning

confidence: 99%

Parasite-modified behaviour in non-trophic transmission: trematode parasitism increases the attraction between snail intermediate hosts

et al. 2020

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J.T. Detwiler). Parasite-modified behaviour in non-trophic transmission: Trematode parasitism increases the attraction between snail intermediate hosts Many parasites with complex life cycles cause host behavioral changes that increase the likelihood of transmission to the next host. Parasite modification is often found in trophic transmission, but its influence on non-trophic transmission is unclear. In trematodes, transmission from the first to second intermediate host is non-trophic suggesting that free-swimming larvae (cercariae) emerging in closer proximity to the next host would have higher transmission success. We performed a series of behavioral experiments with echinostome trematodes and their snail hosts to determine if potential second hosts (Planorbella sp.) were more attracted to parasitized first hosts (Lymnaea elodes Say, 1821). In a Y-maze, a responding snail (Planorbella Haldeman, 1842 sp.) was placed in the base and its response to five treatments was assessed: no stimulus, duckweed (a food item, Lemna turionifera Landolt), non-parasitized L. elodes, parasitized L. elodes, and finally parasitized versus non-parasitized L. elodes. Snails showed some attraction to uninfected snails, but had a stronger response to infected first host snails. These results indicate that potential second host snails were more attracted to parasitized, heterospecific first host snails over non-parasitized heterospecific snails. This study demonstrates that echinostome trematodes alter snail behaviour by changing navigational choices in uninfected potential hosts through a chemical communication mechanism. Many trematode species cause behavioural changes in their intermediate hosts, which makes the transmission of the larval parasites to the next host more likely (Moore 1984; Cézilly et al. 2010; Lafferty and Shaw 2013). Most studies of trematode-altered behaviour have demonstrated its importance in trophic transmission whereby second intermediate hosts are consumed by definitive hosts (Lafferty and Shaw 2013). In these cases, second intermediate hosts, infected with encysted parasites (metacercariae), behavein ways that make predation and thus consumption of parasites by the next host in the life cycle more likely. For example, brain-encysting metacercariae cause ants to change their activity and microhabitat choice by freezing on the top of a blade of grass, making predation by grazing ungulate hosts more likely (Moore 1984). Likewise, fish infected with metacercariae behaved more conspicuously and were more likely to be eaten by bird hosts (Lafferty and Morris 1996). ). We used parasitized L. elodes as first intermediate hosts, and non-parasitized Planorbella sp. snails as potential second intermediate hosts to test whether parasitemodified behaviour affected heterospecific snail interactions. We hypothesized that if parasites modify host interactions, then uninfected Planorbella sp. snails would be more attracted to parasitized L. elodes first intermediate host snails compared to uninfected L. elodes.

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Selected Wildlife Trematodes

Cited by 12 publications

References 153 publications

Research on helminths from Mexican amphibians: gaps, trends, and biases

Research on helminths from Mexican amphibians: gaps, trends, and biases

Density-Dependent Prophylaxis in Freshwater Snails Driven by Oxylipin Chemical Cues

Parasite-modified behaviour in non-trophic transmission: trematode parasitism increases the attraction between snail intermediate hosts

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