Long‐term datasets are needed to evaluate temporal patterns in wildlife disease burdens, but historical data on parasite abundance are extremely rare. For more than a century, natural history collections have been accumulating fluid‐preserved specimens, which should contain the parasites infecting the host at the time of its preservation. However, before this unique data source can be exploited, we must identify the artifacts that are introduced by the preservation process. Here, we experimentally address whether the preservation process alters the degree to which metazoan parasites are detectable in fluid‐preserved fish specimens when using visual parasite detection techniques. We randomly assigned fish of three species (
- PAR ID:
- 10422424
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 120
- Issue:
- 3
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Gadus chalcogrammus, Thaleichthys pacificus, and Parophrys vetulus ) to two treatments. In the first treatment, fish were preserved according to the standard procedures used in ichthyological collections. Immediately after the fluid‐preservation process was complete, we performed parasitological dissection on those specimens. The second treatment was a control, in which fish were dissected without being subjected to the fluid‐preservation process. We compared parasite abundance between the two treatments. Across 298 fish individuals and 59 host–parasite pairs, we found few differences between treatments, with 24 of 27 host–parasite pairs equally abundant between the two treatments. Of these, one pair was significantly more abundant in the preservation treatment than in the control group, and two pairs were significantly less abundant in the preservation treatment than in the control group. Our data suggest that the fluid‐preservation process does not have a substantial effect on the detectability of metazoan parasites. This study addresses only the effects of the fixation and preservation process; long‐term experiments are needed to address whether parasite detectability remains unchanged in the months, years, and decades of storage following preservation. If so, ecologists will be able to reconstruct novel, long‐term datasets on parasite diversity and abundance over the past century or more using fluid‐preserved specimens from natural history collections. -
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Historical data are extremely rare but essential for ascertaining whether contemporary infectious disease burdens are unusual. Natural history collections are a valuable source of such data, especially for reconstructing long timelines of parasite abundance. We quantified the parasites of 109 museum specimens of English sole (
Parophrys vetulus ), an economically important flatfish, collected from Puget Sound, Washington, over a 90‐year period (1930–2019). We counted nearly 2,500 individual parasites representing 23 distinct species/morphotypes and four broad taxonomic groupings. Of the 12 taxa that were prevalent enough to include in the analysis, nine did not change in abundance over time, two (an acanthocephalan and a trematode) decreased, and one (another trematode) increased. By broad taxonomic grouping, nematodes, trematodes, and leeches exhibited no change over time, whereas acanthocephalans declined significantly. The diverging patterns among parasite taxa suggest a double‐edged sword of responses to long‐term ocean change: some parasites might be on the rise, while others are declining. -
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Abstract Habitat loss and fragmentation are likely to seriously impact parasites, a less studied but critical component of ecosystems, yet we lack long‐term experimental evidence. Parasites structure communities, increase connectivity in food webs, and account for a large proportion of an ecosystem's total biomass. Food web models predict that parasites with multiple obligate hosts are at greater risk of extinction because the local extinction, or reduction in abundance, of any host will result in a life‐cycle bottleneck for the parasite. We examine the response of a parasite and its multiple hosts to forest fragmentation over 26 years in the Wog Wog Habitat Fragmentation Experiment in southeastern Australia. The parasite is the nematode
Hedruris wogwogensis , its intermediate host is the amphipod,Arcitalitrus sylvaticus , and its definitive host is the skink,Lampropholis guichenoti . In the first decade after fragmentation, nematodes completely disappeared from the matrix (plantation forestry) and all but disappeared from their definitive host (skinks) in fragments, and by the third decade after fragmentation had not appreciably recovered anywhere in the fragmented landscape compared to continuous forest. The low prevalence of the nematode in the fragmented landscape was associated with the low abundance of one or the other host in different decades: low abundance of the intermediate host (amphipod) in the first decade and low abundance of the definitive host (skink) in the third decade. In turn, the low abundance of each host was associated with changes to the abiotic environment over time due largely to the dynamically changing matrix as the plantation trees grew. Our study provides rare long‐term experimental evidence of how disturbance can cause local extinction in parasites with life cycles dependent on more than one host species through population bottlenecks at any life stage. Mismatches in the abundance of multiple hosts over time are likely to be common following disturbance, thus causing parasites with complex life cycles to be particularly susceptible to habitat fragmentation and other disturbances. The integrity of food webs, communities, and ecosystems in fragmented landscapes may be more compromised than presently appreciated due to the sensitivity of parasites to habitat fragmentation. -
Habitat isolation and disturbance are important regulators of biodiversity, yet it remains unclear how these environmental features drive differences in parasite diversity between ecosystems. We test whether the biological communities in an isolated, frequently disturbed marine ecosystem (deep-sea hydrothermal vents) have reduced parasite richness and relatively fewer parasite species with indirect life cycles (ILCs) compared to ecosystems that are less isolated and less disturbed. We surveyed the parasite fauna of the biological community at the 9°50′N hydrothermal vent field on the East Pacific Rise and compared it to similar datasets from a well-connected and moderately disturbed ecosystem (kelp forest) and an isolated and undisturbed ecosystem (atoll sandflat). Parasite richness within host species did not differ significantly between ecosystems, yet total parasite richness in the vent community was much lower due to the low number of predatory fish species. Contrary to expectation, the proportion of ILC parasite species was not lower at vents due to a high richness of trematodes, while other ILC parasite taxa were scarce (nematodes) or absent (cestodes). These results demonstrate the success of diverse parasite taxa in an extreme environment and reinforce the importance of host diversity and food web complexity in governing parasite diversity.more » « less
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Abstract Species invasion and redistribution, driven by climate change and other anthropogenic influences, alter global biodiversity patterns and disrupt ecosystems. As host species move, they can bring their associated parasites with them, potentially infecting resident species, or leave their parasites behind, enhancing their competitive ability in their new ranges. General rules to predict why invading hosts will retain some parasites but not others are relatively unexplored, and the potential predictors are numerous, ranging from parasite life history to host community composition.
In this study, we focus on the parasite retention process during host invasion. We used the Global Mammal Parasite Database to identify terrestrial mammal hosts sampled for parasites in both native and non‐native ranges. We then selected predictors likely to play a role in parasite retention, such as parasite type, parasite specialism, species composition of the invaded community, and the invading host's phylogenetic or trait‐based similarity to the new community.
We modelled parasite retention using boosted regression trees, with a suite of 25 predictors describing parasite and host community traits. We further tested the generality of our predictions by cross‐validating models on data for other hosts and invasion locations.
Our results show that parasite retention is nonrandom and predictable across hosts and invasions. It is broadly shaped by parasite type and parasite specialism, with more specialist parasites that infect many closely related hosts more likely to be retained. This trend is pronounced across parasite types; helminths, however, show a more uniform likelihood of retention regardless of specificity.
Overall, we see that most parasites are not retained (11% retained), meaning many invasive species may benefit from enemy release. However, species redistribution does have the potential to spread parasites, and this also has great relevance to understanding conservation implications of species invasions. We see that specialist parasites are most likely to coinvade with their hosts, which suggests that species closely related to the invasive hosts are most likely to be affected by parasite spillover.
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2211903120
