Potential negative effects and heterogeneous distribution of a parasitic copepod Salmincola edwardsii (Copepoda: Lernaeopodidae) on Southern Asian Dolly Varden Salvelinus curilus in Hokkaido, Japan

Hasegawa, Ryota; Ayer, Christopher G.; Umatani, Yoshiyuki; Miura, Kazuki; Ukumura, Miyo; Katahira, Hirotaka; Koizumi, Itsuro

doi:10.1016/j.parint.2021.102529

Cited by 9 publications

(7 citation statements)

References 48 publications

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“…2017), 99.69% identity with a specimen from Norway (Tjensvoll 2005), and 99.57% identity with specimens from Japan (Hasegawa et al. 2022a). Levels of intraspecific COI variation within S. edwardsii , including both the Fort McCoy and New York populations (mean = 0.011, SD = 0.006; range = 0.002–0.020), and interspecific variation between S. edwardsii and congeners (mean = 0.138, SD = 0.027; range = 0.091–0.173) were similar to levels observed within (mean = 0.007, SD = 0.005; range = 0.002–0.017) and among other Salmincola species (mean = 0.156, SD = 0.013; range = 0.130–0.156), respectively (Figure 2).…”

Section: Resultsmentioning

confidence: 99%

Molecular identification and environmental DNA detection of gill lice ectoparasites associated with Brook Trout declines

Katz,

Tetzlaff,

Johnson

et al. 2023

Trans Am Fish Soc

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ObjectiveGill lice Salmincola spp. are among the most widely reported parasites of freshwater salmonids and have been associated with recent declines in native Brook Trout Salvelinus fontinalis populations. Effective gill lice surveillance is vital for salmonid conservation success, but current survey approaches are often inadequate or problematic. We developed an environmental DNA (eDNA)‐based approach to detect the gill louse Salmincola edwardsii and explored the viability of this approach as a management tool for rapid, large‐scale gill lice surveillance at Fort McCoy, Wisconsin, USA.MethodsReference sequences were generated from gill lice specimens collected at Fort McCoy to confirm their identify as S. edwardsii and used to design a quantitative polymerase chain reaction (qPCR) assay that targets S. edwardsii mitochondrial cytochrome c oxidase I (COI). Assay validation included in silico and in vitro sensitivity and nontarget specificity testing, and assay performance was validated in situ by sampling eDNA at sites characterized via electrofishing.ResultMolecular analysis of reference sequences confirmed S. edwardsii identity while also providing the first multi‐population assessment of genetic variation for North American Salmincola and the most taxonomically comprehensive molecular phylogeny of Lernaeopodidae to date. Salmincola edwardsii eDNA was detected at 14 of 38 sites, including 12 of 14 sites with known active infestations, with no evidence that the odds of detecting gill lice via electrofishing was greater than the odds of detections from eDNA analysis. Brook Trout presence was highly predictive of gill lice eDNA site occupancy, concordant with S. edwardsii being an obligate parasite of Salvelinus fishes. However, by expanding survey coverage via eDNA analysis, we were able to identify an isolated drainage with Brook Trout where S. edwardsii is apparently absent, confirming electrofishing observations.ConclusionThese results suggest that eDNA analysis is equivalent to electrofishing for detecting gill lice in terms of performance yet offers substantial gains in survey efficiency. Further, this study demonstrates how eDNA analysis can provide valuable intel for directing management efforts, especially when used to expand survey coverage and prioritize follow‐up conventional surveys to assess host–parasite abundance, demographics, and status.

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Section: Resultsmentioning

confidence: 99%

Molecular identification and environmental DNA detection of gill lice ectoparasites associated with Brook Trout declines

Katz,

Tetzlaff,

Johnson

et al. 2023

Trans Am Fish Soc

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show abstract

“…Although many studies have pointed out the negative impacts of parasites on wild host populations, most reported simple correlations and hence overlooked causal relationships (Harper et al ., 1999;Vicenteet al, 2004;Sala-Bozano et al, 2012;Hasegawa et al, 2022a). This is probably due to methodological difficulties in the long-term tracking of host individual and parasite infections.…”

Section: Discussionmentioning

confidence: 99%

“…How did the copepods in our study cause positive feedback?Salmincola spp. cause tissue damage, such as gill destructions and mouth cavity swellings (Kabata & Cousens, 1977;Nagasawa et al, 1998;Hasegawa et al, 2022a). These infections also induce the immune response of hosts (Hiramatsu et al ., 2001).…”

Section: Discussionmentioning

confidence: 99%

“…These infections also induce the immune response of hosts (Hiramatsu et al ., 2001). Beyond developing immune systems, repairing damaged tissues also requires much energy (White et al, 2020), eventually leading to loss of host body condition (Hasegawa et al, 2022a). Physical attachment itself could induce body condition loss.…”

Section: Discussionmentioning

confidence: 99%

“…However, most field studies have only examined cross-sectional correlations and have discussed one-sided causalities (Beldomenicoet al ., 2008). Field studies suggest a negative correlation between host body condition, and infection parameters generally indicate that parasites are causes of poor host condition (Harper et al ., 1999;Vicente et al, 2004;Sala-Bozano et al, 2012;Hasegawa et al, 2022a), although some showed poor condition situations such as food limitations may increase parasite prevalence and intensity because hosts compromise their immune functions under such situations (Forbes et al, 2016). Most importantly, when parasite infections are both the cause and consequence of a poor host condition, we can also expect positive feedback: an infected host with a poor body condition due to the parasite infection will be more susceptible to further infection (Beldomenico et al, 2008;Beldomenico et al, 2009 a, b;.…”

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Disentangling the causality between parasite infections and poor host conditions in the wild population

Hasegawa

Otsuki

Uemura

et al. 2023

Preprint

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Although parasites reduce host health, parasite infections also occur as a consequence of compromised host health. Both causalities could induce positive feedback, in which infected hosts with poor body conditions may suffer further infection, but it has rarely been demonstrated in the wild, possibly due to methodological difficulties. We used a mark-recapture survey combined with structural equation modelling (SEM) to examine whether both causalities and positive feedback occurred in stream salmonid and parasitic copepod systems. We found that parasitic copepods reduced host conditions and hosts with poor conditions were likely to be infected, suggesting that positive feedback can occur in the wild. Importantly, heavily infected hosts with poor body conditions showed lower apparent survival rates. Our findings provide robust evidence showing host condition–parasite infection dynamics, offering novel insights into how positive feedback could strongly undermine the wild host population via reduction of host survival.

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Comparison of qPCR and metabarcoding for environmental DNA surveillance of a freshwater parasite

Johnson,

Tetzlaff,

Katz

et al. 2024

Ecology and Evolution

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Analysis of environmental DNA (eDNA) has been successfully used across freshwater ecological parasitology to inform management of ecologically and economically important species. However, most studies have used species‐specific quantitative polymerase chain reaction (qPCR) assays to detect target taxa. While generally effective, this approach limits the amount of community and management‐supporting data that can be obtained from eDNA samples. If eDNA metabarcoding could be conducted with the same accuracy of a single species approach, researchers could simultaneously detect a target species while obtaining vast community data from eDNA samples. We sampled 38 freshwater sites on Fort McCoy, Wisconsin and compared qPCR to metabarcoding for eDNA detection of the ectoparasitic gill louse Salmincola edwardsii, an obligate parasite of Salvelinus fishes (chars). We found no evidence to suggest S. edwardsii occupancy or detection probabilities differed between qPCR and metabarcoding. Further, we found that the number of S. edwardsii reads from metabarcoding were negatively predictive of CT values from qPCR (CT value indicates cycle a significant amount of target eDNA is detected, with lower CTs indicative of more DNA), demonstrating that our metabarcoding reads positively predicted qPCR DNA quantities. However, the number of reads was not predictive of overall qPCR score (number of positive qPCR replicates). In addition to S. edwardsii, metabarcoding led to the detection of a vast community of over 2600 invertebrate taxa. We underscore the necessity for conducting similar analyses across environments and target species, as the ecology of eDNA will vary on a per‐study basis. Our results suggest that eDNA metabarcoding provides a highly sensitive and accurate method for detecting parasitic gill lice while also illuminating the broader biological community and co‐occurrence of species in the environment.

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Potential negative effects and heterogeneous distribution of a parasitic copepod Salmincola edwardsii (Copepoda: Lernaeopodidae) on Southern Asian Dolly Varden Salvelinus curilus in Hokkaido, Japan

Cited by 9 publications

References 48 publications

Molecular identification and environmental DNA detection of gill lice ectoparasites associated with Brook Trout declines

Molecular identification and environmental DNA detection of gill lice ectoparasites associated with Brook Trout declines

Disentangling the causality between parasite infections and poor host conditions in the wild population

Comparison of qPCR and metabarcoding for environmental DNA surveillance of a freshwater parasite

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