Relationship between European eel<i>Anguilla anguilla</i>infection with non‐native parasites and swimming behaviour on encountering accelerating flow

Newbold, L.R.; Hockley, Frances Anne; Williams, C.; Cable, Joanne; Reading, A. J.; Auchterlonie, Neil Alexander; Kemp, Paul S.

doi:10.1111/jfb.12659

Cited by 25 publications

(23 citation statements)

References 68 publications

(125 reference statements)

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“…However, increased stress and mortality have been reported in parasitized European eels that experienced periods of hypoxia (Gollock, Kennedy, & Brown, 2005;Lefebvre, Contournet, & Crivelli, 2007;Molnár, Székely, & Baska, 1991), indicating a cumulative negative effect from multiple stressors. Natural and experimental A. crassus infections impair swim bladder function (Würtz, Taraschewski, & Pelster, 1996), and laboratory swimming trials indicated that natural infections increase energy consumption and alter swimming behavior of the European eel and may thus interfere with the spawning migration and reproduction (Newbold et al, 2015;Palstra, Heppener, Ginneken, Székely, & Thillart, 2007;Pelster, 2015;Würtz et al, 1996). For the Japanese eel, body condition was not affected by A. crassus infections (Han et al, 2008).…”

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confidence: 99%

Gene expression response to a nematode parasite in novel and native eel hosts

Bracamonte

Johnston

Monaghan

et al. 2019

Ecology and Evolution

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Invasive parasites are involved in population declines of new host species worldwide. The high susceptibilities observed in many novel hosts have been attributed to the lack of protective immunity to the parasites which native hosts acquired during their shared evolution. We experimentally infected Japanese eels (Anguilla japonica) and European eels (Anguilla anguilla) with Anguillicola crassus, a nematode parasite that is native to the Japanese eel and invasive in the European eel. We inferred gene expression changes in head kidney tissue from both species, using RNA‐seq data to determine the responses at two time points during the early stages of infection (3 and 23 days postinfection). At both time points, the novel host modified the expression of a larger and functionally more diverse set of genes than the native host. Strikingly, the native host regulated immune gene expression only at the earlier time point and to a small extent while the novel host regulated these genes at both time points. A low number of differentially expressed immune genes, especially in the native host, suggest that a systemic immune response was of minor importance during the early stages of infection. Transcript abundance of genes involved in cell respiration was reduced in the novel host which may affect its ability to cope with harsh conditions and energetically demanding activities. The observed gene expression changes in response to a novel parasite that we observed in a fish follow a general pattern observed in amphibians and mammals, and suggest that the disruption of physiological processes, rather than the absence of an immediate immune response, is responsible for the higher susceptibility of the novel host.

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confidence: 99%

Gene expression response to a nematode parasite in novel and native eel hosts

Bracamonte

Johnston

Monaghan

et al. 2019

Ecology and Evolution

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“…Some authors have identified water temperature thresholds below which little or no migratory activity takes place (Euston et al, ); prolonged delays would result in silver eels encountering cooler temperatures and reduced day length, with the likelihood of delaying migration for a season. Parasite loading can also cause delays to downstream migration (Newbold et al, ). Prolonged delays can lead to reversion to yellow‐eel status and this has been recorded in silver A. anguilla in which seaward migration had been arrested (Durif et al, ).…”

Section: Discussionmentioning

confidence: 99%

Diel and seasonal movements of silver eels, Anguilla dieffenbachii, emigrating from a lake subject to hydro‐electric control

Jellyman

Unwin

2017

Journal of Fish Biology

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To investigate the behaviour and fate of silver female longfin eels Anguilla dieffenbachii in relation to flow variations from New Zealand's largest (700 MW) hydro-electric station, 210 A. dieffenbachii were tagged with acoustic transmitters during summer and autumn over 6 years from 2005 to 2010. A shoreline array of receivers (2005-2008) was supplemented by positioning systems near the power station and natural outlet (2009-2010) that enabled continuous tracking of A. dieffenbachii within these areas. Tagged A. dieffenbachii (total length 785-1372 mm) emigrated from the lake over an 8 month period, either in the same season they were tagged (75%) or the following spring after over-wintering for up to 7 months (25%). Most A. dieffenbachii (67%) emigrated via the natural outlet. Swimming activity was related to water temperature and was greatest during the summer months. Activity was strongly diel, although less so at the outlet where A. dieffenbachii migrating at depths greater than 20 m often did so during daylight. To analyse searching behaviour, sustained periods of continuous swimming activity (termed forays) were examined in the vicinity of the outlet. Most successful forays (where the A. dieffenbachii exited the lake via the lower Waiau River) were associated with outflows; such outflows were sometimes <10 m s although most successful forays took place at flows >50 m s The timing of successful forays was related to outflow, the day of year and whether the A. dieffenbachii had delayed migration or not, but not lunar phase or rainfall. Passage time from the lake to the lower Waiau River 81 km downstream decreased from an average of 58 days early in the season to <1 day in late autumn. The wide range of behaviours and responses displayed by female silver A. dieffenbachii were interpreted as an inherent form of bet-hedging to spread the risks associated with silvering and seaward migration in this slow-growing species.

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“…Infected eels commonly suffer from impaired swim bladder functioning (Würtz et al 1996;Würtz and Taraschewski 2000) and reduced swimming abilities (Palstra et al 2007;Newbold et al 2015), likely affecting the spawning migration (Pelster 2015). As a result, the parasite might have a strong effect on the viability of the European eel and variability at Electronic supplementary material The online version of this article (doi:10.1007/s12686-015-0501-z) contains supplementary material, which is available to authorized users.…”

Section: Introductionmentioning

confidence: 99%

Characterization of MHC class II genes in the critically endangered European eel (Anguilla anguilla)

Bracamonte

Baltazar‐Soares

Eizaguirre

2015

Conservation Genet Resour

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Many exploited fish species are threatened with collapse and the European eel is no exception. Its abundance has declined dramatically and various reasons account for this, among them the introduction of the invasive swim bladder nematode Anguillicola crassus. For developing an adequate immune response against this parasite, variation at the genes of the major histocompatibility complex (MHC), a key component of the adaptive immune system, might be essential and assessing their diversity might provide critical information for improving conservation strategies. Here, we characterized the MHC class II of the European eel. We provide evidence for relatively high diversity at both MHC IIA and MHC IIB, which contrasts with findings for other endangered species. Furthermore, both genes show signs of site-specific positive selection. The absence of overall positive selection at MHC IIB might, however, suggests that demographic shifts have negatively impacted that gene, thereby possibly reducing the adaptive potential of the European eel.

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Relationship between European eelAnguilla anguillainfection with non‐native parasites and swimming behaviour on encountering accelerating flow

Cited by 25 publications

References 68 publications

Gene expression response to a nematode parasite in novel and native eel hosts

Gene expression response to a nematode parasite in novel and native eel hosts

Diel and seasonal movements of silver eels, Anguilla dieffenbachii, emigrating from a lake subject to hydro‐electric control

Characterization of MHC class II genes in the critically endangered European eel (Anguilla anguilla)

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