Selection of the Host's Habitat by Cercariae: From Laboratory Experiments to the Field

Haas, Wilfried; Beran, Bernadett; Loy, Christina

doi:10.1645/ge-1192.1

Cited by 30 publications

(26 citation statements)

References 19 publications

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“…The transmission success of cercariae depends mainly on accidental contact with the host. In general, trematode cercariae can actively move toward their host’s surface only over a few millimeters [39]. Fish ventilation activity producing directional water flow towards the gills provides parasites with a powerful mechanism of transportation in a viscous media.…”

Section: Discussionmentioning

confidence: 99%

Increased ventilation by fish leads to a higher risk of parasitism

Mikheev

Pasternak

Valtonen

et al. 2014

Parasites & Vectors

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BackgroundFish are common intermediate hosts of trematode cercariae and their gills can potentially serve as important sites of penetration by these larval stages. We experimentally tested the hypothesis that volume of ventilation flow across the gills contributes to acquisition of these parasites by fish. We manipulated the intensity of ventilation by using different oxygen concentrations.MethodsJuvenile Oncorhynchus mykiss were individually exposed for 10 minutes to a standard dose of Diplostomum pseudospathaceum cercariae at three levels of oxygen concentration, 30, 60 and 90%. Ventilation amplitude (measured as a distance between left and right operculum), operculum beat rate, and the number of cercariae established in the eyes of fish were recorded.ResultsFish reacted to low oxygen concentration with wider expansion of opercula (but not with increasing beat rate), leading to an increase in ventilation volume. As expected, the intensity of infection increased with decreasing oxygen saturation—probably due to a higher exposure to cercariae caused by increased ventilation under low oxygen concentrations. The number of cercariae acquired by an individual fish was positively correlated with ventilation amplitude and with ventilation volume, but not with operculum beat rate. However, even though the infection rate increased under these circumstances, the proportion of larval trematodes successfully establishing in fish eyes decreased with increasing ventilation volume, suggesting that the high flow velocity, although increasing host exposure to cercarial parasites, may interfere with the ability of these parasites to penetrate their hosts. There was no difference in the behaviour of trematode cercariae exposed to low and high oxygen concentrations.ConclusionA reduction in oxygen saturation resulted in an increase in ventilation volume across the gills and in doing so an increase in the exposure of fish to cercariae. A significant correlation between ventilation volume and parasitism represents the first experimental evidence that this physiological mechanism generates variation in transmission of parasites to fish hosts. Other factors that modify ventilation flow, e.g. physiological or social stressors, are expected to produce similar effects on the transmission success of the parasites penetrating fish hosts using the gills.

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Section: Discussionmentioning

confidence: 99%

Increased ventilation by fish leads to a higher risk of parasitism

Mikheev

Pasternak

Valtonen

et al. 2014

Parasites & Vectors

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“…Taking into account the fact that, after leaving the first host, E. spiniferum cercariae enter subsequent snails, where they transform into metacercariae, staying in the habitat preferred by uninfected individuals increases the success of their transmission. Haas et al (2008) emphasised the selective ability of parasites with regard to the habitat of the host. However, attention should be paid to the fact that infectivity of echinocercariae of different species is higher at warm than at cool temperatures (Evans, 1985;Shmidt and Fried, 1994;Koprivnikal et al, 2006;_ Zbikowski and _ Zbikowska 2009).…”

Section: Discussionmentioning

confidence: 99%

Symptoms of behavioural anapyrexia – Reverse fever as a defence response of snails to fluke invasion

Żbikowska¹,

Cichy²

2012

Journal of Invertebrate Pathology

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“…2c). Behaviour of this kind reduces the chance of super infection of the first intermediate host and ensure a wider distribution of infected second intermediate hosts (Haas et al, 2008), increasing the likelihood of transmission to the definitive vertebrate host by predation.…”

Section: Population Dynamics Of Cercariaementioning

confidence: 99%

Cercariae (Platyhelminthes: Trematoda) as neglected components of zooplankton communities in freshwater habitats

Morley

2012

Hydrobiologia

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Zooplanktonic animals live in the open water of freshwater habitats, whilst trematodes are ubiquitous parasitic worms of aquatic vertebrates and invertebrates. A defining characteristic of trematode life cycles is the cercariae, a mainly planktonic freeliving larval stage that emerges into the aquatic environment from infected molluscan hosts. Cercariae are lecithotrophic (non-feeding) larvae analogous of meroplankton. Although millions of planktonic cercariae enter freshwater habitats on a daily basis and are capable of forming into dense clouds, they are a largely neglected component of the zooplankton community, rarely mentioned in faunal studies. Nevertheless, there is increasing evidence to suggest that cercariae have important secondary roles in aquatic food webs and energy transfer. This article reacquaints freshwater biologists with cercariae, highlighting the key characteristics of their biology and population dynamics, their role in food webs, public health and veterinary importance, and the risk of increased population densities under the influence of climate change. The reasons for their neglect in freshwater biology is evaluated and considered to be associated with zooplankton sampling methodologies being unsuitable for collecting cercariae and the paucity of identification keys in the limnological literature.

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Selection of the Host's Habitat by Cercariae: From Laboratory Experiments to the Field

Cited by 30 publications

References 19 publications

Increased ventilation by fish leads to a higher risk of parasitism

Increased ventilation by fish leads to a higher risk of parasitism

Symptoms of behavioural anapyrexia – Reverse fever as a defence response of snails to fluke invasion

Cercariae (Platyhelminthes: Trematoda) as neglected components of zooplankton communities in freshwater habitats

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