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John W. Lewis - One of the best experts on this subject based on the ideXlab platform.
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Toxicity of cadmium and zinc to the cercarial activity of Diplostomum spathaceum (Trematoda: Diplostomidae)
2015Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:Abstract. The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 100 µg/l was investigated against the activity of Diplostomum spathaceum (Rudolphi, 1819) cercariae. Over a 24 h exposure period a significant reduction in cercarial activity occurred in solutions of cadmium, zinc, and a mixture of cadmium and zinc at all concentrations. Reduced cercarial activity also occurred in all toxicant solutions compared with controls after only 6 h exposure indicating that cercariae were vulnerable during the period of maximum cercarial infectivity (0–5 h). The mechanisms of metal toxicity and their importance to parasite transmission are discussed. Studies on the influence of toxic pollutants on parasites of aquatic organisms have increased in recent years with much focus on the pollutant effects on host-parasite interactions (Khan and Thulin 1991) and more recently on the free-living stages of parasites, especially the survival of digenean cercariae (e.g. Abd Allah et al. 1996, Soucek and Noblet 1998, Pietrock et al. 2001). However, most investigations have found that only lim-ited mortality occurs in the presence of low concentra
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Toxicity of cadmium and zinc mixtures to cercarial tail loss in Diplostomum spathaceum (Trematoda:Diplostomidae).
Ecotoxicology and environmental safety, 2005Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:Abstract The effects of cadmium and zinc mixtures on tail loss of the free-living cercarial stage of the parasitic fluke Diplostomum spathaceum were investigated at concentrations ranging from 0.1 to 10,000 μg/L. Cercariae were exposed to metal mixtures of equal concentrations, metal mixtures of unequal concentrations, and a low-dose pretreatment followed by high-dose exposure mixtures. Under control conditions as the cercarial population aged tail loss occurred naturally a few hours before death, with an increasing tail loss over time associated with a decrease in cercarial survival. Under all mixture exposures the period of tail loss was prolonged compared to single-metal exposures. In most test solutions this was associated with a similar increase in survival of cercariae. Inhibition of tail loss occurred in low concentrations (0.1–100 μg/L) of equal mixed exposures. In some unequal, and in all pretreatment mixture exposures, a significant stimulation of tail loss occurred compared to the pattern of decreasing survival over time within the cercarial population. The importance of toxic metal mixtures to cercarial tail loss and potential implications for successful parasite transmission are discussed.
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Changes in survival characteristics of Diplostomum spathaceum cercariae emerged from cadmium-exposed Lymnaea stagnalis.
Journal of helminthology, 2005Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:The effect of exposing Lymnaea stagnalis (Gastropoda: Pulmonata), infected with Diplostomum spathaceum (Trematoda: Diplostomatidae), to 100 microg l(-1) cadmium for 7 days on survival characteristics (survival, tail loss, decaudized cercarial life-span) of emerged cercariae was investigated. Exposure of L. stagnalis to cadmium resulted in significantly increased D. spathaceum cercarial survival and an inhibited tail loss compared to controls. The normal parallel relationship which exists over time between decreasing cercarial survival and increasing tail loss in controls was changed in cercariae from cadmium-exposed hosts with an increased proportion of cercarial deaths occurring without tail loss. The decaudized cercarial life-span over the survival period of the cercarial population did not significantly change. However comparisons between individuals decaudized during the initial 24 h time period with those which were decaudized during the final period of cercarial survival showed a significantly altered life span which did not occur in the control population. As a potential indicator of penetration 'fitness' comparisons were also undertaken between control and exposed cercariae decaudized during the initial 24 h time period, which revealed that the decaudized cercarial life-span from the exposed hosts was significantly different from controls. This may have important implications for the ability of cercariae to migrate through the tissues of their target host. The importance and relevance of these results to parasite transmission are discussed.
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Toxicity of cadmium and zinc mixtures to the decaudized cercarial life span of Diplostomum spathaceum
Journal of helminthology, 2005Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:The effects of cadmium and zinc mixtures at concentrations ranging from 0.1 to 10,000 microg l(-1) on the life-span of decaudized cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum (Trematoda: Diplostomatidae) was investigated. Cercariae were exposed to metal mixtures of equal and unequal concentrations, and a low-dose pre-treatment followed by a high-dose exposure mixtures. Metal mixtures demonstrated variable effects on decaudized cercariae either by increasing or reducing their life-span compared to single metal exposures dependent on concentration and the type of mixed metal treatment. Prolonged exposure to equal metal mixtures at low concentrations (0.1-100 microg l(-1)) resulted in a reduction in the life-span of decaudized cercariae at 0.1 and 100 microg l(-1) in those individuals decaudized during the initial 24 h exposure period compared with those decaudized during the final 24 h period of cercarial survival, whilst in controls there was no significant life-span change between the two time periods. Decaudized cercariae which were exposed to low concentrations (0.1-100 microg l(-1)) of equal metal mixtures were also evaluated for their role as an indicator of larval 'fitness' for migrating through the tissues of their target fish host for those individuals decaudized during the initial 24 h exposure period, and demonstrated only a limited change in their life-span compared to control and single metal exposures. The importance of metal mixtures in parasite establishment in the fish host is discussed.
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Toxicity of cadmium and zinc to the decaudised cercarial life-span of Diplostomum spathaceum (Trematoda: Diplostomidae).
Parasitology, 2003Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:SUMMARY The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 10 000 mg/l to the life-span of decaudised cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum was investigated. The effects of metal exposure at 3 temperatures (12, 20, and 25 xC) and 3 levels of water hardness (distilled water, soft water and hard water) were studied. In general, under most experimental conditions increasing metal concentrations reduced the life-span of decaudised cercariae. Increasing water hardness and decreasing water temperature caused an increase in the life-span of both control and metal exposed decaudised cercariae. However, at certain isolated metal concentrations, associated with a specific level of water hardness and temperature, increased survival above controls occurred. Differences in the relative toxicity of cadmium and zinc were dependent on the environmental conditions of exposure. The decaudised cercarial life-span under metal exposure was found to be generally independent of the overall cercarial survival and tail loss in most experimental conditions. Prolonged exposure to cadmium and zinc caused changes in the decaudised cercarial life-span when compared to individuals decaudised during the initial 24 h exposure period to those which were decaudised during the final 24 h period of cercarial survival. The validity of studying the decaudised cercarial life-span as an indicator of ‘ fitness ’ of larvae to migrate through the tissues of the target fish host, in terms of glycogen utilization, was assessed for those cercariae decaudised during the initial 24 h exposure period only. A limited reduction in the decaudised cercarial life-span during this period compared to controls was recorded, which may possibly indicate a reduced penetration ‘ fitness ’ of cercariae exposed to cadmium and zinc. The importance and relevance of these findings to parasite migration and establishment in the fish host are discussed.
Neil J. Morley - One of the best experts on this subject based on the ideXlab platform.
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Toxicity of cadmium and zinc to the cercarial activity of Diplostomum spathaceum (Trematoda: Diplostomidae)
2015Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:Abstract. The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 100 µg/l was investigated against the activity of Diplostomum spathaceum (Rudolphi, 1819) cercariae. Over a 24 h exposure period a significant reduction in cercarial activity occurred in solutions of cadmium, zinc, and a mixture of cadmium and zinc at all concentrations. Reduced cercarial activity also occurred in all toxicant solutions compared with controls after only 6 h exposure indicating that cercariae were vulnerable during the period of maximum cercarial infectivity (0–5 h). The mechanisms of metal toxicity and their importance to parasite transmission are discussed. Studies on the influence of toxic pollutants on parasites of aquatic organisms have increased in recent years with much focus on the pollutant effects on host-parasite interactions (Khan and Thulin 1991) and more recently on the free-living stages of parasites, especially the survival of digenean cercariae (e.g. Abd Allah et al. 1996, Soucek and Noblet 1998, Pietrock et al. 2001). However, most investigations have found that only lim-ited mortality occurs in the presence of low concentra
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Toxicity of cadmium and zinc mixtures to cercarial tail loss in Diplostomum spathaceum (Trematoda:Diplostomidae).
Ecotoxicology and environmental safety, 2005Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:Abstract The effects of cadmium and zinc mixtures on tail loss of the free-living cercarial stage of the parasitic fluke Diplostomum spathaceum were investigated at concentrations ranging from 0.1 to 10,000 μg/L. Cercariae were exposed to metal mixtures of equal concentrations, metal mixtures of unequal concentrations, and a low-dose pretreatment followed by high-dose exposure mixtures. Under control conditions as the cercarial population aged tail loss occurred naturally a few hours before death, with an increasing tail loss over time associated with a decrease in cercarial survival. Under all mixture exposures the period of tail loss was prolonged compared to single-metal exposures. In most test solutions this was associated with a similar increase in survival of cercariae. Inhibition of tail loss occurred in low concentrations (0.1–100 μg/L) of equal mixed exposures. In some unequal, and in all pretreatment mixture exposures, a significant stimulation of tail loss occurred compared to the pattern of decreasing survival over time within the cercarial population. The importance of toxic metal mixtures to cercarial tail loss and potential implications for successful parasite transmission are discussed.
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Changes in survival characteristics of Diplostomum spathaceum cercariae emerged from cadmium-exposed Lymnaea stagnalis.
Journal of helminthology, 2005Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:The effect of exposing Lymnaea stagnalis (Gastropoda: Pulmonata), infected with Diplostomum spathaceum (Trematoda: Diplostomatidae), to 100 microg l(-1) cadmium for 7 days on survival characteristics (survival, tail loss, decaudized cercarial life-span) of emerged cercariae was investigated. Exposure of L. stagnalis to cadmium resulted in significantly increased D. spathaceum cercarial survival and an inhibited tail loss compared to controls. The normal parallel relationship which exists over time between decreasing cercarial survival and increasing tail loss in controls was changed in cercariae from cadmium-exposed hosts with an increased proportion of cercarial deaths occurring without tail loss. The decaudized cercarial life-span over the survival period of the cercarial population did not significantly change. However comparisons between individuals decaudized during the initial 24 h time period with those which were decaudized during the final period of cercarial survival showed a significantly altered life span which did not occur in the control population. As a potential indicator of penetration 'fitness' comparisons were also undertaken between control and exposed cercariae decaudized during the initial 24 h time period, which revealed that the decaudized cercarial life-span from the exposed hosts was significantly different from controls. This may have important implications for the ability of cercariae to migrate through the tissues of their target host. The importance and relevance of these results to parasite transmission are discussed.
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Toxicity of cadmium and zinc mixtures to the decaudized cercarial life span of Diplostomum spathaceum
Journal of helminthology, 2005Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:The effects of cadmium and zinc mixtures at concentrations ranging from 0.1 to 10,000 microg l(-1) on the life-span of decaudized cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum (Trematoda: Diplostomatidae) was investigated. Cercariae were exposed to metal mixtures of equal and unequal concentrations, and a low-dose pre-treatment followed by a high-dose exposure mixtures. Metal mixtures demonstrated variable effects on decaudized cercariae either by increasing or reducing their life-span compared to single metal exposures dependent on concentration and the type of mixed metal treatment. Prolonged exposure to equal metal mixtures at low concentrations (0.1-100 microg l(-1)) resulted in a reduction in the life-span of decaudized cercariae at 0.1 and 100 microg l(-1) in those individuals decaudized during the initial 24 h exposure period compared with those decaudized during the final 24 h period of cercarial survival, whilst in controls there was no significant life-span change between the two time periods. Decaudized cercariae which were exposed to low concentrations (0.1-100 microg l(-1)) of equal metal mixtures were also evaluated for their role as an indicator of larval 'fitness' for migrating through the tissues of their target fish host for those individuals decaudized during the initial 24 h exposure period, and demonstrated only a limited change in their life-span compared to control and single metal exposures. The importance of metal mixtures in parasite establishment in the fish host is discussed.
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Toxicity of cadmium and zinc to the decaudised cercarial life-span of Diplostomum spathaceum (Trematoda: Diplostomidae).
Parasitology, 2003Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:SUMMARY The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 10 000 mg/l to the life-span of decaudised cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum was investigated. The effects of metal exposure at 3 temperatures (12, 20, and 25 xC) and 3 levels of water hardness (distilled water, soft water and hard water) were studied. In general, under most experimental conditions increasing metal concentrations reduced the life-span of decaudised cercariae. Increasing water hardness and decreasing water temperature caused an increase in the life-span of both control and metal exposed decaudised cercariae. However, at certain isolated metal concentrations, associated with a specific level of water hardness and temperature, increased survival above controls occurred. Differences in the relative toxicity of cadmium and zinc were dependent on the environmental conditions of exposure. The decaudised cercarial life-span under metal exposure was found to be generally independent of the overall cercarial survival and tail loss in most experimental conditions. Prolonged exposure to cadmium and zinc caused changes in the decaudised cercarial life-span when compared to individuals decaudised during the initial 24 h exposure period to those which were decaudised during the final 24 h period of cercarial survival. The validity of studying the decaudised cercarial life-span as an indicator of ‘ fitness ’ of larvae to migrate through the tissues of the target fish host, in terms of glycogen utilization, was assessed for those cercariae decaudised during the initial 24 h exposure period only. A limited reduction in the decaudised cercarial life-span during this period compared to controls was recorded, which may possibly indicate a reduced penetration ‘ fitness ’ of cercariae exposed to cadmium and zinc. The importance and relevance of these findings to parasite migration and establishment in the fish host are discussed.
E T Valtonen - One of the best experts on this subject based on the ideXlab platform.
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Parasite-induced aggression and impaired contest ability in a fish host
Parasites & vectors, 2010Co-Authors: V. N. Mikheev, Anna Pasternak, Jouni Taskinen, E T ValtonenAbstract:Background Success of trophically transmitted parasites depends to a great extent on their ability to manipulate their intermediate hosts in a way that makes them easier prey for target hosts. Parasite-induced behavioural changes are the most spectacular and diverse examples of manipulation. Most of the studies have been focused on individual behaviour of hosts including fish. We suggest that agonistic interactions and territoriality in fish hosts may affect their vulnerability to predators and thus the transmission efficiency of trophically transmitted parasites. The parasite Diplostomum spathaceum (Trematoda) and juvenile rainbow trout, Oncorhynchus mykiss, were used to study whether infection can alter aggression rates and territorial behaviour of intermediate fish hosts.
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Phenotypic Variation in Infectivity of Diplostomum spathaceum Cercariae Within a Population
The Journal of parasitology, 2007Co-Authors: Otto Seppala, Anssi Karvonen, E T ValtonenAbstract:The present study examined phenotypic variation in infectivity of Diplostomum spathaceum (Trematoda) cercariae within a natural population. Twelve infected Lymnaea stagnalis were collected from the field, and the infectivity of cercariae from individual snails was assessed under constant laboratory conditions. At a water temperature of 16.3 C, the mean infectivity of cercariae from the snails varied between 55.5% and 87.5%. Depending on the source of variation, this may have important ecological and evolutionary implications for both natural parasite populations and those occurring in aquaculture.
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Phenotypic Variation in Infectivity of Diplostomum spathaceum Cercariae Within a
2007Co-Authors: Otto Seppala, A Karvonen, E T ValtonenAbstract:The present study examined phenotypic variation in infec- tivity of Diplostomum spathaceum (Trematoda) cercariae within a nat- ural population. Twelve infected Lymnaea stagnalis were collected from the field, and the infectivity of cercariae from individual snails was assessed under constant laboratory conditions. At a water temperature of 16.3 C, the mean infectivity of cercariae from the snails varied be- tween 55.5% and 87.5%. Depending on the source of variation, this may have important ecological and evolutionary implications for both natural parasite populations and those occurring in aquaculture. In the present study, we examined within-population variation in the infectivity of Diplostomum spathaceum (Trematoda) cercariae by com- paring cercariae released by different field-collected host individuals under standardized laboratory conditions. We were particularly inter- ested in the level of variation in cercariae infectivity, but we also discuss possible causes and consequences of this variation. farm where they had been reared in indoor tanks supplied with ground water. This ensured that fish had no previous experience with D. spa- thaceum. We conducted the exposures by placing the fish individually into containers with 0.5 L of water (16.3 C) and 70 cercariae for 20 min. We used standardized laboratory conditions to prevent possible effects of environmental factors on the cercariae. Thus, cercariae infec- tivity reflected the variation caused only by parasite and snail charac- teristics. After the exposure, we maintained the fish in 185-L tank$ for 27 days. Although the parasite establishment in the eyes takes place very quickly, within 24 hr from exposure (Whyte et al., 1991), a longer maintenance period was used to allow parasite development and easy detection. Fish were maintained in large tanks because rainbow trout cannot be maintained in small containers for long periods. During the maintenance, water temperature decreased to 12.0 C, corresponding to ambient water temperature in nature during the study. We killed the! fish with an overdose of 0.01% MS 222 (Sigma Chemical Co., St. Louis, Missouri), measured the length (±1 mm) and mass (±0.1 g) of each fish, and counted the number of parasites in lenses by dissecting the eyes. We used the proportion of parasites that had successfully estab- lished the eye lenses as an estimate of parasite infectivity. The relation- ship between the number of cercariae released by each snail, and their infectivity, was not examined because cercariae release by D. spatha- ceum is highly variable (Karvonen, Kirsi et al., 2004). Thus, the short time period (4 hr) used in the experiment was unlikely to provide re- liable estimates of cercariae production. Eighteen fish of the total of 120 exposed to cercariae died during the maintenance period (0-4 individuals from fish exposed to cercariae from each snail) and were excluded from further analysis because their parasite abundances could not be measured reliably. The average (±SE) body length and mass of the fish were 76 ± 1.0 mm and 5.1 ± 0.2 g, respectively, and fish exposed to cercariae from different snails did not differ in size (analysis of variance (ANOVA): length: Fu = 1.232, P = 0.278; mass: Fu = 1.216, P = 0.288). Cercariae infectivity varied between different snail individuals (Kruskal-Wallis test: x2 = 28.749, P = 0.002; Fig. 1) because the mean proportion of parasites successfully establishing the lenses ranged between 55.5% and 87.5%. The average infectivity of the cercariae released by individual snails did not affect the number of fish that died during the maintenance period (linear re-
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Climate warming and disease risks in temperate regions--Argulus coregoni and Diplostomum spathaceum as case studies.
Journal of helminthology, 2006Co-Authors: T. Hakalahti, Anssi Karvonen, E T ValtonenAbstract:The link between climate changes and disease risks from various pathogens has been increasingly recognized. The effect of climatic factors on host-parasite population dynamics is particularly evident in northern latitudes where the occurrence and transmission of parasites are strongly regulated by seasonality-driven changes in environmental temperatures. Shortened winter periods would increase growth potential of many parasite populations. The ways in which climate warming could affect life history dynamics of the directly transmitted crustacean ectoparasite Argulus coregoni and complex life cycle trematode Diplostomum spathaceum, which frequently cause problems in northern fish farming, are discussed. Increased problems for fish farming are predicted in terms of increased infection pressure from these parasites in future. This would increase problems associated with infections and increase the use of expensive management protocols with high environmental impact.
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eye fluke induced cataract formation in fish quantitative analysis using an ophthalmological microscope
Parasitology, 2004Co-Authors: Anssi Karvonen, Otto Seppala, E T ValtonenAbstract:We examined the parasite-induced cataract formation in rainbow trout ( Oncorhynchus mykiss ) using slit-lamp microscopy to determine the relationship between cataract intensity and number of Diplostomum spathaceum parasites that were established in the lens. Cataract intensity increased significantly with parasite burden, but was also affected by the pattern of exposure to the parasite cercariae. The slit-lamp methodology proved useful in scoring the cataracts since it provides a 3-dimensional view into the lens and gives an actual picture of the location and intensity of the cataracts, which allows detailed investigations of mechanisms underlying cataract formation in various fish species. Potential applications of the method in fish farming and parasitological studies are discussed.
M. Crane - One of the best experts on this subject based on the ideXlab platform.
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Toxicity of cadmium and zinc to the cercarial activity of Diplostomum spathaceum (Trematoda: Diplostomidae)
2015Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:Abstract. The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 100 µg/l was investigated against the activity of Diplostomum spathaceum (Rudolphi, 1819) cercariae. Over a 24 h exposure period a significant reduction in cercarial activity occurred in solutions of cadmium, zinc, and a mixture of cadmium and zinc at all concentrations. Reduced cercarial activity also occurred in all toxicant solutions compared with controls after only 6 h exposure indicating that cercariae were vulnerable during the period of maximum cercarial infectivity (0–5 h). The mechanisms of metal toxicity and their importance to parasite transmission are discussed. Studies on the influence of toxic pollutants on parasites of aquatic organisms have increased in recent years with much focus on the pollutant effects on host-parasite interactions (Khan and Thulin 1991) and more recently on the free-living stages of parasites, especially the survival of digenean cercariae (e.g. Abd Allah et al. 1996, Soucek and Noblet 1998, Pietrock et al. 2001). However, most investigations have found that only lim-ited mortality occurs in the presence of low concentra
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Toxicity of cadmium and zinc mixtures to cercarial tail loss in Diplostomum spathaceum (Trematoda:Diplostomidae).
Ecotoxicology and environmental safety, 2005Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:Abstract The effects of cadmium and zinc mixtures on tail loss of the free-living cercarial stage of the parasitic fluke Diplostomum spathaceum were investigated at concentrations ranging from 0.1 to 10,000 μg/L. Cercariae were exposed to metal mixtures of equal concentrations, metal mixtures of unequal concentrations, and a low-dose pretreatment followed by high-dose exposure mixtures. Under control conditions as the cercarial population aged tail loss occurred naturally a few hours before death, with an increasing tail loss over time associated with a decrease in cercarial survival. Under all mixture exposures the period of tail loss was prolonged compared to single-metal exposures. In most test solutions this was associated with a similar increase in survival of cercariae. Inhibition of tail loss occurred in low concentrations (0.1–100 μg/L) of equal mixed exposures. In some unequal, and in all pretreatment mixture exposures, a significant stimulation of tail loss occurred compared to the pattern of decreasing survival over time within the cercarial population. The importance of toxic metal mixtures to cercarial tail loss and potential implications for successful parasite transmission are discussed.
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Toxicity of cadmium and zinc to the cercarial activity of Diplostomum spathaceum (Trematoda: Diplostomidae).
Folia parasitologica, 2003Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 100 µg/l was investigated against the activity of Diplostomum spathaceum (Rudolphi, 1819) cercariae. Over a 24 h exposure period a significant reduction in cercarial activity occurred in solutions of cadmium, zinc, and a mixture of cadmium and zinc at all concentrations. Reduced cercarial activity also occurred in all toxicant solutions compared with controls after only 6 h exposure indicating that cercariae were vulnerable during the period of maximum cercarial infectivity (0-5 h). The mechanisms of metal toxicity and their importance to parasite transmission are discussed.
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Toxicity of cadmium and zinc mixtures to Diplostomum spathaceum (Trematoda: Diplostomidae) cercarial survival.
Archives of environmental contamination and toxicology, 2002Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:The toxicity of cadmium and zinc mixtures at concentrations ranging from 0.1 to 10,000 μg/L was investigated against the survival of the free-living cercarial stage of the parasitic fluke Diplostomum spathaceum. Cercariae were exposed to metal mixtures of equal concentration, metal mixtures of unequal concentration, and low-dose pretreatment followed by high-dose exposure mixtures. Under all exposures cercarial survival was increased compared to that achieved with single metals. At exposures with metal mixture of equal concentration in the range 0.1–100 μg/L survival was increased compared to that achieved by controls. The mechanism of metal toxicity and their effects on cercarial survival are discussed.
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Toxicity of cadmium and zinc to Diplostomum spathaceum (Trematoda: Diplostomidae) cercarial survival.
International journal for parasitology, 2001Co-Authors: Neil J. Morley, M. Crane, John W. LewisAbstract:The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 10000 microg/l was investigated with cercariae of Diplostomum spathaceum at three temperatures (12, 20, 25 degrees C) and three levels of water hardness (distilled water, soft water, hard water). Under most environmental conditions survival of cercariae was reduced by increasing metal concentration. Increasing water hardness and decreasing water temperature caused an increase in the survival of both control and metal exposed cercariae. However, with decreasing temperature increased survival of metal-exposed cercariae above the control occurred at a number of low metal concentrations. Differences in the relative toxicity of cadmium and zinc to cercariae was dependent on the environmental conditions of exposure. The two heavy metals demonstrated little toxicity to cercariae during the period of maximum cercarial infectivity (0-5 h). The mechanisms of metal toxicity and their effects on cercarial survival are discussed.
P J Hudson - One of the best experts on this subject based on the ideXlab platform.
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Patterns of cercarial production from Diplostomum spathaceum: terminal investment or bet hedging?
Parasitology, 2004Co-Authors: A Karvonen, P J Hudson, S Kirsi, E T ValtonenAbstract:In the production of the infective cercariae of trematodes, the terminal investment hypothesis of life-history theory predicts that the rate of host exploitation and cercarial production should increase during the period of cercarial shedding since the reproductive value of the parasite decreases during this period. In contrast, a bet hedging hypothesis that focuses on the success of transmission when host contact rate is variable predicts that cercarial production should decrease in an attempt to keep the host alive for longer and thus would increase the probability of successful transmission. We examined these two hypotheses under laboratory conditions and recorded the production of Diplostomum spathaceum cercariae from naturally infected snail hosts, Lymnaea stagnalis. The average number of cercariae produced per day decreased as the snail host approached death counter to the terminal investment hypothesis. The finding supports the prediction of the bet hedging hypothesis and implies that the pattern of cercarial production may be explained by reduced virulence of the parasite within the snails to ensure extended total production time of cercariae. Nevertheless, survival of infected snails was still lower than uninfected snails suggesting that ultimately the infection still increased snail mortality rate. Cercarial production varied between days but was not cyclic, probably because of the physiology of the sporocysts within snails. Fewer cercariae were released at night, which may increase transmission efficiency to diurnally-active fish hosts. The mechanisms associated with daily cercarial production are discussed.
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Transmission, infectivity and survival of Diplostomum spathaceum cercariae.
Parasitology, 2003Co-Authors: A Karvonen, S Paukku, E T Valtonen, P J HudsonAbstract:SUMMARY The transmission dynamics of the cercariae of Diplostomum spathaceum were investigated under laboratory conditions using cercariae collected from naturally infected Lymnaea stagnalis. Cercariae were kept in a constant temperature of 20 xC and the survival and infectivity to naive young rainbow trout recorded at 3-h intervals until few cercariae were alive. Mortality initially remained constant but increased rapidly after 20 h. While a model of constant mortality fitted the survival data, an age-dependent model provided a better fit and implied that cercariae tended to carry similar quantities of resources and once these were exhausted the cercariae died. Cercarial infectivity also showed an age-dependent pattern although infectivity tended (P=0 . 09) to increase with age over the first 6 h of life and then fall. The per capita transmission rate of cercariae was investigated by experimentally infecting rainbow trout under standardized conditions, first with an increasing cercarial density and second, by keeping density constant but increasing numbers of cercariae. The per capita transmission rate was frequency dependent and averaged 0 . 341/h (i0 . 036).
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Transmission, infectivity and survival of Diplostomum spathaceum cercariae.
Parasitology, 2003Co-Authors: A Karvonen, S Paukku, E T Valtonen, P J HudsonAbstract:The transmission dynamics of the cercariae of Diplostomum spathaceum were investigated under laboratory conditions using cercariae collected from naturally infected Lymnaea stagnalis. Cercariae were kept in a constant temperature of 20 degrees C and the survival and infectivity to naïve young rainbow trout recorded at 3-h intervals until few cercariae were alive. Mortality initially remained constant but increased rapidly after 20 h. While a model of constant mortality fitted the survival data, an age-dependent model provided a better fit and implied that cercariae tended to carry similar quantities of resources and once these were exhausted the cercariae died. Cercarial infectivity also showed an age-dependent pattern although infectivity tended (P = 0.09) to increase with age over the first 6 h of life and then fall. The per capita transmission rate of cercariae was investigated by experimentally infecting rainbow trout under standardized conditions, first with an increasing cercarial density and second, by keeping density constant but increasing numbers of cercariae. The per capita transmission rate was frequency dependent and averaged 0.341/h (+/- 0.036).
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Transmission, infectivity and survival of Diplostomum spathaceum cercariae. Parasitology 127
2003Co-Authors: A Karvonen, S Paukku, E T Valtonen, P J HudsonAbstract:The transmission dynamics of the cercariae of Diplostomum spathaceum were investigated under laboratory conditions using cercariae collected from naturally infected Lymnaea stagnalis. Cercariae were kept in a constant temperature of 20 xC and the survival and infectivity to naïve young rainbow trout recorded at 3-h intervals until few cercariae were alive. Mortality initially remained constant but increased rapidly after 20 h. While a model of constant mortality fitted the survival data, an age-dependent model provided a better fit and implied that cercariae tended to carry similar quantities of resources and once these were exhausted the cercariae died. Cercarial infectivity also showed an age-dependent pattern although infectivity tended (P=0. 09) to increase with age over the first 6 h of life and then fall. The per capita transmission rate of cercariae was investigated by experimentally infecting rainbow trout under standardized conditions, first with an increasing cercarial density and second, by keeping density constant but increasing numbers of cercariae. The per capita transmission rate was frequency dependent and averaged 0. 341/h (¡0. 036)