Sperm production and sperm swimming speed, which most likely affect fertilization under sperm com... more Sperm production and sperm swimming speed, which most likely affect fertilization under sperm competition, are modified by proximate mechanisms. In a comprehensive observational study of free-living and reproductively active Arctic charr (Salvelinus alpinus), we examined the possible modulating effects of male social status (including ornamental development), parasite intensities, and immunity on novel traits indicative of ejaculate quality (e.g., Adenosine triphosphate (ATP) in sperm cells, levels of immunoglobulins attached to sperm cells, and the degree of DNA fragmentation in sperm cells). A multiple regression model showed no relationship between DNA fragmentation in sperm cells and abdominal coloration of charr, suggesting that sperm of colorful males are not better protected against oxidative stress. We found, however, that males with traits indicative of high social status had low amounts of ATP in sperm cells and also sperm cells with low swimming speed. Sperm production, on the other hand, was strongly predicted by parasite intensities only and these associations were mainly positive. Our results suggest that the presence of parasites seems to stimulate sperm production similar to what is observed among males entering subordinate reproductive roles. Thus, if resistance toward parasites is influencing parasite intensities, resistance may also indirectly be important for the "choice" of reproductive role and in turn investment in primary sex traits.
Immunity of parasites has been studied amazingly little, in spite of the fact that parasitic orga... more Immunity of parasites has been studied amazingly little, in spite of the fact that parasitic organisms, especially the arthropod parasites, need immunity to survive their own infections to successfully complete life cycles. Long-term effects of challenging environmental temperatures on immunity have remained unstudied in insects and parasites. Our study species, the deer ked (Lipoptena cervi; Linnaeus 1758), is an invasive, blood-feeding parasitic fly of cervids. Here, it was studied whether thermal stress during the pupal diapause stage could modify adult immunity (encapsulation capacity) in L. cervi. The effect of either a low temperature or high temperature peak, experienced during winter dormancy, on encapsulation response of active adult was tested. It was found that low temperature exposure during diapause, as long as the temperature is not too harsh, had a favourable effect on adult immunity. An abnormal, high temperature peak during pupal winter diapause significantly deteri...
According to the immunocompetence handicap hypothesis, males with attractive sexual ornamentation... more According to the immunocompetence handicap hypothesis, males with attractive sexual ornamentation are more handicapped than their less ornamented rivals because of the immunosuppressive androgens required for the production of secondary sexual characters. Here we studied the predictions of the hypothesis in a wild cyprinid fish, the roach (Rutilus rutilus). We assayed (1) sexual ornamentation (breeding tubercles), (2) circulating androgens (11-ketotestosterone
It has been suggested that human scent works as a signal in mate selection, but the empirical evi... more It has been suggested that human scent works as a signal in mate selection, but the empirical evidence is scarce. Here, we examined whether women's olfactory preferences for a man's scent could be correlated with his testosterone, estradiol, or cortisol concentrations, and whether these preferences change along with the menstrual cycle. In line with previous studies, women in their most fertile period gave the highest attractiveness ratings to all men. However, the intensity ratings by women at different menstrual phases did not significantly differ statistically. Interestingly, we found that cortisol concentration in saliva correlated positively with the attractiveness but not with the intensity ratings of male T-shirt odor by all women's groups. However, neither testosterone nor estradiol was significantly associated with the ratings of attractiveness or intensity. Thus, our study suggests that there could be a novel mechanism for odor-based selection in humans. D
Consistent individual differences in behavioural responses to perceived predation risk may have e... more Consistent individual differences in behavioural responses to perceived predation risk may have extensive ecological and evolutionary implications. We studied the repeatability of boldness across time and its relation to resource holding potential in the noble crayfish, Astacus astacus L., using predator-naïve immature individuals. We followed individual's shelter use both with and without exposure to the chemical and physical cues of predators, and with and without the presence of a conspecific. In addition, we examined if armament, i.e. relative chelae size, would be correlated with individual differences in behaviour. Individuals showed repeatable behaviours across time and context. Individuals that occupied the shelter in competitive dyadic tests also spent more time in the shelter during individual control observations, suggesting that boldness is a personality trait that does not necessarily relate positively to high resource holding potential in the noble crayfish. The relative size of chelae did not correlate with any of the measured behavioural variables. Our results suggest that boldness can be considered as individually consistent and ecologically important personality trait in the noble crayfish.
In contrast to females, tench Tinca tinca (L.) males have large pelvic fins with a thickened and ... more In contrast to females, tench Tinca tinca (L.) males have large pelvic fins with a thickened and bent second fin ray. Males also produce notable ventral protuberances during breeding, but the function of these male ornaments is not known. Using wild-caught fish, we found that both the size of pelvic fins and ventral protuberance were dependent on body mass/length ratio but not necessarily on condition. Plasma testosterone concentration and relative gonad mass were positively correlated with condition factor. Plasma testosterone concentration was not related to measures of non-specific immune function, but correlated positively with the size of pelvic fins corrected for body length. However, the studied male ornaments were not related to the measures of immune defence or to the load of Diplostomum spp. We did not find evidence for male-male dominance or female preference for large male characteristics within the natural variation in these traits. Thus, our study suggests that also other mechanisms than sexual selection on good genes might contribute to the maintenance of sexual dimorphism in tench.
ABSTRACT Seasonality in the immune defence of invertebrates can coincide with environmental varia... more ABSTRACT Seasonality in the immune defence of invertebrates can coincide with environmental variation but whether it is endogenously regulated, via biological clocks, or affected by previous immune challenges remains unclear. Using the native noble crayfish (Astacus astacus) held under constant laboratory conditions for a year, we explored (1) potential endogenous seasonal variation in immune defence, i.e. the encapsulation response, (2) the potential positive effect of repeated challenges with a standardized immune insult in subsequent seasons, i.e. long-lasting immune priming, and (3) whether long-lasting immune priming is dependent on endogenous seasonality. Independent measurements of the encapsulation response in different seasons revealed significant variation and a decrease in autumn. This result indicates previously undetected endogenous seasonal variation in invertebrate immunity. The weaker immune defence observed in autumn, i.e. the reproductive season of crayfish, might be caused by a circannual clock. When corrected for endogenous seasonality, we found no evidence for long-lasting immune priming.
Animals are often individually consistent in their behavior, not only over time, but also across ... more Animals are often individually consistent in their behavior, not only over time, but also across different functional contexts. Recent research has focused on phenotypic and evolutionary mechanisms explaining such personality differences through selection. Parasitism and predation induce important mortality and fitness costs, and are thus main candidates to create and maintain personality differences in the wild. Here, we present data on the behavioral consistency of the Eurasian minnow (Phoxinus phoxinus) from two populations that live in different tributaries of the same river, but whose ecological environment differs fundamentally with regard to predation and parasitism. We experimentally demonstrate that individual minnow in both study populations are consistent in their boldness and activity. However, the two study populations differ notably: in the high predation and parasitism risk population fish show higher mean boldness, but tend to be less active than fish in low predation and parasitism risk population. Parasite (Diplostomum phoxini) load was negatively, but not statistically significantly, associated with fish activity level. Our study suggests that parasitism and predation are likely important agents in the ecology and evolution of animal personalities.
Predation is often considered an important factor for population regulation and in some cases for... more Predation is often considered an important factor for population regulation and in some cases for the invasion success of prey. Small mammalian predation may be a major force in the population regulation of many ground-dwelling invertebrate species. The deer ked (Lipoptena cervi (L., 1758)) is an ectoparasitic fly of cervids. The species has a large distribution area and it has relatively rapidly spread in northern Europe during the previous four decades. The factors possibly regulating the distribution and invasion of this fly are poorly known. During the off-host stage of several months, pupae of deer ked are likely exposed to many ground-dwelling predators. To study whether small mammals would feed on deer keds, we conducted experiments by serving pupae of deer ked to wild-captured common shrews (Sorex araneus L., 1758), bank voles (Myodes glareolus (Schreber, 1780)), field voles (Microtus agrestis (L., 1761)), and semi-wild bank voles, and assessed pupal survival. As a control, we provided alternative food including common nutrients used by small mammals in their natural habitats. The results show that variable amounts of pupae of deer ked are consumed by all small-mammal species studied. Surprisingly, insectivorous and most of the time food-constrained shrews consumed less pupae than granivorous-herbivorous voles.
The deer ked (Lipoptena cervi) is an important ectoparasite of moose (Alces alces) that has rapid... more The deer ked (Lipoptena cervi) is an important ectoparasite of moose (Alces alces) that has rapidly invaded Finland during the last 50 years, and is currently found in southern parts of Finnish Lapland. We have studied the invasion, behavior, and ecology of this parasitic fly, and in this paper briefly review the effect of climate on the distribution of deer keds and our recent findings from host-choice experiments. The rapid increase of the deer ked is correlated with high moose densities in Finland. We propose that the availability of suitable hosts, not climate, is the primary factor affecting its northward range expansion. Our host-choice experiments indicated that deer keds are attracted by movement and large, dark objects. Our results suggest that this parasite may continue to spread northwards in the near future, and that its potential impact on cervids and human health warrants attention.
Page 1. Dominance and immune function in the F1 generation of wild caught field crickets Sami Vää... more Page 1. Dominance and immune function in the F1 generation of wild caught field crickets Sami Väänänen, Raine Kortet1) & Markus J. Rantala2) (Department of Biological and Environmental Science, University of Jyväskylä ...
Parasites cause significant economic losses in fish farming, and knowledge of the mechanisms unde... more Parasites cause significant economic losses in fish farming, and knowledge of the mechanisms underlying their effects on hosts is an essential prerequisite of preventative procedures for the parasite problem in hatcheries. One such mechanism is local adaptation of parasites, which should lead to higher infectivity of parasites in sympatric host-parasite combinations compared to corresponding allopatric combinations. In this study, we investigated the infectivity of two ubiquitous species of trematode eye flukes, Diplostomum sp. and Tylodelphus clavata, in their farmed salmonid fish hosts with respect to origin of the parasite and the host. First, we exposed two anadromous and one landlocked Atlantic salmon (Salmo salar) populations to controlled infection by Diplostomum sp. and natural infection by T. clavata. The anadromous salmon populations were local to Diplostomum sp. and non-local to T. clavata. In the case of the landlocked salmon, the population was non-local to Diplostomum sp. and local to T. clavata. Second, we exposed a landlocked population of Arctic charr (Salvelinus alpinus) to Diplostomum sp. cercariae from one non-local and two local parasite populations. The results indicated that eye fluke infectivity in both Atlantic salmon and Arctic charr was 1.5-2.6 times higher in local parasite-host combinations compared to those separated by greater geographical distance. This suggests that diplostomid parasites are able to adapt to local host populations, which may have significant implications such as high abundance and prevalence of the parasites in endangered fish stocks that are maintained in hatcheries.
... However, deer ked reproduction is more limited in other cervids than in moose (Kaunisto et al... more ... However, deer ked reproduction is more limited in other cervids than in moose (Kaunisto et al. 2009). ... Press, pp. 1–18. Kaitala, A. et al. 2009. Deer ked, an ectoparasite of moose in Finland: a brief review of its biology and invasion. Alces 45: 85–88. Kaunisto, S. et al. 2009. ...
ABSTRACT Aphanomyces astaciis among the most serious pathogens affecting European aquatic ecosyst... more ABSTRACT Aphanomyces astaciis among the most serious pathogens affecting European aquatic ecosystems. We demonstrate that both virulence of A. astaciisolates and resistance of native European crayfish stocks vary notably. Some native European crayfish stocks latently carry crayfish plague, indicating adaptation and contemporary co-evolution between host and pathogen. The earliest introduced A. astacigenotypes have adapted to novel, susceptible native European crayfishes, likely under an evolutionary pressure to maintain a necessary host population as an essential habitat. Then, highly virulent genotypes that were introduced together with their original American hosts, have more resistant host populations present in Europe. This creates a dilemma for A. astaci: whether to increase virulence to better utilize invasive American hosts or to reduce virulence to better utilize the native European hosts. All A. astacigenotypes are potent killers, but they already show lowered virulence similarly to previous examples of virulence evolution in novel pathogens.
Sperm production and sperm swimming speed, which most likely affect fertilization under sperm com... more Sperm production and sperm swimming speed, which most likely affect fertilization under sperm competition, are modified by proximate mechanisms. In a comprehensive observational study of free-living and reproductively active Arctic charr (Salvelinus alpinus), we examined the possible modulating effects of male social status (including ornamental development), parasite intensities, and immunity on novel traits indicative of ejaculate quality (e.g., Adenosine triphosphate (ATP) in sperm cells, levels of immunoglobulins attached to sperm cells, and the degree of DNA fragmentation in sperm cells). A multiple regression model showed no relationship between DNA fragmentation in sperm cells and abdominal coloration of charr, suggesting that sperm of colorful males are not better protected against oxidative stress. We found, however, that males with traits indicative of high social status had low amounts of ATP in sperm cells and also sperm cells with low swimming speed. Sperm production, on the other hand, was strongly predicted by parasite intensities only and these associations were mainly positive. Our results suggest that the presence of parasites seems to stimulate sperm production similar to what is observed among males entering subordinate reproductive roles. Thus, if resistance toward parasites is influencing parasite intensities, resistance may also indirectly be important for the "choice" of reproductive role and in turn investment in primary sex traits.
Immunity of parasites has been studied amazingly little, in spite of the fact that parasitic orga... more Immunity of parasites has been studied amazingly little, in spite of the fact that parasitic organisms, especially the arthropod parasites, need immunity to survive their own infections to successfully complete life cycles. Long-term effects of challenging environmental temperatures on immunity have remained unstudied in insects and parasites. Our study species, the deer ked (Lipoptena cervi; Linnaeus 1758), is an invasive, blood-feeding parasitic fly of cervids. Here, it was studied whether thermal stress during the pupal diapause stage could modify adult immunity (encapsulation capacity) in L. cervi. The effect of either a low temperature or high temperature peak, experienced during winter dormancy, on encapsulation response of active adult was tested. It was found that low temperature exposure during diapause, as long as the temperature is not too harsh, had a favourable effect on adult immunity. An abnormal, high temperature peak during pupal winter diapause significantly deteri...
According to the immunocompetence handicap hypothesis, males with attractive sexual ornamentation... more According to the immunocompetence handicap hypothesis, males with attractive sexual ornamentation are more handicapped than their less ornamented rivals because of the immunosuppressive androgens required for the production of secondary sexual characters. Here we studied the predictions of the hypothesis in a wild cyprinid fish, the roach (Rutilus rutilus). We assayed (1) sexual ornamentation (breeding tubercles), (2) circulating androgens (11-ketotestosterone
It has been suggested that human scent works as a signal in mate selection, but the empirical evi... more It has been suggested that human scent works as a signal in mate selection, but the empirical evidence is scarce. Here, we examined whether women's olfactory preferences for a man's scent could be correlated with his testosterone, estradiol, or cortisol concentrations, and whether these preferences change along with the menstrual cycle. In line with previous studies, women in their most fertile period gave the highest attractiveness ratings to all men. However, the intensity ratings by women at different menstrual phases did not significantly differ statistically. Interestingly, we found that cortisol concentration in saliva correlated positively with the attractiveness but not with the intensity ratings of male T-shirt odor by all women's groups. However, neither testosterone nor estradiol was significantly associated with the ratings of attractiveness or intensity. Thus, our study suggests that there could be a novel mechanism for odor-based selection in humans. D
Consistent individual differences in behavioural responses to perceived predation risk may have e... more Consistent individual differences in behavioural responses to perceived predation risk may have extensive ecological and evolutionary implications. We studied the repeatability of boldness across time and its relation to resource holding potential in the noble crayfish, Astacus astacus L., using predator-naïve immature individuals. We followed individual's shelter use both with and without exposure to the chemical and physical cues of predators, and with and without the presence of a conspecific. In addition, we examined if armament, i.e. relative chelae size, would be correlated with individual differences in behaviour. Individuals showed repeatable behaviours across time and context. Individuals that occupied the shelter in competitive dyadic tests also spent more time in the shelter during individual control observations, suggesting that boldness is a personality trait that does not necessarily relate positively to high resource holding potential in the noble crayfish. The relative size of chelae did not correlate with any of the measured behavioural variables. Our results suggest that boldness can be considered as individually consistent and ecologically important personality trait in the noble crayfish.
In contrast to females, tench Tinca tinca (L.) males have large pelvic fins with a thickened and ... more In contrast to females, tench Tinca tinca (L.) males have large pelvic fins with a thickened and bent second fin ray. Males also produce notable ventral protuberances during breeding, but the function of these male ornaments is not known. Using wild-caught fish, we found that both the size of pelvic fins and ventral protuberance were dependent on body mass/length ratio but not necessarily on condition. Plasma testosterone concentration and relative gonad mass were positively correlated with condition factor. Plasma testosterone concentration was not related to measures of non-specific immune function, but correlated positively with the size of pelvic fins corrected for body length. However, the studied male ornaments were not related to the measures of immune defence or to the load of Diplostomum spp. We did not find evidence for male-male dominance or female preference for large male characteristics within the natural variation in these traits. Thus, our study suggests that also other mechanisms than sexual selection on good genes might contribute to the maintenance of sexual dimorphism in tench.
ABSTRACT Seasonality in the immune defence of invertebrates can coincide with environmental varia... more ABSTRACT Seasonality in the immune defence of invertebrates can coincide with environmental variation but whether it is endogenously regulated, via biological clocks, or affected by previous immune challenges remains unclear. Using the native noble crayfish (Astacus astacus) held under constant laboratory conditions for a year, we explored (1) potential endogenous seasonal variation in immune defence, i.e. the encapsulation response, (2) the potential positive effect of repeated challenges with a standardized immune insult in subsequent seasons, i.e. long-lasting immune priming, and (3) whether long-lasting immune priming is dependent on endogenous seasonality. Independent measurements of the encapsulation response in different seasons revealed significant variation and a decrease in autumn. This result indicates previously undetected endogenous seasonal variation in invertebrate immunity. The weaker immune defence observed in autumn, i.e. the reproductive season of crayfish, might be caused by a circannual clock. When corrected for endogenous seasonality, we found no evidence for long-lasting immune priming.
Animals are often individually consistent in their behavior, not only over time, but also across ... more Animals are often individually consistent in their behavior, not only over time, but also across different functional contexts. Recent research has focused on phenotypic and evolutionary mechanisms explaining such personality differences through selection. Parasitism and predation induce important mortality and fitness costs, and are thus main candidates to create and maintain personality differences in the wild. Here, we present data on the behavioral consistency of the Eurasian minnow (Phoxinus phoxinus) from two populations that live in different tributaries of the same river, but whose ecological environment differs fundamentally with regard to predation and parasitism. We experimentally demonstrate that individual minnow in both study populations are consistent in their boldness and activity. However, the two study populations differ notably: in the high predation and parasitism risk population fish show higher mean boldness, but tend to be less active than fish in low predation and parasitism risk population. Parasite (Diplostomum phoxini) load was negatively, but not statistically significantly, associated with fish activity level. Our study suggests that parasitism and predation are likely important agents in the ecology and evolution of animal personalities.
Predation is often considered an important factor for population regulation and in some cases for... more Predation is often considered an important factor for population regulation and in some cases for the invasion success of prey. Small mammalian predation may be a major force in the population regulation of many ground-dwelling invertebrate species. The deer ked (Lipoptena cervi (L., 1758)) is an ectoparasitic fly of cervids. The species has a large distribution area and it has relatively rapidly spread in northern Europe during the previous four decades. The factors possibly regulating the distribution and invasion of this fly are poorly known. During the off-host stage of several months, pupae of deer ked are likely exposed to many ground-dwelling predators. To study whether small mammals would feed on deer keds, we conducted experiments by serving pupae of deer ked to wild-captured common shrews (Sorex araneus L., 1758), bank voles (Myodes glareolus (Schreber, 1780)), field voles (Microtus agrestis (L., 1761)), and semi-wild bank voles, and assessed pupal survival. As a control, we provided alternative food including common nutrients used by small mammals in their natural habitats. The results show that variable amounts of pupae of deer ked are consumed by all small-mammal species studied. Surprisingly, insectivorous and most of the time food-constrained shrews consumed less pupae than granivorous-herbivorous voles.
The deer ked (Lipoptena cervi) is an important ectoparasite of moose (Alces alces) that has rapid... more The deer ked (Lipoptena cervi) is an important ectoparasite of moose (Alces alces) that has rapidly invaded Finland during the last 50 years, and is currently found in southern parts of Finnish Lapland. We have studied the invasion, behavior, and ecology of this parasitic fly, and in this paper briefly review the effect of climate on the distribution of deer keds and our recent findings from host-choice experiments. The rapid increase of the deer ked is correlated with high moose densities in Finland. We propose that the availability of suitable hosts, not climate, is the primary factor affecting its northward range expansion. Our host-choice experiments indicated that deer keds are attracted by movement and large, dark objects. Our results suggest that this parasite may continue to spread northwards in the near future, and that its potential impact on cervids and human health warrants attention.
Page 1. Dominance and immune function in the F1 generation of wild caught field crickets Sami Vää... more Page 1. Dominance and immune function in the F1 generation of wild caught field crickets Sami Väänänen, Raine Kortet1) & Markus J. Rantala2) (Department of Biological and Environmental Science, University of Jyväskylä ...
Parasites cause significant economic losses in fish farming, and knowledge of the mechanisms unde... more Parasites cause significant economic losses in fish farming, and knowledge of the mechanisms underlying their effects on hosts is an essential prerequisite of preventative procedures for the parasite problem in hatcheries. One such mechanism is local adaptation of parasites, which should lead to higher infectivity of parasites in sympatric host-parasite combinations compared to corresponding allopatric combinations. In this study, we investigated the infectivity of two ubiquitous species of trematode eye flukes, Diplostomum sp. and Tylodelphus clavata, in their farmed salmonid fish hosts with respect to origin of the parasite and the host. First, we exposed two anadromous and one landlocked Atlantic salmon (Salmo salar) populations to controlled infection by Diplostomum sp. and natural infection by T. clavata. The anadromous salmon populations were local to Diplostomum sp. and non-local to T. clavata. In the case of the landlocked salmon, the population was non-local to Diplostomum sp. and local to T. clavata. Second, we exposed a landlocked population of Arctic charr (Salvelinus alpinus) to Diplostomum sp. cercariae from one non-local and two local parasite populations. The results indicated that eye fluke infectivity in both Atlantic salmon and Arctic charr was 1.5-2.6 times higher in local parasite-host combinations compared to those separated by greater geographical distance. This suggests that diplostomid parasites are able to adapt to local host populations, which may have significant implications such as high abundance and prevalence of the parasites in endangered fish stocks that are maintained in hatcheries.
... However, deer ked reproduction is more limited in other cervids than in moose (Kaunisto et al... more ... However, deer ked reproduction is more limited in other cervids than in moose (Kaunisto et al. 2009). ... Press, pp. 1–18. Kaitala, A. et al. 2009. Deer ked, an ectoparasite of moose in Finland: a brief review of its biology and invasion. Alces 45: 85–88. Kaunisto, S. et al. 2009. ...
ABSTRACT Aphanomyces astaciis among the most serious pathogens affecting European aquatic ecosyst... more ABSTRACT Aphanomyces astaciis among the most serious pathogens affecting European aquatic ecosystems. We demonstrate that both virulence of A. astaciisolates and resistance of native European crayfish stocks vary notably. Some native European crayfish stocks latently carry crayfish plague, indicating adaptation and contemporary co-evolution between host and pathogen. The earliest introduced A. astacigenotypes have adapted to novel, susceptible native European crayfishes, likely under an evolutionary pressure to maintain a necessary host population as an essential habitat. Then, highly virulent genotypes that were introduced together with their original American hosts, have more resistant host populations present in Europe. This creates a dilemma for A. astaci: whether to increase virulence to better utilize invasive American hosts or to reduce virulence to better utilize the native European hosts. All A. astacigenotypes are potent killers, but they already show lowered virulence similarly to previous examples of virulence evolution in novel pathogens.
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Papers by Raine Kortet