Michael Siva-jothy - Academia.edu (original) (raw)
Papers by Michael Siva-jothy
A panel of monoclonal antibodies (mAbs) raised against whole haemocytes from Periplaneta american... more A panel of monoclonal antibodies (mAbs) raised against whole haemocytes from Periplaneta americana has revealed two broad categories of immunogens. Three mAbs showed reactivity with membrane-bound antigens on the three major morphological classes of haemocyte as well as the basement membrane of tissues in contact with the haemocoel. Moreover, this reactiv - ity showed heterogeneity within morphotypes: this het- erogeneity
During the course of ontogeny, odonates switch from being aquatic larvae to being terrestrial adu... more During the course of ontogeny, odonates switch from being aquatic larvae to being terrestrial adults. Ontogenetic niche shift theory proposes that such shifts are adaptive and have evolved to maximize a growth rate (size) to mortality rate ratio. Individuals should therefore switch from one niche to the other at an optimal size or state. Since the majority of odonates are seasonal breeders, the extent to which the switch is optimal will depend upon the time and the resources available during postembryonic development. We collected a cohort of larvae that varied in how close they were to eclosion and reared them on either a high-nutrition or a low-nutrition diet. We then determined the relative influence of both time and nutritional constraints on survival and development rate, as well as the body size, size-corrected flight muscle mass and fat reserves of individuals at eclosion. Damselflies in both high-and low-nutrition treatments responded to a short development period by developing faster and reducing their body size, but did not change their proportional investment in fat reserves and flight muscle. Reduced larval nutrition resulted in decreased body size, flight muscle mass and fat reserves at eclosion. However, it had no effect on survival to eclosion, or development rate. We discuss these results in terms of the influence that time and nutritional constraints have on odonate development patterns and fitness.
BMC evolutionary biology, 2006
Colour polymorphisms are widespread and one of the prime examples is the colour polymorphism in f... more Colour polymorphisms are widespread and one of the prime examples is the colour polymorphism in female coenagrionid damselflies: one female morph resembles the male colour (andromorph) while one, or more, female morphs are described as typically female (gynomorph). However, the selective pressures leading to the evolution and maintenance of this polymorphism are not clear. Here, based on the hypothesis that coloration and especially black patterning can be related to resistance against pathogens, we investigated the differences in immune function and parasite resistance between the different female morphs and males. Our studies of immune function revealed no differences in immune function between the female morphs but between the sexes in adult damselflies. In an experimental infection females infected shortly after emergence showed a higher resistance against a fungal pathogen than males, however female morphs did not differ in resistance. In a field sample of adult damselflies we ...
The bed bug, Cimex lectularius, has a unique mode of copulation termed ''traumatic'' insemination... more The bed bug, Cimex lectularius, has a unique mode of copulation termed ''traumatic'' insemination in Monograph of the Cimicidae, ed. Usinger, R. (Entomol. Soc. Am., Philadelphia), pp. 81-167] during which the male pierces the female's abdominal wall with his external genitalia and inseminates into her body cavity [Carayon, J. (1966) in Monograph of the Cimicidae, ed. Usinger, R. (Entomol. Soc. Am., Philadelphia), pp. 81-167].
Physiological Entomology, 1989
ABSTRACT. A novel combination of adaptations resulting from sperm competition is demonstrated for... more ABSTRACT. A novel combination of adaptations resulting from sperm competition is demonstrated for the tree cricket Truljalia hibinonis (Matsumura)(Podoscirtinae: Gryllidae: Orthoptera). 87.5% of the semen of previous males is displaced onto the penis of the ...
Physiological Entomology, 1998
Males and females of the Japanese calopterygid damselfly, Matrona basilaris japonica Fester, show... more Males and females of the Japanese calopterygid damselfly, Matrona basilaris japonica Fester, showed a rapid (within 24 h), and significant reduction in immune system function (encapsulation response) after reproductive activity (copulation or oviposition). A similar, but non-significant, change occurred in males that conducted energetically costly behaviour (fighting). These data suggest that there may be physiological costs other than energy-based trade-offs
Proceedings of The Royal Society B: Biological Sciences, 2003
Males of the bedbug, Cimex lectularius, traumatically inseminate females by inserting a needle-li... more Males of the bedbug, Cimex lectularius, traumatically inseminate females by inserting a needle-like intromittent organ (penis) through the female's abdominal wall after she has fed. We demonstrate that: (i) mating duration determines ejaculate size; (ii) a female's first copulation in a bout of copulations always lasts longer than subsequent copulations; (iii) the intromittent organ bears sensillae; (iv) males use their intromittent organ to 'taste' whether their current mate has recently copulated; and (v) the consequence of detecting female mating status is the reduction of copulation duration and ejaculate size. We discuss why male bedbugs might show this pattern of ejaculate-size adjustment.
Proceedings of The Royal Society B: Biological Sciences, 1995
... (Charpentier) MICHAEL T. SIVA-JOTHY AND ROWAN E. HOOPER Department of Animal and Plant Scienc... more ... (Charpentier) MICHAEL T. SIVA-JOTHY AND ROWAN E. HOOPER Department of Animal and Plant Sciences, University of Sheffield, Sheffield SJO 2UQ, UK SUMMARY ... Printed in Great Britain Page 2. 314 MT Siva-Jothy and RE Hooper Stored sperm in damselfy females ...
Proceedings of The Royal Society B: Biological Sciences, 1996
Males of the damselfly Calopteryx splendens xanthostoma (Charpentier) demonstrate territorial and... more Males of the damselfly Calopteryx splendens xanthostoma (Charpentier) demonstrate territorial and non-territorial mate securing tactics. Non-territorial males obtain a territory in one of two ways: they either wait for a territory to become vacant, or they fight with and displace a territory holder. The estimated reproductive success of territorial males was a thousand times greater than that of non-territorial males,
Summary. Males of the damselfly Mnais pruinosa pruinosa were observed to use three different tact... more Summary. Males of the damselfly Mnais pruinosa pruinosa were observed to use three different tactics to secure mates. The mean duration of copulation differed between the three observed tatics and re- sulted in varying degrees of sperm removal and insemination. It is shown that the last male to mate had almost 100% sperm precedence immediately after copulation regardless of the
Advances in Insect Physiology, 2005
We review recent advances in our understanding of the mechanisms of insect immune defence, but do... more We review recent advances in our understanding of the mechanisms of insect immune defence, but do so in a framework defined by the ecological and ADVANCES IN INSECT PHYSIOLOGY VOL. 32
Insects As Natural Enemies, 2007
Trends in Ecology & Evolution, 1995
Science, 2003
Ecological immunology is a rapidly expanding field that examines the causes and consequences of v... more Ecological immunology is a rapidly expanding field that examines the causes and consequences of variation in immune function in the context of evolution and of ecology. Millions of invertebrate species rely solely on innate immunity, compared with only 45,000 vertebrate species that rely additionally on an acquired immune system. Despite this difference in diversity, most studies of ecological immunology focus on vertebrates. Here we review recent progress derived largely from the mechanistic analysis of invertebrate innate immunity. Using this empirical base, we pose general questions in areas that are of central importance for the development of ecological immunology.
Proceedings of the Royal Society B: Biological Sciences, 2003
The frequent wounding of female bedbugs (Cimex lectularius: Cimicidae) during copulation has been... more The frequent wounding of female bedbugs (Cimex lectularius: Cimicidae) during copulation has been shown to decrease their fitness, but how females have responded to this cost in evolutionary terms is unclear. The evolution of a unique anatomical structure found in female bedbugs, the spermalege, into which the male's intromittent organ passes during traumatic insemination, is a possible counteradaptation to harmful male traits. Several functions have been proposed for this organ, and we test two hypotheses related to its role in sexual conflict. We examine the hypotheses that the spermalege functions to (i) defend against pathogens introduced during traumatic insemination; and (ii) reduce the costs of wound healing during traumatic insemination. Our results support the 'defence against pathogens' hypothesis, suggesting that the evolution of this unique cimicid organ resulted, at least partly, from selection to reduce the costs of mating-associated infection. We found no evidence that the spermalege reduces the costs of wound healing.
Proceedings of the Royal Society B: Biological Sciences, 2003
Males of the bedbug, Cimex lectularius, traumatically inseminate females by inserting a needle-li... more Males of the bedbug, Cimex lectularius, traumatically inseminate females by inserting a needle-like intromittent organ (penis) through the female's abdominal wall after she has fed. We demonstrate that: (i) mating duration determines ejaculate size; (ii) a female's first copulation in a bout of copulations always lasts longer than subsequent copulations; (iii) the intromittent organ bears sensillae; (iv) males use their intromittent organ to 'taste' whether their current mate has recently copulated; and (v) the consequence of detecting female mating status is the reduction of copulation duration and ejaculate size. We discuss why male bedbugs might show this pattern of ejaculate-size adjustment.
Proceedings of the Royal Society B: Biological Sciences, 2003
A primary infection by a parasite may indicate a higher risk of being reinfected in the near futu... more A primary infection by a parasite may indicate a higher risk of being reinfected in the near future (since infection may indicate that enemies are becoming more abundant). Acquired immunity does not exist in invertebrates despite the fact that they also face increased risks of reinfection following primary exposure. However, when subjected to immune insult, insects can produce immune responses that persist for long enough to provide prophylaxis. Because these immune responses are costly, persistence must be maintained through a selective advantage. We tested for the possibility that these long-lasting immune responses provided increased resistance to later infections by experimentally mimicking a primary immune insult (pre-challenge) in larvae of the mealworm beetle, Tenebrio molitor, with lipopolysaccharides (LPS) prior to early or late exposure to spores of the entomopathogenic fungus Metarhizium anisopliae. We found that pre-challenged larvae produced a long-lasting antimicrobial response, which provided a survival benefit when the larvae were exposed to fungal infection. These results suggest that the observed response is functionally 'adaptive'.
Proceedings of the Royal Society B: Biological Sciences, 2004
The strength of selection on immune function in wild populations has only been examined in a few ... more The strength of selection on immune function in wild populations has only been examined in a few vertebrate species. We report the results from a study measuring selection on a key insect immune enzyme, phenoloxidase (PO), in a wild population of the damselfly Calopteryx xanthostoma. We followed individually marked males from the pre-reproductive adult phase and recorded their lifetime mating success. We found positive selection on PO activity in response to an immune insult, but no selection on wing-spot quality, a trait actively displayed to females during courtship. We suggest that positive selection on PO activity in the year of study may be explained by annual fluctuations in parasite loads.
Proceedings of the Royal Society B: Biological Sciences, 1995
... (Charpentier) MICHAEL T. SIVA-JOTHY AND ROWAN E. HOOPER Department of Animal and Plant Scienc... more ... (Charpentier) MICHAEL T. SIVA-JOTHY AND ROWAN E. HOOPER Department of Animal and Plant Sciences, University of Sheffield, Sheffield SJO 2UQ, UK SUMMARY ... Printed in Great Britain Page 2. 314 MT Siva-Jothy and RE Hooper Stored sperm in damselfy females ...
A panel of monoclonal antibodies (mAbs) raised against whole haemocytes from Periplaneta american... more A panel of monoclonal antibodies (mAbs) raised against whole haemocytes from Periplaneta americana has revealed two broad categories of immunogens. Three mAbs showed reactivity with membrane-bound antigens on the three major morphological classes of haemocyte as well as the basement membrane of tissues in contact with the haemocoel. Moreover, this reactiv - ity showed heterogeneity within morphotypes: this het- erogeneity
During the course of ontogeny, odonates switch from being aquatic larvae to being terrestrial adu... more During the course of ontogeny, odonates switch from being aquatic larvae to being terrestrial adults. Ontogenetic niche shift theory proposes that such shifts are adaptive and have evolved to maximize a growth rate (size) to mortality rate ratio. Individuals should therefore switch from one niche to the other at an optimal size or state. Since the majority of odonates are seasonal breeders, the extent to which the switch is optimal will depend upon the time and the resources available during postembryonic development. We collected a cohort of larvae that varied in how close they were to eclosion and reared them on either a high-nutrition or a low-nutrition diet. We then determined the relative influence of both time and nutritional constraints on survival and development rate, as well as the body size, size-corrected flight muscle mass and fat reserves of individuals at eclosion. Damselflies in both high-and low-nutrition treatments responded to a short development period by developing faster and reducing their body size, but did not change their proportional investment in fat reserves and flight muscle. Reduced larval nutrition resulted in decreased body size, flight muscle mass and fat reserves at eclosion. However, it had no effect on survival to eclosion, or development rate. We discuss these results in terms of the influence that time and nutritional constraints have on odonate development patterns and fitness.
BMC evolutionary biology, 2006
Colour polymorphisms are widespread and one of the prime examples is the colour polymorphism in f... more Colour polymorphisms are widespread and one of the prime examples is the colour polymorphism in female coenagrionid damselflies: one female morph resembles the male colour (andromorph) while one, or more, female morphs are described as typically female (gynomorph). However, the selective pressures leading to the evolution and maintenance of this polymorphism are not clear. Here, based on the hypothesis that coloration and especially black patterning can be related to resistance against pathogens, we investigated the differences in immune function and parasite resistance between the different female morphs and males. Our studies of immune function revealed no differences in immune function between the female morphs but between the sexes in adult damselflies. In an experimental infection females infected shortly after emergence showed a higher resistance against a fungal pathogen than males, however female morphs did not differ in resistance. In a field sample of adult damselflies we ...
The bed bug, Cimex lectularius, has a unique mode of copulation termed ''traumatic'' insemination... more The bed bug, Cimex lectularius, has a unique mode of copulation termed ''traumatic'' insemination in Monograph of the Cimicidae, ed. Usinger, R. (Entomol. Soc. Am., Philadelphia), pp. 81-167] during which the male pierces the female's abdominal wall with his external genitalia and inseminates into her body cavity [Carayon, J. (1966) in Monograph of the Cimicidae, ed. Usinger, R. (Entomol. Soc. Am., Philadelphia), pp. 81-167].
Physiological Entomology, 1989
ABSTRACT. A novel combination of adaptations resulting from sperm competition is demonstrated for... more ABSTRACT. A novel combination of adaptations resulting from sperm competition is demonstrated for the tree cricket Truljalia hibinonis (Matsumura)(Podoscirtinae: Gryllidae: Orthoptera). 87.5% of the semen of previous males is displaced onto the penis of the ...
Physiological Entomology, 1998
Males and females of the Japanese calopterygid damselfly, Matrona basilaris japonica Fester, show... more Males and females of the Japanese calopterygid damselfly, Matrona basilaris japonica Fester, showed a rapid (within 24 h), and significant reduction in immune system function (encapsulation response) after reproductive activity (copulation or oviposition). A similar, but non-significant, change occurred in males that conducted energetically costly behaviour (fighting). These data suggest that there may be physiological costs other than energy-based trade-offs
Proceedings of The Royal Society B: Biological Sciences, 2003
Males of the bedbug, Cimex lectularius, traumatically inseminate females by inserting a needle-li... more Males of the bedbug, Cimex lectularius, traumatically inseminate females by inserting a needle-like intromittent organ (penis) through the female's abdominal wall after she has fed. We demonstrate that: (i) mating duration determines ejaculate size; (ii) a female's first copulation in a bout of copulations always lasts longer than subsequent copulations; (iii) the intromittent organ bears sensillae; (iv) males use their intromittent organ to 'taste' whether their current mate has recently copulated; and (v) the consequence of detecting female mating status is the reduction of copulation duration and ejaculate size. We discuss why male bedbugs might show this pattern of ejaculate-size adjustment.
Proceedings of The Royal Society B: Biological Sciences, 1995
... (Charpentier) MICHAEL T. SIVA-JOTHY AND ROWAN E. HOOPER Department of Animal and Plant Scienc... more ... (Charpentier) MICHAEL T. SIVA-JOTHY AND ROWAN E. HOOPER Department of Animal and Plant Sciences, University of Sheffield, Sheffield SJO 2UQ, UK SUMMARY ... Printed in Great Britain Page 2. 314 MT Siva-Jothy and RE Hooper Stored sperm in damselfy females ...
Proceedings of The Royal Society B: Biological Sciences, 1996
Males of the damselfly Calopteryx splendens xanthostoma (Charpentier) demonstrate territorial and... more Males of the damselfly Calopteryx splendens xanthostoma (Charpentier) demonstrate territorial and non-territorial mate securing tactics. Non-territorial males obtain a territory in one of two ways: they either wait for a territory to become vacant, or they fight with and displace a territory holder. The estimated reproductive success of territorial males was a thousand times greater than that of non-territorial males,
Summary. Males of the damselfly Mnais pruinosa pruinosa were observed to use three different tact... more Summary. Males of the damselfly Mnais pruinosa pruinosa were observed to use three different tactics to secure mates. The mean duration of copulation differed between the three observed tatics and re- sulted in varying degrees of sperm removal and insemination. It is shown that the last male to mate had almost 100% sperm precedence immediately after copulation regardless of the
Advances in Insect Physiology, 2005
We review recent advances in our understanding of the mechanisms of insect immune defence, but do... more We review recent advances in our understanding of the mechanisms of insect immune defence, but do so in a framework defined by the ecological and ADVANCES IN INSECT PHYSIOLOGY VOL. 32
Insects As Natural Enemies, 2007
Trends in Ecology & Evolution, 1995
Science, 2003
Ecological immunology is a rapidly expanding field that examines the causes and consequences of v... more Ecological immunology is a rapidly expanding field that examines the causes and consequences of variation in immune function in the context of evolution and of ecology. Millions of invertebrate species rely solely on innate immunity, compared with only 45,000 vertebrate species that rely additionally on an acquired immune system. Despite this difference in diversity, most studies of ecological immunology focus on vertebrates. Here we review recent progress derived largely from the mechanistic analysis of invertebrate innate immunity. Using this empirical base, we pose general questions in areas that are of central importance for the development of ecological immunology.
Proceedings of the Royal Society B: Biological Sciences, 2003
The frequent wounding of female bedbugs (Cimex lectularius: Cimicidae) during copulation has been... more The frequent wounding of female bedbugs (Cimex lectularius: Cimicidae) during copulation has been shown to decrease their fitness, but how females have responded to this cost in evolutionary terms is unclear. The evolution of a unique anatomical structure found in female bedbugs, the spermalege, into which the male's intromittent organ passes during traumatic insemination, is a possible counteradaptation to harmful male traits. Several functions have been proposed for this organ, and we test two hypotheses related to its role in sexual conflict. We examine the hypotheses that the spermalege functions to (i) defend against pathogens introduced during traumatic insemination; and (ii) reduce the costs of wound healing during traumatic insemination. Our results support the 'defence against pathogens' hypothesis, suggesting that the evolution of this unique cimicid organ resulted, at least partly, from selection to reduce the costs of mating-associated infection. We found no evidence that the spermalege reduces the costs of wound healing.
Proceedings of the Royal Society B: Biological Sciences, 2003
Males of the bedbug, Cimex lectularius, traumatically inseminate females by inserting a needle-li... more Males of the bedbug, Cimex lectularius, traumatically inseminate females by inserting a needle-like intromittent organ (penis) through the female's abdominal wall after she has fed. We demonstrate that: (i) mating duration determines ejaculate size; (ii) a female's first copulation in a bout of copulations always lasts longer than subsequent copulations; (iii) the intromittent organ bears sensillae; (iv) males use their intromittent organ to 'taste' whether their current mate has recently copulated; and (v) the consequence of detecting female mating status is the reduction of copulation duration and ejaculate size. We discuss why male bedbugs might show this pattern of ejaculate-size adjustment.
Proceedings of the Royal Society B: Biological Sciences, 2003
A primary infection by a parasite may indicate a higher risk of being reinfected in the near futu... more A primary infection by a parasite may indicate a higher risk of being reinfected in the near future (since infection may indicate that enemies are becoming more abundant). Acquired immunity does not exist in invertebrates despite the fact that they also face increased risks of reinfection following primary exposure. However, when subjected to immune insult, insects can produce immune responses that persist for long enough to provide prophylaxis. Because these immune responses are costly, persistence must be maintained through a selective advantage. We tested for the possibility that these long-lasting immune responses provided increased resistance to later infections by experimentally mimicking a primary immune insult (pre-challenge) in larvae of the mealworm beetle, Tenebrio molitor, with lipopolysaccharides (LPS) prior to early or late exposure to spores of the entomopathogenic fungus Metarhizium anisopliae. We found that pre-challenged larvae produced a long-lasting antimicrobial response, which provided a survival benefit when the larvae were exposed to fungal infection. These results suggest that the observed response is functionally 'adaptive'.
Proceedings of the Royal Society B: Biological Sciences, 2004
The strength of selection on immune function in wild populations has only been examined in a few ... more The strength of selection on immune function in wild populations has only been examined in a few vertebrate species. We report the results from a study measuring selection on a key insect immune enzyme, phenoloxidase (PO), in a wild population of the damselfly Calopteryx xanthostoma. We followed individually marked males from the pre-reproductive adult phase and recorded their lifetime mating success. We found positive selection on PO activity in response to an immune insult, but no selection on wing-spot quality, a trait actively displayed to females during courtship. We suggest that positive selection on PO activity in the year of study may be explained by annual fluctuations in parasite loads.
Proceedings of the Royal Society B: Biological Sciences, 1995
... (Charpentier) MICHAEL T. SIVA-JOTHY AND ROWAN E. HOOPER Department of Animal and Plant Scienc... more ... (Charpentier) MICHAEL T. SIVA-JOTHY AND ROWAN E. HOOPER Department of Animal and Plant Sciences, University of Sheffield, Sheffield SJO 2UQ, UK SUMMARY ... Printed in Great Britain Page 2. 314 MT Siva-Jothy and RE Hooper Stored sperm in damselfy females ...