The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Irina S Khokhlova - One of the best experts on this subject based on the ideXlab platform.
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Reproductive performance in generalist haematophagous ectoparasites: maternal environment, rearing conditions or both?
Parasitology Research, 2019Co-Authors: Luther Van Der Mescht, Irina S Khokhlova, Elena N. Surkova, Elizabeth M. Warburton, Boris R KrasnovAbstract:We tested whether and how the maternal environment (i.e. host species exploited by a mother), rearing conditions (i.e. host species exploited by her offspring) or both (i.e. matches and mismatches in host species exploited by a mother and her offspring) affect reproductive performance in the offspring. We experimentally manipulated maternal and rearing environments in two generalist fleas ( Xenopsylla conformis and Xenopsylla ramesis ) implementing a factorial cross-rearing design. Mothers exploited either the principal host (PH) or auxiliary hosts that were either closely (CAH) or distantly related (DAH) to the PH. After six generations of infesting a given host species, we cross-reared fleas within and between host species. These fleas reproduced and we measured their reproductive performance both quantitatively (i.e. egg number) and qualitatively (i.e. egg size, development time, body size of the next generation). We found that identity of the host a flea was reared on (=actual host) had the strongest effect on its performance. Individuals reared on the PH performed considerably better than those reared on either auxiliary host. Moreover, fleas reared on a CAH performed better than those reared on a DAH. Actual host identity also had a stronger effect on reproductive performance in X. ramesis than in X. conformis . Nevertheless, there was no difference in performance between match and mismatch maternal and actual host identities. We conclude that rearing environment has the strongest effect on fitness in generalist parasites. Moreover, phylogenetic distance between an auxiliary host and the PH determines the level of suitability of the former.
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evidence for a negative fitness density relationship between parent density and offspring quality for two Xenopsylla spp parasitic on desert mammals
Medical and Veterinary Entomology, 2008Co-Authors: Boris R Krasnov, Irina S Khokhlova, A Hovhanyan, Allan A DegenAbstract:: We tested the hypothesis of negative fitness-density relationships and predicted that an increase in the density of parent fleas would result in lower survival rates and longer development time of pre-imagoes as well as shorter time to death from starvation of newly emerged imagoes. These predictions were experimentally tested on Xenopsylla conformis Wagner and Xenopsylla ramesis Rothschild feeding on two rodent species, Meriones crassus Sundevall or Dipodillus dasyurus Wagner. Survival of larvae and pupae, but not eggs, was negatively affected by parent density. An increase in parent density led to a decrease in the number of imagoes of the next generation. Eggs of both species developed faster when the parents were at low densities on either host. The same was true for larval X. ramesis, but not larval X. conformis. The negative effects of parent density on the duration of pupal development were evident in X. conformis, parents of which fed on both hosts, and X. ramesis from parents fed on M. crassus, whereas X. ramesis from parents fed on D. dasyurus developed faster at low densities. A negative effect of density on the development of offspring from egg to imago in X. conformis was manifested mainly when parent fleas fed on D. dasyurus, whereas the negative effect of density on offspring development in X. ramesis was manifested mainly when parent fleas fed on M. crassus. Although there was no general effect of parent density on the resistance of imago offspring to starvation, male X. ramesis from parents fed at the highest density survived starvation for significantly shorter times compared with those from parents fed at lower densities. Manifestation of the negative effect of parent density on offspring quality appears to vary with flea species and may be affected by host species.
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water balance in two species of desert fleas Xenopsylla ramesis and x conformis siphonaptera pulicidae
Journal of Medical Entomology, 2002Co-Authors: Laura J Fielden, Boris R Krasnov, Kelly M Still, Irina S KhokhlovaAbstract:The role of water balance capabilities of seas was examined in desert habitats. The seas studied were Xenopsylla ramesis Rothschild and Xenopsylla conformis Wagner. Both seas occur on SundevallOs jird, Meriones crassus, in the Negev Highlands of Israel but in different macro- and microhabitats. Because M. crassus occurs in several habitats of the highlands, it was used as a model for investigating the effect of habitat parameters on species composition of seas within a host species. Water balance parameters investigated were the range of humidities over which active water uptake occurs in the larvae and prepupae of X. ramesis and X. conformis. Critical equilibrium humidity estimates were close to 65% RH for larvae and prepupae of both species. Water loss rates were determined for each life stage, except eggs, and represented water loss from cuticular, respiratory, and other body openings) under conditions of little or no bulk air movement. When converted to a proportional rate (1.44 Ð2.37% mass loss h 1 ) water loss rates did not differ signiÞcantly between stages or species. Thus, geographic separation of X. ramesis and X. conformis could not be explained by any difference in water uptake capabilities or water loss rates. Other factors that may be important include interspeciÞc competition for resource availability among larval seas and effect of soil texture on cocoon construction.
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development rates of two Xenopsylla flea species in relation to air temperature and humidity
Medical and Veterinary Entomology, 2001Co-Authors: Boris R Krasnov, Irina S Khokhlova, Laura J Fielden, Nadezhda V BurdelovaAbstract:Abstract. The rate of development of immature fleas, Xenopsylla conformisWagner and Xenopsylla ramesis Rothschild (Siphonaptera: Xenopsyllidae) wasstudied in the laboratory at 25°C and 28°C with 40, 55, 75 and 92% relativehumidity (RH). These fleas are separately associated with the host jird Merionescrassus Sundevall in different microhabitats of the Ramon erosion cirque, NegevHighlands, Israel. This study of basic climatic factors in relation to flea bionomicsprovides the basis for ecological investigations to interpret reasons for paratopiclocal distributions of these two species of congeneric fleas on the same host. Bothair temperature and RH were positively correlated with duration of egg and larvalstages in both species. Change of humidity between egg and larval environmentsdid not affect duration of larval development at any temperature. At eachtemperature and RH, the eggs and larvae of X. ramesis did not differ betweenmales and females in the duration of their development, whereas female eggs andlarvae of X. conformis usually developed significantly faster than those of males.For both species, male pupae developed slower than female pupae at the same airtemperature and RH. Air temperature, but not RH, affected the duration of pupaldevelopment. At each humidity, duration of the pupal stage was significantly longerat 25°C than at 28°C: 15.3 6 1.7 vs. 11.7 6 1.2 days in X. conformis; 14.1 6 2.0vs. 11.5 6 1.7 days in X. ramesis, with a significantly shorter pupal period of thelatter species at 25°C. These limited interspecific bionomic contrasts in relation tobasic climatic factors appear insufficient to explain the differential habitatdistributions of X. conformis and X. ramesisKey words. Meriones crassus, Xenopsylla conformis, X. ramesis, developmentrate, eggs, females, jird, larvae, males, pupae, relative humidity, temperature,Negev, Israel.
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respiratory gas exchange in the flea Xenopsylla conformis siphonaptera pulicidae
Journal of Medical Entomology, 2001Co-Authors: Laura J Fielden, Boris R Krasnov, Irina S KhokhlovaAbstract:Respiratory gas exchange was measured in various developmental stages of the flea Xenopsylla conformis mycerini (Rothschild, 1904) originating from the central Negev in Israel. Gas exchange in fleas was measured using a flow-through respirometry system that monitored CO2 emission. Lowest metabolic rates were found in the cocooned stage, which included prepupae, early stage pupae, late stage pupae, and preemerged adults. Newly emerged adults and feeding larvae had metabolic rates 2.5–3.0 times greater than those for the cocooned stages. Highest rates of gas exchange were found in feeding fleas. The low metabolic rates of the cocooned stages is thought to contribute to their ability to survive for longer periods than free-living larvae and adults.
Boris R Krasnov - One of the best experts on this subject based on the ideXlab platform.
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Reproductive performance in generalist haematophagous ectoparasites: maternal environment, rearing conditions or both?
Parasitology Research, 2019Co-Authors: Luther Van Der Mescht, Irina S Khokhlova, Elena N. Surkova, Elizabeth M. Warburton, Boris R KrasnovAbstract:We tested whether and how the maternal environment (i.e. host species exploited by a mother), rearing conditions (i.e. host species exploited by her offspring) or both (i.e. matches and mismatches in host species exploited by a mother and her offspring) affect reproductive performance in the offspring. We experimentally manipulated maternal and rearing environments in two generalist fleas ( Xenopsylla conformis and Xenopsylla ramesis ) implementing a factorial cross-rearing design. Mothers exploited either the principal host (PH) or auxiliary hosts that were either closely (CAH) or distantly related (DAH) to the PH. After six generations of infesting a given host species, we cross-reared fleas within and between host species. These fleas reproduced and we measured their reproductive performance both quantitatively (i.e. egg number) and qualitatively (i.e. egg size, development time, body size of the next generation). We found that identity of the host a flea was reared on (=actual host) had the strongest effect on its performance. Individuals reared on the PH performed considerably better than those reared on either auxiliary host. Moreover, fleas reared on a CAH performed better than those reared on a DAH. Actual host identity also had a stronger effect on reproductive performance in X. ramesis than in X. conformis . Nevertheless, there was no difference in performance between match and mismatch maternal and actual host identities. We conclude that rearing environment has the strongest effect on fitness in generalist parasites. Moreover, phylogenetic distance between an auxiliary host and the PH determines the level of suitability of the former.
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evidence for a negative fitness density relationship between parent density and offspring quality for two Xenopsylla spp parasitic on desert mammals
Medical and Veterinary Entomology, 2008Co-Authors: Boris R Krasnov, Irina S Khokhlova, A Hovhanyan, Allan A DegenAbstract:: We tested the hypothesis of negative fitness-density relationships and predicted that an increase in the density of parent fleas would result in lower survival rates and longer development time of pre-imagoes as well as shorter time to death from starvation of newly emerged imagoes. These predictions were experimentally tested on Xenopsylla conformis Wagner and Xenopsylla ramesis Rothschild feeding on two rodent species, Meriones crassus Sundevall or Dipodillus dasyurus Wagner. Survival of larvae and pupae, but not eggs, was negatively affected by parent density. An increase in parent density led to a decrease in the number of imagoes of the next generation. Eggs of both species developed faster when the parents were at low densities on either host. The same was true for larval X. ramesis, but not larval X. conformis. The negative effects of parent density on the duration of pupal development were evident in X. conformis, parents of which fed on both hosts, and X. ramesis from parents fed on M. crassus, whereas X. ramesis from parents fed on D. dasyurus developed faster at low densities. A negative effect of density on the development of offspring from egg to imago in X. conformis was manifested mainly when parent fleas fed on D. dasyurus, whereas the negative effect of density on offspring development in X. ramesis was manifested mainly when parent fleas fed on M. crassus. Although there was no general effect of parent density on the resistance of imago offspring to starvation, male X. ramesis from parents fed at the highest density survived starvation for significantly shorter times compared with those from parents fed at lower densities. Manifestation of the negative effect of parent density on offspring quality appears to vary with flea species and may be affected by host species.
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host defence versus intraspecific competition in the regulation of infrapopulations of the flea Xenopsylla conformis on its rodent host meriones crassus
International Journal for Parasitology, 2007Co-Authors: Hadas Hawlena, Boris R Krasnov, Zvika Abramsky, David SaltzAbstract:Mechanisms that regulate parasite populations may influence the evolution of hosts and parasites, as well as the stability of host-parasite dynamics but are still poorly understood. A manipulation experiment on the grooming ability of rodent hosts (Meriones crassus) and flea (Xenopsylla conformis) densities on these hosts successfully disentangled two possible regulating mechanisms: (i) behavioural defence of the host and (ii) intraspecific competition among parasites, and revealed their importance in suppressing the feeding of fleas. Moreover, the results suggest that flea competition is direct and is not mediated by host grooming, immune response, or parasite-induced damage to the host. These mechanisms, together with interspecific competition and density-dependent parasite-induced host damage, may limit the parasite burden on an individual host and may prevent parasites from overexploiting their host population.
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water balance in two species of desert fleas Xenopsylla ramesis and x conformis siphonaptera pulicidae
Journal of Medical Entomology, 2002Co-Authors: Laura J Fielden, Boris R Krasnov, Kelly M Still, Irina S KhokhlovaAbstract:The role of water balance capabilities of seas was examined in desert habitats. The seas studied were Xenopsylla ramesis Rothschild and Xenopsylla conformis Wagner. Both seas occur on SundevallOs jird, Meriones crassus, in the Negev Highlands of Israel but in different macro- and microhabitats. Because M. crassus occurs in several habitats of the highlands, it was used as a model for investigating the effect of habitat parameters on species composition of seas within a host species. Water balance parameters investigated were the range of humidities over which active water uptake occurs in the larvae and prepupae of X. ramesis and X. conformis. Critical equilibrium humidity estimates were close to 65% RH for larvae and prepupae of both species. Water loss rates were determined for each life stage, except eggs, and represented water loss from cuticular, respiratory, and other body openings) under conditions of little or no bulk air movement. When converted to a proportional rate (1.44 Ð2.37% mass loss h 1 ) water loss rates did not differ signiÞcantly between stages or species. Thus, geographic separation of X. ramesis and X. conformis could not be explained by any difference in water uptake capabilities or water loss rates. Other factors that may be important include interspeciÞc competition for resource availability among larval seas and effect of soil texture on cocoon construction.
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development rates of two Xenopsylla flea species in relation to air temperature and humidity
Medical and Veterinary Entomology, 2001Co-Authors: Boris R Krasnov, Irina S Khokhlova, Laura J Fielden, Nadezhda V BurdelovaAbstract:Abstract. The rate of development of immature fleas, Xenopsylla conformisWagner and Xenopsylla ramesis Rothschild (Siphonaptera: Xenopsyllidae) wasstudied in the laboratory at 25°C and 28°C with 40, 55, 75 and 92% relativehumidity (RH). These fleas are separately associated with the host jird Merionescrassus Sundevall in different microhabitats of the Ramon erosion cirque, NegevHighlands, Israel. This study of basic climatic factors in relation to flea bionomicsprovides the basis for ecological investigations to interpret reasons for paratopiclocal distributions of these two species of congeneric fleas on the same host. Bothair temperature and RH were positively correlated with duration of egg and larvalstages in both species. Change of humidity between egg and larval environmentsdid not affect duration of larval development at any temperature. At eachtemperature and RH, the eggs and larvae of X. ramesis did not differ betweenmales and females in the duration of their development, whereas female eggs andlarvae of X. conformis usually developed significantly faster than those of males.For both species, male pupae developed slower than female pupae at the same airtemperature and RH. Air temperature, but not RH, affected the duration of pupaldevelopment. At each humidity, duration of the pupal stage was significantly longerat 25°C than at 28°C: 15.3 6 1.7 vs. 11.7 6 1.2 days in X. conformis; 14.1 6 2.0vs. 11.5 6 1.7 days in X. ramesis, with a significantly shorter pupal period of thelatter species at 25°C. These limited interspecific bionomic contrasts in relation tobasic climatic factors appear insufficient to explain the differential habitatdistributions of X. conformis and X. ramesisKey words. Meriones crassus, Xenopsylla conformis, X. ramesis, developmentrate, eggs, females, jird, larvae, males, pupae, relative humidity, temperature,Negev, Israel.
Tom G Schwan - One of the best experts on this subject based on the ideXlab platform.
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effect of yersinia pestis infection on temperature preference and movement of the oriental rat flea Xenopsylla cheopis siphonaptera pulicidae
Journal of Medical Entomology, 1993Co-Authors: Rex E Thomas, Robert H Karstens, Tom G SchwanAbstract:Previous laboratory studies have shown that inoculation of bacterial endotoxin into the hemocoel of some arthropods, or natural infection by a number of pathogens, causes them to seek out a higher ambient temperature. This phenomenon has been called behavioral fever. Yersinia pestis is an endotoxin-producing bacterium that relies on infection of fleas for transmission. Behavioral fever in fleas might enhance the transmission of plague if infected fleas were induced to seek out a warm-bodied host after the death of an infected host. Our study indicates that in thermal gradients Y. pestis infected Oriental rat fleas (Xenopsylla cheopis) do not exhibit behavioral fever and in one experiment sought out a significantly lower temperature.
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Xenopsylla bantorum is an east african subspecies of x cheopis siphonaptera pulicidae
Journal of Medical Entomology, 1992Co-Authors: Tom G SchwanAbstract:The geographic distribution, host association, and male genital morphology of Xenopsylla bantorum Jordan were examined and compared with the Nilotic and Oriental “strains” of Xenopsylla cheopis (Rothschild). The more acute shape of the ninth sternite separates X. bantorum from all types of X. cheopis; however, the length of the first process of the male's clasper and the number of setae on this process are significantly different among all three groups; the Nilotic strain of X. cheopis is intermediate to the others. Specimens collected from both wild and commensal rodents in Nakuru, Kenya, were all X. bantorum, suggesting that X. cheopis present early in the century that resulted from introductions on Rattus rattus had been absorbed by the native X. bantorum population. These factors and a review of opinions by others concerning the status of X. bantorum demonstrate that this flea is not specifically distinct from X. cheopis. The trinomial X. cheopis bantorum is erected. Furthermore, the Nilotic and Oriental “strains” of X. cheopis are distinguishable morphologically solely by the length of the male's first process.
Laura J Fielden - One of the best experts on this subject based on the ideXlab platform.
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water balance in two species of desert fleas Xenopsylla ramesis and x conformis siphonaptera pulicidae
Journal of Medical Entomology, 2002Co-Authors: Laura J Fielden, Boris R Krasnov, Kelly M Still, Irina S KhokhlovaAbstract:The role of water balance capabilities of seas was examined in desert habitats. The seas studied were Xenopsylla ramesis Rothschild and Xenopsylla conformis Wagner. Both seas occur on SundevallOs jird, Meriones crassus, in the Negev Highlands of Israel but in different macro- and microhabitats. Because M. crassus occurs in several habitats of the highlands, it was used as a model for investigating the effect of habitat parameters on species composition of seas within a host species. Water balance parameters investigated were the range of humidities over which active water uptake occurs in the larvae and prepupae of X. ramesis and X. conformis. Critical equilibrium humidity estimates were close to 65% RH for larvae and prepupae of both species. Water loss rates were determined for each life stage, except eggs, and represented water loss from cuticular, respiratory, and other body openings) under conditions of little or no bulk air movement. When converted to a proportional rate (1.44 Ð2.37% mass loss h 1 ) water loss rates did not differ signiÞcantly between stages or species. Thus, geographic separation of X. ramesis and X. conformis could not be explained by any difference in water uptake capabilities or water loss rates. Other factors that may be important include interspeciÞc competition for resource availability among larval seas and effect of soil texture on cocoon construction.
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development rates of two Xenopsylla flea species in relation to air temperature and humidity
Medical and Veterinary Entomology, 2001Co-Authors: Boris R Krasnov, Irina S Khokhlova, Laura J Fielden, Nadezhda V BurdelovaAbstract:Abstract. The rate of development of immature fleas, Xenopsylla conformisWagner and Xenopsylla ramesis Rothschild (Siphonaptera: Xenopsyllidae) wasstudied in the laboratory at 25°C and 28°C with 40, 55, 75 and 92% relativehumidity (RH). These fleas are separately associated with the host jird Merionescrassus Sundevall in different microhabitats of the Ramon erosion cirque, NegevHighlands, Israel. This study of basic climatic factors in relation to flea bionomicsprovides the basis for ecological investigations to interpret reasons for paratopiclocal distributions of these two species of congeneric fleas on the same host. Bothair temperature and RH were positively correlated with duration of egg and larvalstages in both species. Change of humidity between egg and larval environmentsdid not affect duration of larval development at any temperature. At eachtemperature and RH, the eggs and larvae of X. ramesis did not differ betweenmales and females in the duration of their development, whereas female eggs andlarvae of X. conformis usually developed significantly faster than those of males.For both species, male pupae developed slower than female pupae at the same airtemperature and RH. Air temperature, but not RH, affected the duration of pupaldevelopment. At each humidity, duration of the pupal stage was significantly longerat 25°C than at 28°C: 15.3 6 1.7 vs. 11.7 6 1.2 days in X. conformis; 14.1 6 2.0vs. 11.5 6 1.7 days in X. ramesis, with a significantly shorter pupal period of thelatter species at 25°C. These limited interspecific bionomic contrasts in relation tobasic climatic factors appear insufficient to explain the differential habitatdistributions of X. conformis and X. ramesisKey words. Meriones crassus, Xenopsylla conformis, X. ramesis, developmentrate, eggs, females, jird, larvae, males, pupae, relative humidity, temperature,Negev, Israel.
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respiratory gas exchange in the flea Xenopsylla conformis siphonaptera pulicidae
Journal of Medical Entomology, 2001Co-Authors: Laura J Fielden, Boris R Krasnov, Irina S KhokhlovaAbstract:Respiratory gas exchange was measured in various developmental stages of the flea Xenopsylla conformis mycerini (Rothschild, 1904) originating from the central Negev in Israel. Gas exchange in fleas was measured using a flow-through respirometry system that monitored CO2 emission. Lowest metabolic rates were found in the cocooned stage, which included prepupae, early stage pupae, late stage pupae, and preemerged adults. Newly emerged adults and feeding larvae had metabolic rates 2.5–3.0 times greater than those for the cocooned stages. Highest rates of gas exchange were found in feeding fleas. The low metabolic rates of the cocooned stages is thought to contribute to their ability to survive for longer periods than free-living larvae and adults.
Yajun Song - One of the best experts on this subject based on the ideXlab platform.
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transmission efficiency of the plague pathogen y pestis by the flea Xenopsylla skrjabini to mice and great gerbils
Parasites & Vectors, 2015Co-Authors: Yujiang Zhang, Qiguo Wang, Hongjian Chen, Weiwei Meng, Kemei Wu, Xinhui Wang, Azhati Rehemu, Xiaotao Yu, Ruifu Yang, Yajun SongAbstract:Background Plague, a zoonotic disease caused by Yersinia pestis, is characterized by its ability to persist in the plague natural foci. Junggar Basin plague focus was recently identified in China, with Rhombomys opimus (great gerbils) and Xenopsylla skrjabini as the main reservoir and vector for plague. No transmission efficiency data of X. skrjabini for Y. pestis is available till now.
