| life history of a malaria parasite (plasmodium mexicanum) in its host, the western fence lizard (sceloporus occidentalis): host testosterone as a source of seasonal and among-host variation? | the course of infection of a malaria parasite (plasmodium mexicanum) is highly variable in its host, the fence lizard (sceloporus occidentalis). however, a seasonal trend is superimposed on this variation such that gametocyte production is intensified during mid- to late summer. host testosterone levels follow a similar seasonal fluctuation and are variable among individual lizards. we sought to determine if testosterone levels affect seasonal and among-host variation in 11 p. mexicanum life his ... | 2000 | 11128477 |
| gametocyte sex ratio of a malaria parasite: experimental test of heritability. | the gametocyte sex ratio of plasmodium mexicanum, a malaria parasite of western fence lizards, was studied in a modified garden experiment. each of 6 naturally infected lizards was used to initiate 20 replicate-infections in naive western fence lizards. a significant donor effect was observed for the sex ratios of recipient infections at their maximal parasitemia, and this effect was associated with the sex ratio of the donor infection. in 20 infections in which sex ratio was followed during the ... | 2002 | 12099417 |
| absence of measurable malaria-induced mortality in western fence lizards (sceloporus occidentalis) in nature: a 4-year study of annual and over-winter mortality. | theoretical models of parasite virulence often quantify virulence by mortality. however, there is a lack of empirical studies of parasite-induced host mortality because it is often difficult to quantify in natural populations. i have estimated annual and over-winter mortality in a population of fence lizards (sceloporus occidentalis) infected with a malaria parasite, plasmodium mexicanum, in northern california. the duration of time a lizard was observed (an estimate of life-span) throughout the ... | 2001 | 28547496 |
| the occurrence and development of plasmodium mexicanum in the western fence lizard sceloporus occidentalis. | | 1970 | 5420333 |
| parasites and showy males: malarial infection and color variation in fence lizards. | hamilton and zuk (1982) proposed that the quality of male showy traits reflects genetically-based resistance to parasites and can be used by females to select mates that are less prone to parasitic attack. the hypothesis requires that a particular state of a variable showy trait should be associated with parasite infection. we tested this idea with a population of western fence lizards, sceloporus occidentalis, infected with the malarial parasite, plasmodium mexicanum. ventral color pattern is s ... | 1989 | 28312354 |
| relative clonal proportions over time in mixed-genotype infections of the lizard malaria parasite plasmodium mexicanum. | vertebrate hosts of malaria parasites (plasmodium) often harbour two or more genetically distinct clones of a single species, and interaction among these co-existing clones can play an important role in plasmodium biology. however, how relative clonal proportions vary over time in a host is still poorly known. experimental mixed-clone infections of the lizard malaria parasite, plasmodium mexicanum, were followed in its natural host, the western fence lizard using microsatellite markers to determ ... | 2011 | 21396372 |
| geographic genetic differentiation of a malaria parasite, plasmodium mexicanum, and its lizard host, sceloporus occidentalis. | gene flow, and resulting degree of genetic differentiation among populations, will shape geographic genetic patterns and possibly local adaptation of parasites and their hosts. some studies of plasmodium falciparum in humans show substantial differentiation of the parasite in locations separated by only a few kilometers, a paradoxical finding for a parasite in a large, mobile host. we examined genetic differentiation of the malaria parasite plasmodium mexicanum, and its lizard host, sceloporus o ... | 2010 | 19916631 |
| clonal diversity of a malaria parasite, plasmodium mexicanum, and its transmission success from its vertebrate-to-insect host. | infections of the lizard malaria parasite plasmodium mexicanum are often genetically complex within their fence lizard host (sceloporus occidentalis) harbouring two or more clones of parasite. the role of clonal diversity in transmission success was studied for p. mexicanum by feeding its sandfly vectors (lutzomyia vexator and lutzomyia stewarti) on experimentally infected lizards. experimental infections consisted of one, two, three or more clones, assessed using three microsatellite markers. a ... | 2009 | 19523471 |
| clonal diversity within infections and the virulence of a malaria parasite, plasmodium mexicanum. | both verbal and mathematical models of parasite virulence predict that genetic diversity of microparasite infections will influence the level of costs suffered by the host. we tested this idea by manipulating the number of co-existing clones of plasmodium mexicanum in its natural vertebrate host, the fence lizard sceloporus occidentalis. we established replicate infections of p. mexicanum made up of 1, 2, 3, or >3 clones (scored using 3 microsatellite loci) to observe the influence of clone numb ... | 2008 | 18937882 |
| malarial parasitism and male competition for mates in the western fence lizard, sceloporus occidentalis. | the effect of malarial parasitism on the ability of male western fence lizards, sceloporus occidentalis, to compete for access to females was assessed experimentally. pairs of male lizards, one infected with the malarial parasite, plasmodium mexicanum, and the other not infected, were matched by size and color and placed in large seminatural outdoor enclosures along with an adult female lizard. infected males displayed to females and to other males less often than did noninfected male lizards. n ... | 1987 | 28311520 |
| experimental test for premunition in a lizard malaria parasite (plasmodium mexicanum). | premunition in plasmodium spp. is the prevention of superinfection by novel genotypes entering an already established infection in a vertebrate host. evidence for premunition was sought for the lizard malaria parasite, p. mexicanum, in its natural host, the fence lizard, sceloporus occidentalis. clonal diversity (= alleles for the haploid parasite) was determined with the use of 3 microsatellite markers. both naturally infected lizards (n = 25) and previously noninfected lizards (n = 78) were in ... | 2007 | 17539410 |
| multiple environmental stressors elicit complex interactive effects in the western fence lizard (sceloporus occidentalis). | evaluation of multiple-stressor effects stemming from habitat degradation, climate change, and exposure to chemical contaminants is crucial for addressing challenges to ecological and environmental health. to assess the effects of multiple stressors in an understudied taxon, the western fence lizard (sceloporus occidentalis) was used to characterize the individual and combined effects of food limitation, exposure to the munitions constituent 2,4,6-trinitrotoluene (tnt), and plasmodium mexicanum ... | 2012 | 22975894 |
| manipulation of the vertebrate host's testosterone does not affect gametocyte sex ratio of a malaria parasite. | gametocyte sex ratio of the malaria parasite plasmodium mexicanum is variable in its host, the western fence lizard (sceloporus occidentalis), both among infections and within infections over time. we sought to determine the effect of host physiological quality on the gametocyte sex ratio in experimentally induced infections of p. mexicanum. adult male lizards were assigned to 4 treatment groups: castrated, castrated + testosterone implant, sham implant, and unmanipulated control. no significant ... | 2003 | 12659329 |
| landscape features associated with infection by a malaria parasite (plasmodium mexicanum) and the importance of multiple scale studies. | in a 3-year study, we examined landscape features (aspect, slope, sun exposure, canopy cover, type of ground cover, and nearest water source) that were potentially related to prevalence of infection with plasmodium mexicanum in fence lizards (sceloporus occidentalis) within a 4.5 ha study area in northern california, usa. logistic regression analysis showed that ground cover type was the primary mediator of the probability of p. mexicanum infection. infected lizards were captured more often in r ... | 2001 | 11393823 |
| lizards infected with malaria: physiological and behavioral consequences. | in northern california, western fence lizards, sceloporus occidentalis, are frequently parasitized by plasmodium mexicanum, which causes malaria. animals with this naturally occurring malarial infection are anemic: immature erythrocytes in peripheral blood become abundant (1 to 30 percent), and blood hemoglobin concentration decreases 25 percent. maximal oxygen consumption decreases 15 percent and aerobic scope drops 29 percent in infected lizards; both correlate with blood hemoglobin concentrat ... | 1982 | 7112113 |
| leukocyte profiles for western fence lizards, sceloporus occidentalis, naturally infected by the malaria parasite plasmodium mexicanum. | plasmodium mexicanum is a malaria parasite that naturally infects the western fence lizard, sceloporus occidentalis , in northern california. we set out to determine whether lizards naturally infected with this malaria parasite have different leukocyte profiles, indicating an immune response to infection. we used 29 naturally infected western fence lizards paired with uninfected lizards based on sex, snout-to-vent length, tail status, and the presence-absence of ectoparasites such as ticks and m ... | 2014 | 24945903 |
| clonal diversity of a lizard malaria parasite, plasmodium mexicanum, in its vertebrate host, the western fence lizard: role of variation in transmission intensity over time and space. | within the vertebrate host, infections of a malaria parasite (plasmodium) could include a single genotype of cells (single-clone infections) or two to several genotypes (multiclone infections). clonal diversity of infection plays an important role in the biology of the parasite, including its life history, virulence, and transmission. we determined the clonal diversity of plasmodium mexicanum, a lizard malaria parasite at a study region in northern california, using variable microsatellite marke ... | 2007 | 17594442 |
| gametocyte sex ratio of a malaria parasite: response to experimental manipulation of parasite clonal diversity. | sex ratio theory posits that the adaptive proportion of male to female gametocytes of a malaria parasite within the vertebrate host depends on the degree of inbreeding within the vector. gametocyte sex ratio could be phenotypically flexible, being altered based on the infection's clonal diversity, and thus likely inbreeding. this idea was tested by manipulating the clonal diversity of infections of plasmodium mexicanum in its lizard host, sceloporus occidentalis. naive lizards were inoculated wi ... | 2004 | 15002900 |
| the sex ratio of plasmodium gametocytes. | sex ratio theory usually predicts an equilibrium sex ratio and equal proportions of males and females in a population, including the progenitors of the reproductive cells of protozoans. this proposal was tested with three species of malarial parasites of lizards, plasmodium mexicanum of the western fence lizard, and p. agamae and p. giganteum of the african rainbow lizard, using single samples from naturally infected lizards, repeated samples from free-ranging lizards (p. mexicanum only), and re ... | 1989 | 2771445 |