Gametocyte sex ratio in single-clone infections of the malaria parasite Plasmodium mexicanum

Parasitology ◽  
2010 ◽  
Vol 137 (13) ◽  
pp. 1851-1859 ◽  
Author(s):  
A.T. NEAL ◽  
J.J. SCHALL
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Malaria Parasite ◽  
Sex Ratios ◽  
Experimental Studies ◽  
Life History Trait ◽  
Gametocyte Density ◽  
Male Gametes ◽  
Single Clone ◽  
Sex Ratio Theory

SUMMARYSex ratio theory predicts that malaria parasites should bias gametocyte production toward female cells in single-clone infections because they will experience complete inbreeding of parasite gametes within the vector. A higher proportion of male gametocytes is favoured under conditions that reduce success of male gametes at reaching females such as low gametocyte density or attack of the immune system later in the infection. Recent experimental studies reveal genetic variation for gametocyte sex ratio in single-clone infections. We examined these issues with a study of experimental single-clone infections for the lizard malaria parasite Plasmodium mexicanum in its natural host. Gametocyte sex ratios of replicate single-clone infections were determined over a period of 3–4 months. Sex ratios were generally female biased, but not as strongly as expected under simple sex ratio theory. Gametocyte density was not related to sex ratio, and male gametocytes did not become more common later in infections. The apparent surplus of male gametocytes could be explained if male fecundity is low in this parasite, or if rapid clotting of the lizard blood reduces male gamete mobility. There was also a significant clone effect on sex ratio, suggesting genetic variation for some life-history trait, possibly male fecundity.

Male gametocyte fecundity and sex ratio of a malaria parasite, Plasmodium mexicanum

Parasitology ◽  
2011 ◽  
Vol 138 (10) ◽  
pp. 1203-1210 ◽  
Author(s):  
A. T. NEAL
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Evolutionary Theory ◽  
Malaria Parasite ◽  
Clonal Diversity ◽  
Male Gametes ◽  
A Value ◽  
Parasite Plasmodium ◽  
Sex Ratio Theory ◽  
Few Data

SUMMARYEvolutionary theory predicts that the sex ratio of Plasmodium gametocytes will be determined by the number of gametes produced per male gametocyte (male fecundity), parasite clonal diversity and any factor that reduces male gametes' ability to find and combine with female gametes. Despite the importance of male gametocyte fecundity for sex ratio theory as applied to malaria parasites, few data are available on gamete production by male gametocytes. In this study, exflagellating gametes, a measure of male fecundity, were counted for 866 gametocytes from 26 natural infections of the lizard malaria parasite, Plasmodium mexicanum. The maximum male fecundity observed was 8, but most gametocytes produced 2–3 gametes, a value consistent with the typical sex ratio observed for P. mexicanum. Male gametocytes in infections with higher gametocytaemia had lower fecundity. Male fecundity was not correlated with gametocyte size, but differed among infections, suggesting genetic variation for fecundity. Fecundity and sex ratio were correlated (more female gametocytes with higher fecundity) as predicted by theory. Results agree with evolutionary theory, but also suggest a possible tradeoff between production time and fecundity, which could explain the low fecundity of this species, the variation among infections, and the correlation with gametocytaemia.

scholarly journals Sex ratios in the rodent malaria parasite, Plasmodium chabaudi

Parasitology ◽  
2003 ◽  
Vol 127 (5) ◽  
pp. 419-425 ◽  
Author(s):  
S. E. REECE ◽  
A. B. DUNCAN ◽  
S. A. WEST ◽  
A. F. READ
Keyword(s):  
Mortality Rate ◽  
Sex Ratio ◽  
Malaria Parasite ◽  
Sex Ratios ◽  
Plasmodium Chabaudi ◽  
Rodent Malaria Parasite ◽  
Malaria Parasites ◽  
Rodent Malaria ◽  
Sex Ratio Theory

The sex ratios of malaria and related Apicomplexan parasites play a major role in transmission success. Here, we address 2 fundamental issues in the sex ratios of the rodent malaria parasite, Plasmodium chabaudi. First we test the accuracy of empirical methods for estimating sex ratios in malaria parasites, and show that sex ratios made with standard thin smears may overestimate the proportion of female gametocytes. Secondly, we test whether the mortality rate differs between male and female gametocytes, as assumed by sex ratio theory. Conventional application of sex ratio theory to malaria parasites assumes that the primary sex ratio can be accurately determined from mature gametocytes circulating in the peripheral circulation. We stopped gametocyte production with chloroquine in order to study a cohort of gametocytes in vitro. The mortality rate was significantly higher for female gametocytes, with an average half-life of 8 h for female gametocytes and 16 h for male gametocytes.

scholarly journals Consistent sex ratio bias of individual female dragon lizards

2006 ◽  
Vol 2 (4) ◽  
pp. 569-572 ◽  
Author(s):  
Tobias Uller ◽  
Beth Mott ◽  
Gaetano Odierna ◽  
Mats Olsson
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Incubation Temperature ◽  
Sex Ratios ◽  
Phenotypic Traits ◽  
Female Size ◽  
Offspring Sex Ratio ◽  
Phenotypic Differences ◽  
Sex Ratio Bias ◽  
Offspring Sex

Sex ratio evolution relies on genetic variation in either the phenotypic traits that influence sex ratios or sex-determining mechanisms. However, consistent variation among females in offspring sex ratio is rarely investigated. Here, we show that female painted dragons ( Ctenophorus pictus ) have highly repeatable sex ratios among clutches within years. A consistent effect of female identity could represent stable phenotypic differences among females or genetic variation in sex-determining mechanisms. Sex ratios were not correlated with female size, body condition or coloration. Furthermore, sex ratios were not influenced by incubation temperature. However, the variation among females resulted in female-biased mean population sex ratios at hatching both within and among years.

Estimating the Frequency of Constrained Sex Allocation in Field Populations of Hymenoptera

Behaviour ◽  
1990 ◽  
Vol 114 (1-4) ◽  
pp. 137-147 ◽  
Author(s):  
H.C.J. Godfray ◽  
I.C.W. Hardy
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Parasitoid Species ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Sex Ratio Theory

Abstract1) Sex ratio theory has assumed that females can produce offspring of both sexes. It has been suggested that some females in haplodiploid populations are only able to produce sons (constrained sex allocation), for example because they are virgin. The presence of such females influences the optimal sex ratio of unconstrained females. The relevance of these ideas to field sex ratios is largely untested. 2) The frequencies of constrained oviposition in three Drosophila parasitoid species are estimated. Constrained, ovipositing females were distinguished by the absence of sperm in the spermatheca. Constrained females were absent or rare in these species. 3) We review data from the literature that allow an estimate of the frequency of constrained females. 4) We conclude that the available evidence suggests that while constrained oviposition is uncommon, there are some species in which constrained females are sufficiently common to select for an observable sex ratio bias by unconstrained females.

scholarly journals Extraordinarily precise nematode sex ratios: Adaptive responses to vanishingly rare mating options

2021 ◽  
Author(s):  
Justin Van Goor ◽  
Edward Allen Herre ◽  
Adalberto Gomez ◽  
John D Nason
Keyword(s):  
Sex Ratio ◽  
Sex Ratios ◽  
Nematode Species ◽  
Environmental Sex Determination ◽  
Adaptive Responses ◽  
Wasp Species ◽  
Population Structures ◽  
Subdivided Populations ◽  
Sex Ratio Theory ◽  
Evolutionary Persistence

Sex ratio theory predicts both mean sex ratio and variance under a range of population structures. Here, we compare two genera of phoretic nematodes (Parasitodiplogaster and Ficophagus spp.) associated with twelve fig-pollinating wasp species in Panama. The host wasps exhibit classic Local Mate Competition: only inseminated females disperse from natal figs, and their offspring form mating pools that consist of scores of the adult offspring contributed by one or a few foundress mothers. In contrast, in both nematode genera, only sexually undifferentiated juveniles disperse, and their mating pools routinely consist of eight or fewer adults. Across all mating pool sizes, the sex ratios observed in both nematode genera are consistently female-biased (~0.34 males), which is markedly less female-biased than is often observed in the host wasps (~0.10 males). In further contrast with their hosts, variances in nematode sex ratios are also consistently precise (significantly less than binomial). The constraints associated with predictably small mating pools within highly subdivided populations appear to select for precise sex ratios that contribute both to the reproductive success of individual nematodes, and to the evolutionary persistence of nematode species. We suggest that some form of environmental sex determination underlies these precise sex ratios.

Gametocyte sex ratio of a malaria parasite: response to experimental manipulation of parasite clonal diversity

Parasitology ◽  
2004 ◽  
Vol 128 (1) ◽  
pp. 23-29 ◽  
Author(s):  
S. M. OSGOOD ◽  
J. J. SCHALL
Keyword(s):  
Sex Ratio ◽  
Malaria Parasite ◽  
Clonal Diversity ◽  
Experimental Manipulation ◽  
Sceloporus Occidentalis ◽  
Infected Blood ◽  
Single Donor ◽  
Mixed Blood ◽  
Sex Ratio Theory ◽  
Male To Female

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 with infected blood from a single donor or 3 pooled donors. Donors varied in their gametocyte sex ratios (17–46% male), and sex ratio theory allowed estimation of the clonal diversity within donor and recipient infections. Phenotypic plasticity would produce a correlation between donor and recipient infections for infections initiated from a single donor, and a less female-biased gametocyte sex ratio in recipients that received a mixed blood inoculum (with predicted higher clonal diversity) than recipients receiving blood from a single donor. Neither pattern was observed. Gametocyte sex ratio of most infections ranged from 35 to 42% male, expected if clonal diversity was high for all infections. Alternative explanations are suggested for the observed variation of gametocyte sex ratio among P. mexicanum infections.

scholarly journals GENETIC VARIATION FOR THE SEX RATIO IN NASONIA VITRIPENNIS

Genetics ◽  
1985 ◽  
Vol 110 (1) ◽  
pp. 93-105
Author(s):  
E Davis Parker ◽  
Steven Hecht Orzack
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Artificial Selection ◽  
Sex Ratios ◽  
Female Parent ◽  
Parasitoid Wasp ◽  
Selection Response ◽  
Inbred Lines ◽  
Selection Experiment ◽  
Nasonia Vitripennis

ABSTRACT We detected genetic variation for the sex ratio in the parasitoid wasp Nasonia vitripennis by analysis of inbred lines and with an artificial selection experiment. Sex ratios differed significantly among five independently isolated lines. Furthermore, sex ratio in broods produced by single females in single hosts shifted from 80-90% female to 50-55% female in 13 to 15 generations in each of two replicate selection lines. The final sex ratios of both selection lines were significantly lower than any of the inbred line sex ratios. Backcrosses revealed that the selection response was due to nuclear genes acting through the female parent. In light of known facultative sex ratio behavior and major genes affecting sex ratio in Nasonia, our results suggest that population and individual sex ratios in this species are molded by processes at both genetic and behavioral levels.

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