The ecology and evolution of microsporidian parasites

Parasitology ◽  
2009 ◽  
Vol 136 (14) ◽  
pp. 1901-1914 ◽  
Author(s):  
J. E. SMITH
Keyword(s):  
Phylogenetic Analysis ◽  
Life Cycle ◽  
Sex Ratio ◽  
Vertical Transmission ◽  
Environmental Risk ◽  
Disease Phenotype ◽  
Life Cycle Stages ◽  
Wide Range ◽  
Ratio Distortion ◽  
Sex Ratio Distortion

SUMMARYThe phylum Microspora is ancient and diverse and affects a wide range of hosts. There is unusually high use of vertical transmission and this has significant consequences for transmission and pathogenicity. Vertical transmission is associated with low pathogenesis but nevertheless can have significant impact through associated traits such as sex ratio distortion. The majority of microsporidia have mixed transmission cycles and it is not clear whether they are able to modify their phenotype according to environmental circumstances. There is a great need to understand the mechanisms controlling transmission and one of the first challenges for the genomics era is to find genes associated with life cycle stages. Similarly we cannot currently predict the ease with which these parasites might switch between host groups. Phylogenetic analysis suggests that there are strong relationships between Microsporidia and their hosts. However closer typing of parasite isolates, in relation to host range and disease phenotype, is required to assess future environmental risk from these pathogens.

scholarly journals Widespread vertical transmission and associated host sex–ratio distortion within the eukaryotic phylum Microspora

2004 ◽  
Vol 271 (1550) ◽  
pp. 1783-1789 ◽  
Author(s):  
Rebecca S. Terry ◽  
Judith E. Smith ◽  
Rosie G. Sharpe ◽  
Thierry Rigaud ◽  
D. Timothy J. Littlewood ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Vertical Transmission ◽  
Host Sex ◽  
Ratio Distortion ◽  
Sex Ratio Distortion

scholarly journals Sex Ratios in a Warming World: Thermal Effects on Sex-Biased Survival, Sex Determination, and Sex Reversal

2021 ◽  
Vol 112 (2) ◽  
pp. 155-164
Author(s):  
Suzanne Edmands
Keyword(s):  
High Temperature ◽  
Sex Ratio ◽  
Sex Determination ◽  
Heat Tolerance ◽  
Sex Ratios ◽  
Sex Reversal ◽  
Survival Sex ◽  
Ratio Distortion ◽  
Warming World ◽  
Sex Ratio Distortion

Abstract Rising global temperatures threaten to disrupt population sex ratios, which can in turn cause mate shortages, reduce population growth and adaptive potential, and increase extinction risk, particularly when ratios are male biased. Sex ratio distortion can then have cascading effects across other species and even ecosystems. Our understanding of the problem is limited by how often studies measure temperature effects in both sexes. To address this, the current review surveyed 194 published studies of heat tolerance, finding that the majority did not even mention the sex of the individuals used, with <10% reporting results for males and females separately. Although the data are incomplete, this review assessed phylogenetic patterns of thermally induced sex ratio bias for 3 different mechanisms: sex-biased heat tolerance, temperature-dependent sex determination (TSD), and temperature-induced sex reversal. For sex-biased heat tolerance, documented examples span a large taxonomic range including arthropods, chordates, protists, and plants. Here, superior heat tolerance is more common in females than males, but the direction of tolerance appears to be phylogenetically fluid, perhaps due to the large number of contributing factors. For TSD, well-documented examples are limited to reptiles, where high temperature usually favors females, and fishes, where high temperature consistently favors males. For temperature-induced sex reversal, unambiguous cases are again limited to vertebrates, and high temperature usually favors males in fishes and amphibians, with mixed effects in reptiles. There is urgent need for further work on the full taxonomic extent of temperature-induced sex ratio distortion, including joint effects of the multiple contributing mechanisms.

scholarly journals Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1169-1180 ◽  
Author(s):  
Daven C Presgraves ◽  
Emily Severance ◽  
Gerald S Willrinson
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Operational Sex Ratio ◽  
Genetic Modifiers ◽  
Ratio Distortion ◽  
The Impact ◽  
Sex Ratio Distortion

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (Xd). Relatively high frequencies of Xd in C. dalmanni and C. whitei (13–17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of Xd. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with Xd, modifying Y chromosomes (Ym) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of Xd on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.

scholarly journals Genetics and Genomics of an Unusual Selfish Sex Ratio Distortion in an Insect

2018 ◽  
Vol 28 (23) ◽  
pp. 3864-3870.e4 ◽  
Author(s):  
Phineas T. Hamilton ◽  
Christina N. Hodson ◽  
Caitlin I. Curtis ◽  
Steve J. Perlman
Keyword(s):  
Sex Ratio ◽  
Ratio Distortion ◽  
Genetics And Genomics ◽  
Sex Ratio Distortion

scholarly journals Endocrine Control of Life-Cycle Stages: A Constraint on Response to the Environment?

The Condor ◽  
2000 ◽  
Vol 102 (1) ◽  
pp. 35-51 ◽  
Author(s):  
Jerry D. Jacobs ◽  
John C. Wingfield
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Control Systems ◽  
Life Cycles ◽  
Environmental Cues ◽  
Endocrine Control ◽  
Theoretical Approaches ◽  
Life Cycle Stages ◽  
Wide Range ◽  
Breeding Seasons

Abstract Most organisms live in seasonal environments that fluctuate on a predictable schedule and sometimes unpredictably. Individuals must, therefore, adjust so as to maximize their survival and reproductive success over a wide range of environmental conditions. In birds, as in other vertebrates, endocrine secretions regulate morphological, physiological, and behavioral changes in anticipation of future events. The individual thus prepares for predictable fluctuations in its environment by changing life-cycle stages. We have applied finite-state machine theory to define and compare different life-history cycles. The ability of birds to respond to predictable and unpredictable regimes of environmental variation may be constrained by the adaptability of their endocrine control systems. We have applied several theoretical approaches to natural history data of birds to compare the complexity of life cycles, the degree of plasticity of timing of stages within the cycle, and to determine whether endocrine control mechanisms influence the way birds respond to their environments. The interactions of environmental cues on the timing of life-history stages are not uniform in all populations. Taking the reproductive life-history stage as an example, arctic birds that have short breeding seasons in severe environments appear to use one reliable environmental cue to time reproduction and they ignore other factors. Birds having longer breeding seasons exhibit greater plasticity of onset and termination and appear to integrate several environmental cues. Theoretical approaches may allow us to predict how individuals respond to their environment at the proximate level and, conversely, predict how constraints imposed by endocrine control systems may limit the complexity of life cycles.

Photographic polytene chromosome maps for Glossina morsitans submorsitans (Diptera: Glossinidae): cytogenetic analysis of a colony with sex-ratio distortion

Genome ◽  
2002 ◽  
Vol 45 (5) ◽  
pp. 871-880 ◽  
Author(s):  
A Gariou-Papalexiou ◽  
G Yannopoulos ◽  
A Zacharopoulou ◽  
R H Gooding
Keyword(s):  
Sex Ratio ◽  
Polytene Chromosome ◽  
X Chromosome ◽  
Polytene Chromosomes ◽  
Glossina Morsitans ◽  
Glossina Morsitans Submorsitans ◽  
Ratio Distortion ◽  
Chromosome Maps ◽  
Sex Ratio Distortion ◽  
Pharate Adult

Photographic polytene chromosome maps from trichogen cells of pharate adult Glossina morsitans submorsitans were constructed. Using the standard system employed to map polytene chromosomes of Drosophila, the characteristic landmarks were described for the X chromosome and the two autosomes (L1 and L2). Sex-ratio distortion, which is expressed in male G. m. submorsitans, was found to be associated with an X chromosome (XB) that contains three inversions in each arm. Preliminary data indicate no differences in the fecundity of XAXA and XAXB females, but there are indications that G. m. submorsitans in colonies originating from Burkina Faso and Nigeria have genes on the autosomes and (or) the Y chromosome that suppress expression of sex-ratio distortion.Key words: tsetse, Glossina morsitans submorsitans, polytene chromosome maps, inversions, sex-ratio distortion.

Tetracycline treatment and sex-ratio distortion: a role for Wolbachia in the moulting of filarial nematodes?

2002 ◽  
Vol 32 (12) ◽  
pp. 1457-1468 ◽  
Author(s):  
M Casiraghi ◽  
J.W McCall ◽  
L Simoncini ◽  
L.H Kramer ◽  
L Sacchi ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Filarial Nematodes ◽  
Ratio Distortion ◽  
Tetracycline Treatment ◽  
Sex Ratio Distortion

scholarly journals Publisher Correction: Introgression of a synthetic sex ratio distortion system from Anopheles gambiae into Anopheles arabiensis

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Federica Bernardini ◽  
Antonios Kriezis ◽  
Roberto Galizi ◽  
Tony Nolan ◽  
Andrea Crisanti
Keyword(s):  
Sex Ratio ◽  
Anopheles Gambiae ◽  
Anopheles Arabiensis ◽  
Ratio Distortion ◽  
Sex Ratio Distortion
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