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Sex ratio and morphological characteristics of rufous gnateaters, Conopophaga lineata (Aves, Passeriformes) in Atlantic forest fragments; Razão sexual e características morfológicas do chupa-dente, Conopophaga lineata (Aves, Passeriformes) em fragmentos da Mata Atlântica

DANTAS, Gisele P. M.; SANTOS, Fabrício R.; MARINI, Miguel Ângelo
Fonte: Fundação Zoobotânica do Rio Grande do Sul Publicador: Fundação Zoobotânica do Rio Grande do Sul
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.2%
Unequal sex ratios lead to the loss of genetic variability, decreasing the viability of populations in the long term. Anthropogenic activities often disturb the natural habitats and can cause alterations in sex ratio and morphological characteristics of several species. Forest fragmentation is a major conservation concern, so that understanding its effects in natural populations is essential. In this study, we evaluated the sex ratio and the morphological characteristics of Rufous Gnateaters (Conopophaga lineata (Wied, 1831)) in small and large forest fragments in Minas Gerais, Brazil. Birds (n = 89) were sexed by plumage characteristics and molecular markers. The molecular analysis showed that plumage is not a totally reliable method for sexing Rufous Gnateaters. We observed that sex ratio did not differ between large and small forest fragments, but birds in small fragments had larger wings and tarsus. Wing and tarsus changes may affect the movement ability of individuals within and among forest fragments. In conclusion, Rufous Gnateaters have been able to survive in both small and large Atlantic rain forest fragments without altering their sex ratio, but morphological changes can be prejudicial to their long term survival.; A razão sexual desigual pode levar à perda de variabilidade genética...

Sex ratio and morphological characteristics of Rufous Gnateaters, Conopophaga lineata (Aves, Passeriformes) in Atlantic forest fragments

DANTAS, Gisele P. M.; SANTOS, Fabricio R.; MARINI, Miguel Angelo
Fonte: FUNDACAO ZOOBOTANICA RIO GRANDE SUL, MUSEU CIENCIAS NATURAIS Publicador: FUNDACAO ZOOBOTANICA RIO GRANDE SUL, MUSEU CIENCIAS NATURAIS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.2%
Unequal sex ratios lead to the loss of genetic variability, decreasing the viability of populations in the long term. Anthropogenic activities often disturb the natural habitats and can cause alterations in sex ratio and morphological characteristics of several species. Forest fragmentation is a major conservation concern, so that understanding its effects in natural populations is essential. In this study, we evaluated the sex ratio and the morphological characteristics of Rufous Gnateaters (Conopophaga lineata (Wied, 1831)) in small and large forest fragments in Minas Gerais, Brazil. Birds (n = 89) were sexed by plumage characteristics and molecular markers. The molecular analysis showed that plumage is not a totally reliable method for sexing Rufous Gnateaters. We observed that sex ratio did not differ between large and small forest fragments, but birds in small fragments had larger wings and tarsus. Wing and tarsus changes may affect the movement ability of individuals within and among forest fragments. In conclusion, Rufous Gnateaters have been able to survive in both small and large Atlantic rain forest fragments without altering their sex ratio, but morphological changes can be prejudicial to their long term survival.; CNPq; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

First molecular estimate of sex-ratio of southern right whale calves, Eubalaena australis, for Brazilian waters

OLIVEIRA, Larissa Rosa De; OTT, Paulo Henrique; FLORES, Paulo A. C.; SICILIANO, Salvatore; ALMEIDA, Raquel Santos De; BONATTO, Sandro L.
Fonte: CAMBRIDGE UNIV PRESS Publicador: CAMBRIDGE UNIV PRESS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.23%
The southern right whale (Eubalaena australis) was one of the most intensively hunted whales between the 17th and 20th centuries in the southern hemisphere. Recent estimates indicate that today there are around 7000 whales, representing 5 to 10% Of its original population. On the other hand, recent studies estimated that the population that migrates to the Brazilian coast grew by 14% from 1987 to 2003. However, there is no information about sex-ratio for adults or for calves in this region, which is an important parameter for understanding the biology of the species. We present here the first estimate Of calves` sex-ratio of southern right whales found along the southern Brazilian coast, one of the most important wintering grounds for the species. Sex was molecularly indentified for 21 biopsies collected from calves between 1998 and 2002, along the coast of Rio Grande do Sul and Santa Catarina States, in southern Brazil. The sex-ratio was two females for one male, however, it was not statistically different (chi(2) test, alpha = 0.05; df = 1) from the expected ratio of 1:1. This result is in accordance with the sex-ratio estimated for the species of all ages using external morphology (and behaviour in formation), (is well as for most species of baleen whales.; International Wildlife Coalition; International Wildlife Coalition; World Wildlife Fund (WWF-Brazil)[CSR 140-00]; World Wide Fund for Nature (WWF); Yaqu Pacha Foundation; Yaqu Pacha Foundation; CAPES (Ministry of Education...

Associação entre os níveis ambientais de poluição atmosférica e mudanças na razão sexual na cidade de São Paulo: uma abordagem epidemiológica e experimental; Association between ambient levels of air pollution and changes in the sex ratio in the city of "São Paulo" an epidemiologic and experimental approach

Lichtenfels, Ana Júlia de Faria Coimbra
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/10/2006 PT
Relevância na Pesquisa
66.21%
Prévios estudos têm demonstrado alterações nas taxas normais de razão sexual. No entanto, uma associação direta entre níveis ambientais de poluição e razão sexual, não tem sido ainda claramente demonstrada. A fim de investigarmos esta associação, desenvolvemos duas abordagens: uma epidemiológica e outra experimental. O efeito da poluição sobre a população da cidade de São Paulo foi verificado através da associação entre a razão sexual e gradientes de concentração de material particulado (PM10). A fim de conferir plausibilidade biológica aos achados epidemiológicos, camundongos machos com 10 dias de vida, foram expostos em câmaras do tipo Topo Aberto, sob condições de exposição mais controladas. Uma associação negativa e significante foi observada entre razão sexual e PM10, dentro de uma faixa estreita de concentração de PM10 (31 a 61 ?g/m3). Na região menos poluída, a razão sexual foi de 51,7% (106,8) para 34.795 nascimentos registrados, enquanto que para a mais poluída, a proporção decresceu para 50,7% (102,9) para 48.023 nascimentos registrados, com uma redução de 1% no número total de nascimentos masculinos. O grupo de camundongos da linhagem Swiss, acasalados com fêmeas virgens, maduras e não expostas...

Avaliação da Proporção Sexual de Embriões Desenvolvidos In Vitro e de Progênie a Campo de Touros Jovens.; Evaluation of the Sex Ratio of Embryos Developed In Vitro and in Field Progeny of Young Sires.

Elias, Fernanda Prado
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 01/08/2011 PT
Relevância na Pesquisa
66.19%
Um dos grandes problemas que afetam a produção in vitro de embriões é a variação entre touros em relação à fertilidade e o maior nascimento de embriões do sexo masculino. Muitos fatores podem alterar a razão de 1:1 entre os gêneros tanto na produção in vitro de embriões, como no método de Inseminação Artificial. No sentido de tentar alterar esta proporção sexual in vitro, estudamos em um primeiro momento, a variação entre touros no desenvolvimento de embriões machos e fêmeas, distribuídos nas fases de blastocisto jovem, blastocisto, blastocisto expandido e blastocisto eclodido, bem como, a proporção macho: fêmea em relação a fase do blastocisto. Para tanto, oócitos foram coletados de ovários oriundos de matadouro e maturados em meio de maturação em incubadora por 24h. Espermatozóides viáveis de 17 touros do Programa de Melhoramento Genético da Raça Nelore, obtidos por centrifugação em gradiente de Percoll, foram utilizados para Fecundação in vitro. Após 12h, os supostos zigotos foram cultivados em meio de cultivo e células do cumulus em incubadora. Ao sétimo dia após a fertilização in vitro foi feita a seleção dos blastocistos viáveis que foram sexados com a utilização de primers Y-específico bovino e autossômico bovino...

Sex ratio and dynamic behavior in populations of the exotic blowfly Chrysomya albiceps (Diptera, Calliphoridae)

Serra, H.; Godoy, W. A. C.; Von Zuben, F. J.; Von Zuben, C. J.; Reis, S. F.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: 347-353
ENG
Relevância na Pesquisa
66.24%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); A razão sexual é um componente essencial da biologia de organismos a ser considerado em crescimento populacional. Chrysomya albiceps é uma espécie de mosca varejeira que exibe um desvio na razão sexual em relação à proporção 1:1. Neste estudo avaliamos o impacto de alterações na razão sexual sobre o comportamento dinâmico de C. albiceps utilizando um modelo matemático dependente da densidade que incorpora parâmetros demográficos como sobrevivência e fecundidade. Os parâmetros foram obtidos por regressão exponencial, com sobrevivência e fecundidade sendo estimadas experimentalmente em função da densidade larval. O diagrama de bifurcação gerado pelos resultados indicou a evolução de pontos de equilíbrio estável em função da razão sexual. A sucessão contínua dos valores da razão sexual resultou em uma hierarquia de pontos de equilíbrio estável produzida por bifurcações, resultando em regime caótico. Os parâmetros demográficos obtidos por regressão exponencial foram também mudados para valores máximos e mínimos, a fim de analisar a influência deles sobre o comportamento dinâmico da espécie, tendo a razão sexual como variável independente. Bifurcações com janelas de periodicidade intercaladas com o regime caótico também foram encontradas.; Sex ratio is an essential component of life history to be considered in population growth. Chrysomya albiceps is a blowfly species with a naturally biased sex ratio. In this study...

Phenology, sex ratio, and spatial distribution among dioecious species of Trichilia (Meliaceae)

Morellato, LPC
Fonte: Georg Thieme Verlag Kg Publicador: Georg Thieme Verlag Kg
Tipo: Artigo de Revista Científica Formato: 491-497
ENG
Relevância na Pesquisa
66.17%
The flowering, sex ratio, and spatial distribution of four dioecious species of Trichilia (Meliaceae) were studied in a semi-deciduous forest in southeastern Brazil. All reproductive trees (T. clausseni, T. pallida and T. catigua) with dbh greater than or equal to5 cm within a 1-ha plot were collected, sexed, mapped and, for individuals of each species, the distances to the nearest neighbour of the same and opposite sex were measured. For the shrub species T elegans (dbh <5 cm), all reproductive individuals were sampled randomly in 10 samples of 10 x 10 m. The reproductive phenology was observed at weekly to monthly intervals from May 1988 to January 1990. The species are strictly dioecious, did not present any sex-mixed trees or sex switching during the study, and sex ratio did not differ significantly from 1:1. The size distributions and the relative size variation were not significantly different. between sexes. There was no significant segregation or clumping between individuals of either sex and no fruit production without pollination. Onset of flowering and flowering peak were synchronous between male and female plants for all species studied. Flower synchrony was related to outcrossing and pollinator attraction rather than climatic factors.

Sex ratio and morphological characteristics of rufous gnateaters, Conopophaga lineata (Aves, Passeriformes) in Atlantic forest fragments

Dantas, Gisele Pires de Mendonça; Santos, Fabrício Rodrigues dos; Marini, Miguel Ângelo
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.2%
Unequal sex ratios lead to the loss of genetic variability, decreasing the viability of populations in the long term. Anthropogenic activities often disturb the natural habitats and can cause alterations in sex ratio and morphological characteristics of several species. Forest fragmentation is a major conservation concern, so that understanding its effects in natural populations is essential. In this study, we evaluated the sex ratio and the morphological characteristics of Rufous Gnateaters (Conopophaga lineata (Wied, 1831)) in small and large forest fragments in Minas Gerais, Brazil. Birds (n = 89) were sexed by plumage characteristics and molecular markers. The molecular analysis showed that plumage is not a totally reliable method for sexing Rufous Gnateaters. We observed that sex ratio did not differ between large and small forest fragments, but birds in small fragments had larger wings and tarsus. Wing and tarsus changes may affect the movement ability of individuals within and among forest fragments. In conclusion, Rufous Gnateaters have been able to survive in both small and large Atlantic rain forest fragments without altering their sex ratio, but morphological changes can be prejudicial to their long term survival _______________________________________________________________________________ RESUMO; A razão sexual desigual pode levar à perda de variabilidade genética...

Sex ratio and morphological characteristics of rufous gnateaters, Conopophaga lineata (Aves, Passeriformes) in Atlantic forest fragments

Dantas,Gisele P. M.; Santos,Fabrício R.; Marini,Miguel Ângelo
Fonte: Fundação Zoobotânica do Rio Grande do Sul Publicador: Fundação Zoobotânica do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2009 EN
Relevância na Pesquisa
66.2%
Unequal sex ratios lead to the loss of genetic variability, decreasing the viability of populations in the long term. Anthropogenic activities often disturb the natural habitats and can cause alterations in sex ratio and morphological characteristics of several species. Forest fragmentation is a major conservation concern, so that understanding its effects in natural populations is essential. In this study, we evaluated the sex ratio and the morphological characteristics of Rufous Gnateaters (Conopophaga lineata (Wied, 1831)) in small and large forest fragments in Minas Gerais, Brazil. Birds (n = 89) were sexed by plumage characteristics and molecular markers. The molecular analysis showed that plumage is not a totally reliable method for sexing Rufous Gnateaters. We observed that sex ratio did not differ between large and small forest fragments, but birds in small fragments had larger wings and tarsus. Wing and tarsus changes may affect the movement ability of individuals within and among forest fragments. In conclusion, Rufous Gnateaters have been able to survive in both small and large Atlantic rain forest fragments without altering their sex ratio, but morphological changes can be prejudicial to their long term survival.

Effects of female diet and age on offspring sex ratio of the solitary parasitoid Pachycrepoideus vindemmiae (Rondani) (Hymenoptera, Pteromalidae)

Hu,Hao-Yuan; Chen,Zhong-Zheng; Duan,Bi-Sheng; Zheng,Jin-Tu; Zhang,Tong-Xin
Fonte: Sociedade Brasileira De Entomologia Publicador: Sociedade Brasileira De Entomologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
66.26%
Effects of female diet and age on offspring sex ratio of the solitary parasitoid Pachycrepoideus vindemmiae (Rondani) (Hymenoptera, Pteromalidae). Theories predict that females of parasitoid wasps would adjust the offspring sex ratio to environmental conditions in the oviposition patch, but the diet and age of females would also affect the sex ratio adjustment. Our focus was to test the effects of female diet and age on offspring sex ratio of the solitary parasitoid wasp, Pachycrepoideus vindemmiae (Rondani, 1875). Our results showed that females fed with honey had significantly less female biased offspring sex ratio than those fed only with water. Offspring sex ratio (male percentage) decreased with female age or female longevity at the beginning of oviposition but increased at the end. There should be a sperm limitation in P. vindemmiae females at the end of oviposition, and a higher frequency of unfertilized eggs were laid then. Females also laid more unfertilized eggs at the beginning of oviposition, which would be necessary to insure the mating among offspring. Male offspring developed faster and emerged earlier, which would also reduce the risk of virginity in offspring with female-biased sex ratio.

Florivory and sex ratio in Annona dioica St. Hil. (Annonaceae) in the Pantanal at Nhecolândia, southwestern Brazil

Paulino Neto,Hipólito Ferreira; Teixeira,Reinaldo Chaves
Fonte: Sociedade Botânica do Brasil Publicador: Sociedade Botânica do Brasil
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2006 EN
Relevância na Pesquisa
66.16%
Annona dioica St. Hil. is a species that grows to approximately 2 m tall and is very widespread in the cerrados. Individual plants of this androdioecious species produce numerous hermaphroditic or male flowers, but few fruits. The aim of this study was to determine the sex ratio among the plants and to compare the frequency of herbivory between male and hermaphroditic flowers. The fieldwork was done by studying flowering plants in grasslands used as pasture for cattle at Fazenda Nhumirim. One hundred and forty-seven male plants and 71 hermaphroditic plants were examined and produced a total of 194 and 94 flowers, respectively, during the study period. The male:hermaphrodite sex ratio was 2.07:1, and was similar to the male:hermaphrodite flower ratio of 2.06:1. The frequency of florivory rate in hermaphrodites was significantly higher than in male flowers (33.0%, n = 31, and 25.7%, n = 50, respectively; G = 14.83; d.f. = 1; p < 0.001). The mean fresh weights of male and hermaphroditic flowers were significantly different (8.38 ± 2.40 g vs. 6.93 ± 2.68 g, respectively; 0 ± SEM; n = 50 each; t = 2.479; d.f. = 49; p = 0.017). These results indicate that the low fruit set in this species can be explained by the sex ratio...

Sex ratio and dynamic behavior in populations of the exotic blowfly Chrysomya albiceps (Diptera, Calliphoridae)

Serra,H.; Godoy,WAC.; Von Zuben,FJ.; Von Zuben,CJ.; Reis,SF.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2007 EN
Relevância na Pesquisa
66.24%
Sex ratio is an essential component of life history to be considered in population growth. Chrysomya albiceps is a blowfly species with a naturally biased sex ratio. In this study, we evaluated the impact of changes in sex ratio on the dynamic behavior of C. albiceps using a density-dependent mathematical model that incorporated demographic parameters such as survival and fecundity. These parameters were obtained by exponential regression, with survival and fecundity being estimated experimentally as a function of larval density. Bifurcation diagram of the results indicated the evolution of stable equilibrium points as a function of sex ratio. A continually increasing sex ratio yielded a hierarchy of bifurcating stable equilibrium points that evolved into a chaotic regime. The demographic parameters obtained by exponential regression were also changed to maximum and minimum values in order to analyze their influence on dynamic behavior with sex ratio being considered as an independent variable. Bifurcations with periodicity windows between chaos regimes were also found.

Sex differences in brain plasticity: a new hypothesis for sex ratio bias in autism

Mottron, Laurent; Duret, Pauline; Mueller, Sophia; Moore, Robert D; Forgeot d’Arc, Baudouin; Jacquemont, Sebastien; Xiong, Lan
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
66.16%
Several observations support the hypothesis that differences in synaptic and regional cerebral plasticity between the sexes account for the high ratio of males to females in autism. First, males are more susceptible than females to perturbations in genes involved in synaptic plasticity. Second, sex-related differences in non-autistic brain structure and function are observed in highly variable regions, namely, the heteromodal associative cortices, and overlap with structural particularities and enhanced activity of perceptual associative regions in autistic individuals. Finally, functional cortical reallocations following brain lesions in non-autistic adults (for example, traumatic brain injury, multiple sclerosis) are sex-dependent. Interactions between genetic sex and hormones may therefore result in higher synaptic and consecutively regional plasticity in perceptual brain areas in males than in females. The onset of autism may largely involve mutations altering synaptic plasticity that create a plastic reaction affecting the most variable and sexually dimorphic brain regions. The sex ratio bias in autism may arise because males have a lower threshold than females for the development of this plastic reaction following a genetic or environmental event.

Generation of sex ratio biases in the red-tailed phascogale (Phascogale calura)

Foster, W.; Taggart, D.
Fonte: C S I R O Publishing Publicador: C S I R O Publishing
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
66.23%
Male semelparous dasyurid species are annual breeders that use a promiscuous mating system. These species have shown biases in litter sex ratios and, with females producing more young than they have available teats, this provides an opportunity for the manipulation of the sex ratio at birth. The sex ratio of embryos and pouch young, and the degree of embryonic overproduction, in red-tailed phascogales (Phascogale calura) was investigated to gain an understanding of the mechanism by which sex biases may be generated. The sex ratio of embryos did not differ from parity, but a male bias was observed in young attaching to teats. Females produced an average of 15.1 ± 1.9 corpora lutea and 10.5 ± 3.5 viable embryos, with no difference in fecundity observed with female age or weight. Because females only have eight teats, the overproduction of young, and male-biased attachment, was sufficient to explain the observed male bias in pouch young. No relationship was observed between maternal weight and sex ratio, but heavier females did tend to produce more ova. Meta-analysis of studies providing information on litter sex ratios in male semelparous dasyurid species did not show any consistent trend.; W.K. Foster and D.A. Taggart

The effect of glucosamine concentration on the development and sex ratio of bovine embryos

Kimura, K.; Iwata, H.; Thompson, J.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
66.26%
Glucosamine is a component of hyaluronic acid and an alternative substrate to glucose for the extracellular matrix synthesis of COCs. Its addition to an IVM medium reduces the glucose consumption of bovine COCs. Glucosamine is also metabolized to UDP-N-acetyl glucosamine (UDP-GlcNAc) via the hexosamine biosynthesis pathway and is utilized for O-linked glycosylation by the X-linked enzyme, O-linked GlcNAc transferase (OGT). Moreover, the inactivation of the second X chromosome in female embryos is influential in producing the sex ratio bias observed in vitro when embryos are cultured in the presence of glucose above 2.5mM. Accordingly, the aim of this study is to examine whether the presence of glucosamine during maturation or embryo culture causes a sex ratio bias in bovine blastocysts. Glucosamine was added to the medium in three different embryo developmental periods: in vitro maturation, the one-cell to eight-cell stage (before the maternal-zygotic transition, MZT), and the eight-cell to blastocyst stage (after MZT). When glucosamine was added during in vitro maturation, the developmental competence of oocytes was severely compromised. However, the sex ratio of embryos was not influenced. When glucosamine was added to embryo culture medium during development from one-cell to eight-cell stage (before MZT)...

Sex ratio theory applied to a macropod marsupial : Is reproduction by the Tammar Wallaby (Macropus eugenii) consistent with sex ratio theory?

Perryman, Aryn White
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
66.23%
Marsupial species provide an important research tool in attempts to unravel the complicated mechanisms of mammalian reproduction. Comparisons between metatherian and eutherian reproductive life history patterns used to achieve the same outcomes, illuminates processes that have been difficult to investigate in eutherian species alone. Adaptive sex allocation is one such area that has provided equivocal data that is much scrutinized and debated amongst scientists. The theory that has provided the most disparity in the literature, and lead to the most debate, is the Trivers-Willard Model (TWM) (Trivers & Willard, 1973). The TWM proposes that, in polygynous mammalian species where the male has increased variability in reproductive returns, mothers in ‘good condition’ should bias their offspring towards sons, to maximise their fitness. There are three main assumptions associated with the theory: 1) that sons will benefit more than daughters from increased maternal resource allocation, 2) that juvenile condition predicts adult condition and 3) that maternal quality is a predictor of offspring quality. Much of the previous support for the TWM has been based on research in eutherian species (e.g. ungulate species), which usually tests only one assumption at a time by a posteriori application of the theory to observed data. Macropod species fill similar niches to ungulate species in other ecosystems and provide easy access to pouch young at a very early stage of development...

Natal-host environmental effects on juvenile size, transmission success, and operational sex ratio in the entomopathogenic nematode Steinernema carpocapsae

Therese, M.O.; Bashey, F.
Fonte: American Society of Parasitologists Publicador: American Society of Parasitologists
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
66.21%
Trans-host effects can alter the ecological and evolutionary dynamics of parasite and host populations. Here, we examine whether resource limitation within a parasite's natal host affects propagule size and influences parasite fitness in a new host. To alter resource competition, we infected caterpillars with 3 doses of the nematode Steinernema carpocapsae and harvested transmission-stage juveniles either early or late in the infection. We measured the size of these juveniles, and then we examined their ability to colonize and their sex ratio upon maturity in a new host. We found a trade-off between the cumulative number and size of nematodes emerging from a host. Emerging nematode size declined significantly over the time course of the infection, but dose had no significant effects. Larger, early emerging nematodes had greater success in colonizing a new host than smaller, later emerging nematodes, independently of whether they needed to locate the host. Furthermore, although early emerging nematodes resulted in an equal sex ratio in the new host, late emerging nematodes resulted in female-biased populations. These transmission and sex-ratio effects demonstrate that conditions in the natal host can affect parasite fitness, and they suggest that trans-host effects need to be more fully integrated into our studies of parasite populations.

Female Fertilization: Effects of Sex-Specific Density and Sex Ratio Determined Experimentally for Colorado Potato Beetles and Drosophila Fruit Flies

Vahl, Wouter K.; Boiteau, Gilles; de Heij, Maaike E.; MacKinley, Pamela D.; Kokko, Hanna
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.16%
If males and females affect reproduction differentially, understanding and predicting sexual reproduction requires specification of response surfaces, that is, two-dimensional functions that relate reproduction to the (numeric) densities of both sexes. Aiming at rigorous measurement of female per capita fertilization response surfaces, we conducted a multifactorial experiment and reanalyzed an extensive data set. In our experiment, we varied the density of male and female Leptinotarsa decemlineata (Colorado potato beetles) by placing different numbers of the two sexes on enclosed Solanum tuberosum (potato plants) to determine the proportion of females fertilized after 3 or 22 hours. In the reanalysis, we investigated how the short-term fertilization probability of three Drosophila strains (melanogaster ebony, m. sepia, and simulans) depended on adult sex ratio (proportion of males) and total density. The fertilization probability of female Leptinotarsa decemlineata increased logistically with male density, but not with female density. These effects were robust to trial duration. The fertilization probability of female Drosophila increased logistically with both sex ratio and total density. Treatment effects interacted in m. sepia, and simulans. These findings highlight the importance of well-designed...

Sex ratio in two species of Pegoscapus wasps (Hymenoptera: Agaonidae) that develop in figs: can wasps do mathematics, or play sex ratio games?

Ramírez-Benavides,William; Monge-Nájera,Julián; Chavarría,Juan B
Fonte: Revista de Biología Tropical Publicador: Revista de Biología Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2009 EN
Relevância na Pesquisa
66.22%
The fig pollinating wasps (Hymenoptera: Agaonidae) have obligate arrhenotoky and a breeding structure that fits local mate competition (LMC). It has been traditionally assumed that LMC organisms adjust the sex ratio by laying a greater proportion of male eggs when there is superparasitism (several foundresses in a host). We tested the assumption with two wasp species, Pegoscapus silvestrii, pollinator of Ficus pertusa and Pegoscapus tonduzi, pollinator of Ficus eximia (= F. citrifolia), in the Central Valley of Costa Rica. Total number of wasps and seeds were recorded in individual isolated naturally colonized syconia. There was a constant additive effect between the number of foundresses and the number of males produced in the brood of a syconium, while the number of females decreased. Both wasp species seem to have precise sex ratios and probably lay the male eggs first in the sequence, independently of superparasitism and clutch size: consequently, they have a non-random sex allocation. Each syconium of Ficus pertusa and of F. eximia colonized by one foundress had similar mean numbers of females, males, and seeds. The two species of wasps studied do not seem to adjust the sex ratio when there is superparasitism. Pollinating fig wasp behavior is better explained by those models not assuming that females do mathematical calculations according to other females’ sex ratios...

Sex ratio and breeding of white-lipped peccaries Tayassu pecari (Artiodactyla: Tayassuidae) in a Costa Rican rain forest

Altrichter,Mariana; Drews,Carlos; Carrillo,Eduardo; Sáenz,Joel
Fonte: Revista de Biología Tropical Publicador: Revista de Biología Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2001 EN
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White-lipped peccaries are non-seasonal breeders in South America, but little is known about their reproduction in Central America. There are few studies about the sex ratio of this species in the field. We studied the reproduction and sex ratio of white-lipped peccaries during 200 hours of field observation of four radiomarked and two unmarked herds, from July 1996 to April 1997, in Corcovado National Park, Costa Rica. Sex ratio data of three additional, radiomarked herds observed in 1998 were also included. We recorded numbers of mountings, presence of newborns and numbers of nursing interactions. The peccaries showed a distinct reproductive seasonality, with one mating peak in February and another in July. The greatest number of newborns and the peak in nursing activity were observed during July and August, when fruit availability for the peccaries was high. The adult sex ratio was significantly female biased (1.4:1 - 1.8:1), also in contrast with South American populations.