248 resultados para FEMALE-BIASED SEX RATIO


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Here we study 13 families with stuttering. of the 13 families, 9 were persistent stutterers and 4 were recovered stutterers. In the 9 families with persistent stuttering, 24 were male and 10 were females. of the 4 families with recovered stutterers, 17 were male and 3 were female. of the 17 males, 12 were persistent stutterers and 5 recovered after adolescence. All females were recovered stutterers. We conclude with a short discussion of recent molecular Studies. (c) 2006 Wiley-Liss, Inc.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The mottled shore crab P. transversus is probably the most common brachyuran crab living in the marine rocky intertidal of southeastern Brazil. However, its biology is largely unknown. In this study, some aspects of the population biology of this species are investigated. Distribution of individuals in the intertidal range is heterogeneous. Sabellariid worm reefs and mytilid mussel beds can be considered as nursery grounds retaining most part of juveniles, while the rocky surface is mostly inhabited by adults, which find safety shelters in rock crevices. Annual size frequency distributions revealed clues of population stability and indicated that young individuals reach the adult habitat in a gradual process. Sex-ratio follows the 1:1 proportion in smaller size classes but is biased towards males in larger ones. Higher mortality in larger females is indicated as a possible cause of this pattern. Ovigerous ratio shows a remarkable seasonality in which highest percentages of ovigerous females occur during summer months, while recruitment of young is more intense from April to July, suggesting a very extensive larval development. Once established in the intertidal zone, young recruits will develop to mature individuals in late spring, when molting crabs become scarce and proportion of breeding females increases. Therefore, growth and reproduction are in a great part temporally separated, allowing an annual life cycle in which settlement, growth and breeding may take place within a I-yr period.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fêmeas de Cotesia flavipes (Cam.) foram introduzidas, individualmente, em placas de Petri contendo uma larva de seu hospedeiro Diatraea saccharalis (Fabr.). Permitiu-se que cada fêmea de C. flavipes realizasse posturas uma ou duas vezes em uma mesma larva. O período de emergência das larvas e dos adultos, a razão sexual, o número de larvas e pupas inviáveis e a longevidade dos adultos de C. flavipes registrados nas duas condições experimentais (uma ou duas posturas) foram comparados. Os resultados revelaram que duas oviposições sucessivas no hospedeiro não alteraram a razão sexual na descendência, mas aumentaram o número de parasitóides e também o número de larvas e pupas inviáveis.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Espécimes de Rioraja agassizi foram mensalmente coletados em águas ao largo de Santos, sudeste do Brasil entre as latitudes 23º37'S e 27º40'S, desde março de 2005 até março de 2006. Um total de 278 machos e 1023 fêmeas foi capturado. A amplitude de profundidade de ocorrência foi 10-120 m, estando a espécie ausente em profundidades >120 m. A razão sexual favoreceu as fêmeas. A amplitude completa de comprimentos de R. agassizi esteve representada e oscilou nas fêmeas entre 16.0-59.4 cm comprimento e nos machos entre 13.0-47.2 cm. O tamanho médio das fêmeas foi significativamente maior do que dos machos. A distribuição de freqüência de comprimentos por amostras agrupadas foi assimétrica em ambos os sexos. As curvas da relação comprimento-largura foram sexualmente dimórficas. As fêmeas foram mais largas que os machos em todas as classes de comprimento maiores do que 25 cm. As curvas comprimento-peso total foram significativamente diferentes das curvas comprimento-peso eviscerado em ambos os sexos. As fêmeas foram mais pesadas do que os machos para uma determinada classe de comprimento. O coeficiente angular b foi <3 nos machos (alometría negativa) e nas fêmeas, mas com exceção da primavera, onde a alometría foi positiva (b>3). O fator de condição variou significativamente ao longo do ano em ambos os sexos.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Observations of the developmental biology of Loxosceles gaucho Gertsch, 1967, the brown spider of southeastern Brazil are scarce. The present study reports the method of individualized rearing of 18 populations of L. gaucho, kept in laboratory under varied diet conditions, and characterizes their nympho-imaginal period as well as factors related to their reproduction. Females built the first egg sac about 20 days after copulation and nymphs hatched 40 days after the laying date. Average offspring was 61.3 spiderlings and females usually built three to four successive egg sacs in a period of five to seven months. First nymphs initiated their predatory activity between the 5th and 8th days after hatching and the majority reached adulthood within six moults (range of five to eight) in approximately 15 to 17 months (male) and 15.5 to 18 months (female). The average sex ratio equaled 1.0:1.7 (male:female). The wide individual variability of this species intermoult intervals is herewith expressed by the intermoult rate, which was fairly uniform for both intra and interpopulations and gives a relevant aspect for a general idea of the life cycles of spiders.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Although the Brazilian sharpnose shark, Rhizoprionodon lalandii (Muller and Henle, 1839), is an inshore species widely distributed in the Western Atlantic from Panama to Uruguay, there is little available information on its biology. During a long-term study of small coastal sharks caught by gill net fisheries in southeastern Brazil (PROJETO CACAO), 3643 specimens of R. lalandii were examined, comprising 61.3% of the total sharks,and including all sizes classes, from 30 to 78,5 cm TL., and weights from 100 to 2950 g. The length-weight relationships were not significantly different between sexes, Overall sex ratio favoured the males slightly at the rate of 1.3: 1. Sex ratios, however, did differ significantly between season and size classes. This species occurred in this area all year long. Three seasonal size-class Occurrence patterns were recognized: (1) between October and March, the juveniles were more frequents (2) from April to July, adults were most common, and (3) from August to September, neonates were most numerically abundant. Such patterns we to associated with reproductive tactics that may reduce intra-specific and inter-specific competition with hammerhead shark neonates (Sphyrna lewini). probably result in reduced natural mortality of the offspring during their first few months. (C) 2005 Elsevier B.V. All rights reserved.

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We report biological data of two generations of Amblyomma triste in laboratory and compared the suitability of different host species. Infestations by larval and nymphal stages were performed on guinea pigs (Cavia porcellus), chickens (Gallus gallus), rats (Rattus norvegicus), rabbits (Oryctolagus cuniculus), wild mice (Calomys callosus), dogs (Canis familiaris) and capybaras (Hydrochaeris hydrochaeris). Infestations by adult ticks were performed on dogs, capybaras and rabbits. Tick developmental periods were observed in an incubator at 27degreesC and RH 90%. Guinea pigs were the most suitable hosts for larvae and nymphs, followed by chickens. The remaining host species were less suitable for immature ticks as fewer engorged ticks were recovered from them. Mean larval feeding periods varied from 3.8 to 4.7 d between different host species. Mean larval premolt periods ranged from 8.9 to 10.4 d. Nymphal mean feeding periods varied from 4.2 to 6.2 d for ticks fed on different host species. Premolt period of male nymphs (mean: 15.4 d) was significantly longer than that of female nymphs (14.7 d). Female nymphs were significantly heavier than male nymphs. The overall sex ratio of the adult ticks emerged from nymphs was 0.9:1 (M:F). Capybaras were the most suitable host for the tick adult stage as significantly more engorged females were recovered from them and these females were significantly heavier than those recovered from dogs or rabbits. The life cycle of A. triste in laboratory could be completed in an average period of 155 d. The potential role of guinea pigs, birds and capybaras, as hosts for A. triste in nature, is discussed.