oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 80 )

2018 ( 314 )

2017 ( 302 )

2016 ( 358 )

Custom range...

Search Results: 1 - 10 of 9091 matches for " sexual ratio "
All listed articles are free for downloading (OA Articles)
Page 1 /9091
Display every page Item
Estimativas de parametros populacionais e demográficos de Ozotoceros bezoarticus (Artiodactyla, Cervidae) em Piraí do Sul, Paraná, sul do Brasil
Braga, Fernanda G.;Kuniyoshi, Yoshiko S.;
Iheringia. Série Zoologia , 2010, DOI: 10.1590/S0073-47212010000200003
Abstract: this study was conducted in two private properties in the municipality of piraí do sul (paraná state, southern brazil). sixteen monthly visits were made each one lasting three days between february 2001 and may 2002. the study aimed at the observation of pampas deer biology (ozotoceros bezoarticus linnaeus, 1758), and the evaluation of main impacts to this population. we computed 1,065 observations of estimated 71.45 individuals. the average size of the groups was 2.29 (sd ± 0.55) animals, and the sexual ratio was 0.83. isolated deer accounted for 40% of the observations, whereas the largest group comprised 10 individuals. it was recorded a peack period of births between september and november, although births were observed along all the studied period. thirty-four deaths were recorded corresponding to a 47.6% death rate. the main causes of death were predatory actions by cougar puma concolor (linnaeus, 1771), hunting and individuals being run over by motor vehicles. the studied population is seriously endangered and it will not escape extinction unless certain policies to guarantee its conservation are adopted. these policies should include correct management of the areas and control of pressure vectors.
Dimorfismo sexual en la proporción entre el segundo y cuarto digito (2D/4D) de Gonatodes albogularis (Gekkonidae) en Colombia
Pe?uela, Mauricio;
Papéis Avulsos de Zoologia (S?o Paulo) , 2011, DOI: 10.1590/S0031-10492011001600001
Abstract: the second-to-fourth digit ratio (2d/4d) is a well-studied sexual dimorphism that likely arises as a result of prenatal androgenic effects on homeobox gene expression. this dimorphism has been found to exhibit interesting phylogenetic patterns in which females have larger ratios than males among most mammalian species and males have larger ratios than females in most avian and reptilian species. this study measured the second and fourth digits of all limbs from 25 adult males and 25 adult females of gonatodes albogularis. there were no significant differences between the (2d/4d) for gender as sexual dimorphism of the species. these results indicate that this species of tree lizard deviates from the ratio shown by diapsid species. possible associated environmental factors are discussed.
Biologia da tra?a das crucíferas, Plutella xylostella Linnaeus (Lepidoptera, Yponomeutidae), sob condi??es controladas de temperatura, e parasitóides associados: Part III. Estudo sobre a biologia de Apanteles piceotrichosus (Blanchard) (Hymenoptera, Braconidae): análise do efeito de endocruzamento
Gon?alves, Rafaelle R.;Mare, Rocco A. Di;
Revista Brasileira de Zoologia , 2005, DOI: 10.1590/S0101-81752005000300045
Abstract: the inbreeding in natural populations results in a loss in the genetic variability that can influence juvenile and adult mortality, the size, viability and fertility of the offspring, as well as the individuals morphology. apanteles piceotrichosus (blanchard, 1943) (hymenoptera, braconidae) is a plutella xylostella linnaeus,1758 parasitoid (lepidoptera, yponomeutidae) that has been attracting a lot of attention to a biocontrol purpose, because it can be used as agent of biological control. for the creation and liberation of parasitoids are necessary studies on its biology. the objective of the present study was carried out to examine the inbreeding effect on the mortality, longevity and sexual ratio of a. piceotrichosus. the parasitoid attack rate was also observed. the crossings, scheduled, were made starting from individuals collected in field and breed in laboratory under controlled conditions. were not observed significant differences in mortality and longevity of a. piceotrichosus, as well as in the rate of attack of the parasitoid on the host. the sexual ratio showed significant differences among the control and inbreeding group. even so differences were not observed inside of the inbreeding group.
Moscas ectoparasitas (Diptera, Streblidae) de morcegos (Chiroptera, Phyllostomidae) no sul do Brasil: associa??es hospedeiros-parasitos e taxas de infesta??o
Rui, Ana M.;Graciolli, Gustavo;
Revista Brasileira de Zoologia , 2005, DOI: 10.1590/S0101-81752005000200021
Abstract: hosts-parasites associations, including infestation rates, between ectoparasitic bat flies of the family streblidae and bats of the family phyllostomidae were studied in atlantic forest habitats in southern brazil. for the more abundant phyllostomid bats, the prevalence and mean intensity of fly infestation were determined during the different seasons of the year and in relation to the sex and age of their hosts. from four species of bats (anoura caudifera (e. geoffroy, 1818), artibeus fimbriatus gray, 1838, artibeus lituratus (olfers, 1818) and sturnira lilium e. geoffroy, 1810), were collected 118 specimens of bat flies belonging to seven species (anastrebla caudiferae wenzel, 1976, megistopoda aranea (coquillett, 1899), megistopoda proxima (séguy, 1926), metelasmus pseudopterus coquillett, 1907, paratrichobius longicrus (miranda ribeiro, 1907), trichobius phyllostomae kessel, 1925 and trichobius tiptoni wenzel, 1976). low infestation rates were found in a. lituratus, a. fimbriatus and s. lilium and there were a tendency for the bats to be more parasited in summer and autumn, probably related to the seasonal temperatures in the region studied because such temperatures affect the reproductive and mortality rates of the ectoparasites. for a. lituratus, the age or sex of the host did not affect the infestation rates by p. longicrus. although the age or sex of s. lilium did not, in general, affect the rate of infestation by m. proxima, juvenile s. lilium appeared to be more frequently parasitized by m. proxima than did adult bats. the data indicate that there are no behavioral differences linked to the age and sex of the species of phyllostomid bats studied which favor or disfavor infestation by streblidae.
Sexual dimorphism in shells of Cochlostoma septemspirale (Caenogastropoda, Cyclophoroidea, Diplommatinidae, Cochlostomatinae)
Fabian Reichenbach,Hannes Baur,Eike Neubert
ZooKeys , 2012, DOI: 10.3897/zookeys.208.2869
Abstract: Sexual dimorphisms in shell-bearing snails expressed by characteristic traits of their respective shells would offer the possibility for a lot of studies about gender distribution in populations, species, etc. In this study, the seven main shell characters of the snail Cochlostoma septemspirale were measured in both sexes: (1) height and (2) width of the shell, (3) height and (4) width of the aperture, (5) width of the last whorl, (6) rib density on the last whorl, and (7) intensity of the reddish or brown pigments forming three bands over the shell. The variation of size and shape was explored with statistical methods adapted to principal components analysis (PCA) and linear discriminant analysis (LDA). In particular, we applied some multivariate morphometric tools for the analysis of ratios that have been developed only recently, that is, the PCA ratio spectrum, allometry ratio spectrum, and LDA ratio extractor. The overall separation of the two sexes was tested with LDA cross validation.The results show that there is a sexual dimorphism in the size and shape of shells. Females are more slender than males and are characterised by larger size, a slightly reduced aperture height but larger shell height and whorl width. Therefore they have a considerable larger shell volume (about one fifth) in the part above the aperture. Furthermore, the last whorl of females is slightly less strongly pigmented and mean rib density slightly higher. All characters overlap quite considerably between sexes. However, by using cross validation based on the 5 continuous shell characters more than 90% of the shells can be correctly assigned to each sex.
Morfometria e mortalidade em pupas e adultos de Brassolis astyra (Nymphalidae, Morphinae)
Salgado-Neto, Geraldo;Di Mare, Rocco Alfredo;
Iheringia. Série Zoologia , 2009, DOI: 10.1590/S0073-47212009000200012
Abstract: the data presented are based on brassolis astyra godart, 1824 individuals sampled randomly in four locations of the state of rio grande do sul, brazil: tupanciret?, s?o martinho da serra, santa maria - two places. except in s?o martinho da serra, the data were obtained in urban areas, on syagrus romanzoffianum palms (palmaceae). the following parameters were investigated: egg laying number, hatching eggs index, number of miscarried eggs, eggs positioning on the host plant, sex ratio, parasitoid index, emergency pupa-adult frequency, longevity of pupae and adult stages, mass and volume of the pupae and morphometric measurements of pupae and adults' wings. of eggs collected in tupanciret?, 46% hatched, 43% had been parasitized and 11% were miscarried. on the other hand, in s?o martinho da serra only 4% of the eggs collected hatched, 95% had been parasitized and 1% were miscarried. in the other localities no eggs were found. based on adults emerged from the pupae, it was verified that 77% of the males and females presented a normal morphology (viable) and 23% were malformed. the differences in the average values estimated for pupal longevity among the study sites, were statistically significant. the average frequency of adults was 0.47. the data obtained showed a sexual dimorphism in size (weigh) and form (volume) of the pupae. this suggests that the size and the form of the pupae can determine the adults' viability. such effect could be associated with a stabilizing selection, where would be associated to optima values average of weigh and form. although the origin of the sampled individuals varied, the parameters that determine the size and shape are in the same direction when comparing the two sexes. data on longevity and mortality suggest that the estimated values can be influenced by the variability and ecology of the population from which the larvae were sampled.
Variabilidade genética e limite da sele??o em popula??es de diferentes tipos de acasalamento
Cunha, E.E.;Euclydes, R.F.;Torres, R.A.;Lopes, P.S.;Ribeiro Júnior, J.I.;Carneiro, P.C.S.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2004, DOI: 10.1590/S0102-09352004000200015
Abstract: populations of five different mating designs, submitted to selection based on best linear unbiased predicto (blup)r, were evaluated regarding to genetic losses by fixation of unfavorable alleles and selection limit, during 50 generations. simulated data were used to obtain the genome of all individuals of the populations. a quantitative trait with heritability of 0.10 was studied in the selected populations, with the following structure: sexual ratio of 10, 20, 25, and 50 and effective population size of 36.36, 19.05, 15.38 and 7.84, respectively. for each sexual ratio different populations were generated corresponding to the following mating designs: preferential matings between half and full sibs, preferential matings between half sibs, random matings, exclusion of matings between full sibs and exclusion of matings of half and full sibs. smallest percentage of unfavorably fixed loci and the highest selection limit were observed in the lower sexual ratio (d= 10). better differentiation between the studied mating designs was also observed for the lower sexual ratio.
Distribución y estructura poblacional del cangrejo Halicarcinus planatus (Brachyura, Hymenosomatidae) en el Canal Beagle, Tierra del Fuego
Diez,Mariano J; Florentín,Olga; Lovrich,Gustavo A;
Revista de biología marina y oceanografía , 2011, DOI: 10.4067/S0718-19572011000200005
Abstract: the crab halicarcinus planatus is the only hymenosomatid that inhabits the southern tip of south america and has a sub-antarctic distribution, including the peri-antarctic islands and new zealand. in this paper, we report the abundance and population structure of h. planatus for a year in the intertidal zone of bahía brown, beagle channel, tierra del fuego. moreover, we show variations in the population structure in other beaches and environments of the channel. in contrast with males, female density showed monthly variations and was higher during austral summer months. high densities of h. planatus could be related with low mortality during the larval stage and oceanographic features of bahía brown, probably enhanced by the presence of both culture and mussel beds, substrates where settlement would occur. the populational sex ratio was biased towards females only in summer, while the operational sex ratio was biased towards males during all periods studied, suggesting strong competition among males for mating. in turn, males were present only in the intertidal zone of bahía brown and macrocystis pyrifera but were absent in the other studied intertidal areas.this is perhaps related to the lack of shelter in the subtidal zone of bahía brown. recruitment occurs in two different periods, summer (january-february) and autumn-winter (may-june), which corresponds with the two larval cohorts of h. planatus in the beagle channel.
Sex-dependent foraging effort and vigilance in coal-crested finches, Charitospiza eucosma (Aves: Emberizidae) during the breeding season: evidence of female-biased predation?
Diniz, Pedro;
Zoologia (Curitiba) , 2011, DOI: 10.1590/S1984-46702011000200003
Abstract: sexual dimorphism in birds is often attributed to sexual selection, but another interpretation suggests the evolution of this phenomenon by natural selection. predation may be an important selective pressure, acting mainly on females. in this study, i tested the latter hypothesis on the coal-crested finch (charitospiza eucosma oberholser, 1905) in a neotropical savanna of the central brazil (cerrado). i used capture methods for ascertaining the sex ratio in the population, and focal observations to gather behavioral data. my results show that the sex ratio is skewed toward males (1:1.39). males were more vigilant, vocalized for longer periods of time, and used higher perches than females. females foraged more, spent more time on parental care and remained on the ground for longer periods than males. these results support the 'foraging effort hypothesis, suggesting that females are more preyed upon because they spend more time foraging. ultimately, this may reflect the fact that females invest more on parental care than males. the sex-dependent parental investment may favor the evolution of different antipredator strategies in males and females: the camouflage in females as a less efficient strategy than vigilance in males.
Aspectos reproductivos de una población del charal Menidia jordani (Woolman) del Lago de Metztitlán, Hidalgo
Ibá?ez, Ana Laura;García Calderón, José Luis;Torres-Orozco B., Roberto;
Hidrobiológica , 2008,
Abstract: menidia jordani is a silverside species naturally distributed in the mexican and lerma drainage areas and has in metztitlán lake it most eastern area of distribution in a lentic system. the analysis of the reproductive biology of this species showed that even metztitlán lake is the extreme frontier of their distribution conserved its reproduction phenology in relation with other populations. the highest standard length was 58 mm and the length at first sexual maturation was at 43 mm. sexual ratio inequality was manifested in mayor proportion of females during all collects with exception of january of 2004.
Page 1 /9091
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.