973 resultados para Sexual-dimorphism


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

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Pós-graduação em Ciências Biológicas (Zoologia) - IBB

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

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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ln order to predict the facial growth using Jarahak's analysis, cephalometric radiographies of 120 subjects during the mixed dentition and between 6 and 10 years of age were studied. From the total, 60 subjects (30 males and 30 females) were classified as Angle's Class I and 60 subjects (30 males and 30 females) were classified as Angle's Class II, Division 1. AIl subjects did not receive any orthodontic treatment. The proportion between anterior and posterior facial heigth (SGo-NMe) was studied, which is determined by the formula PFH x 100/ AFH = %, neither being straight (> 62% < 65), clockwise ( > 58% < 62%) and anti-clockwise ( > 65% - 80%). Mean average, standard deviation and facial height proportion (SGo - NMe) were determined for males and females according to Angle's classification of malocc!usion. Sexual dimorphism was examined with regard to different types of Angle's malocclusion and the direction of the facial growth, and the correlation of four cephalometrics measurements were analvsed

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Heterochrony, the change in timing of developmental processes, is thought to be a key process shaping the numerous limb morphologies of tetrapods. Through a delayed offset in digit development, all cetaceans (i.e., whales, dolphins, and porpoises) have evolved supernumary phalanges (hyperphalangy). Moreover, some toothed cetaceans further alter digital morphologies by delayed endochondral and perichondral ossification of individual elements. In the harbor porpoise (Phocoena phocoena), these paedomorphic patterns have created poorly ossified phalangeal elements. However, no studies have addressed this morphology in other porpoise taxa. This study documents the timing of carpal and digital epiphyseal ossification in the poorly studied vaquita (Phocoena sinus) based on radiographs (n = 18) of known-age specimens. Patterns of vaquita manus ossification were compared between other porpoise and delphinid taxa. Adult vaquitas are paedomorphic in carpal, metacarpal, and digital development as they maintain a juvenile ossification pattern relative to that of other porpoise species of equivalent ages. Vaquitas also ossify fewer carpal elements as compared to other porpoise and some delphinid cetaceans, and ossification arrests relative to that of the harbor porpoise. Vaquitas also display sexual dimorphism as females reach a greater body size and display more ossified elements in the manus relative to their paedomorphic male cohorts.

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Fifty-one slimy sea plumes (Pseudopterogorgia americana Gmelin, 1791) were sampled for caridean shrimps at Guana Island, British Virgin Islands, during one week in July 1992. Sam- pling depth ranged from 3-22 m. Nine species were collected: Hippolyte nicholsoni Chace, 1972; Latreutes sp.; Neopontonides chacei Heard, 1986; Perclimenes cf. patae Heard and Spotte, 1991; Periclimenes cf. pauper Holthuis, 1951; Periclimenes sp.; Pseudocoutierea antillensis Chace, 1972; Tozeuma cf. cornutum Milne Edwards, 1881; and Trachycaris rugosa (Bate, 1888). A total of 1,418 specimens (including fragments) was obtained. The number of shrimp species per gorgonian ranged from 1-5; one gorgonian harbored 156 shrimps. The two predominant species, N. chacei and H. nicholsoni, occupy different mean depths (12.6 and 8.2 m, respectively). Sexual dimorphism assessed with Mann-Whitney U-tests was not apparent in the specimens of N. chacei (P > 0.05), but females of H. nicholsoni were significantly larger than males (P < 0.001). Minimum carapace length (CL, the tip of the rostrum to the posterior dorsal margin of the carapace) at which male N. chacei acquire a single appendix masculina spine is 1.25 mm; male H. nicholsoni can acquire a single spine at 0.9 mm CL. Histological sections of male N. chacei showed that shrimp with 0 or 1 spine are least likely to be mature. Female N. chacei can become ovigerous at 1.9 mm CL and female H. nicholsoni at 1.2 mm CL. The taxonomic status of 5 of the 9 species collected is uncertain.

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Moose Alces alces gigas in Alaska, USA, exhibit extreme sexual dimorphism, with adult males possessing large, elaborate antlers. Antler size and conformation are influenced by age, nutrition and genetics, and these bony structures serve to establish social rank and affect mating success. Population density, combined with anthropogenic effects such as harvest, is thought to influence antler size. Antler size increased as densities of moose decreased, ostensibly a density-dependent response related to enhanced nutrition at low densities. The vegetation type where moose were harvested also affected antler size, with the largest-antlered males occupying more open habitats. Hunts with guides occurred in areas with low moose density, minimized hunter interference and increased rates of success. Such hunts harvested moose with larger antler spreads than did non-guided hunts. Knowledge and abilities allowed guides to satisfy demands of trophy hunters, who are an integral part of the Alaskan economy. Heavy harvest by humans was also associated with decreased antler size of moose, probably via a downward shift in the age structure of the population resulting in younger males with smaller antlers. Nevertheless, density-dependence was more influential than effects of harvest on age structure in determining antler size of male moose. Indeed, antlers are likely under strong sexual selection, but we demonstrate that resource availability influenced the distribution of these sexually selected characters across the landscape. We argue that understanding population density in relation to carrying capacity (K) and the age structure of males is necessary to interpret potential consequences of harvest on the genetics of moose and other large herbivores. Our results provide researchers and managers with a better understanding of variables that affect the physical condition, antler size, and perhaps the genetic composition of populations, which may be useful in managing and modeling moose populations.

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The relative growth and population structure of the terebellid Nicolea uspiana were investigated in the intertidal zone of a rocky shore on the south-east coast of Brazil, from May 2006 to May 2007. Eight hundred and forty-seven individuals of N. uspiana were analysed: 391 males, 163 females, and 293 immatures. Although significant differences in some morphometric parameters were found, there was no sexual dimorphism between males and females. There were differences in total length, width of segments, and length of the notopodial region between matures and immatures. The negative allometry of the total length in relation to five other parameters showed that this feature is a good measure for estimating the individual size, which was then used in the analysis of population structure. This population of N. uspiana showed a bimodal size frequency distribution, with immature and mature individuals found during the entire year. This pattern indicates continuous reproduction, with each cohort growing for at least three to four months and being responsible for two consecutive settlement peaks.

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Chimpanzees have been the traditional referential models for investigating human evolution and stone tool use by hominins. We enlarge this comparative scenario by describing normative use of hammer stones and anvils in two wild groups of bearded capuchin monkeys (Cebus libidinosus) over one year. We found that most of the individuals habitually use stones and anvils to crack nuts and other encased food items. Further, we found that in adults (1) males use stone tools more frequently than females, (2) males crack high resistance nuts more frequently than females, (3) efficiency at opening a food by percussive tool use varies according to the resistance of the encased food, (4) heavier individuals are more efficient at cracking high resistant nuts than smaller individuals, and (5) to crack open encased foods, both sexes select hammer stones on the basis of material and weight. These findings confirm and extend previous experimental evidence concerning tool selectivity in wild capuchin monkeys (Visalberghi et al., 2009b; Fragaszy et al., 2010b). Male capuchins use tools more frequently than females and body mass is the best predictor of efficiency, but the sexes do not differ in terms of efficiency. We argue that the contrasting pattern of sex differences in capuchins compared with chimpanzees, in which females use tools more frequently and more skillfully than males, may have arisen from the degree of sexual dimorphism in body size of the two species, which is larger in capuchins than in chimpanzees. Our findings show the importance of taking sex and body mass into account as separate variables to assess their role in tool use. (C) 2011 Elsevier Ltd. All rights reserved.