Efeito da somatotropina na hipertrofia das fibras musculares esqueléticas e precocidade reprodutiva de novilhas Nelore

O trabalho objetivou avaliar o desempenho produtivo, precocidade sexual e hipertrofia das fibras musculares esqueléticas em resposta à aplicação de somatotropina bovina recombinante (rbST). Foram utilizadas 58 novilhas Nelore de sete meses de idade com peso vivo médio de 193 kg. O delineamento experimental foi inteiramente casualizado, em um esquema fatorial incompleto e dividido em duas fases experimentais. Na primeira fase, com duração de 150 dias, os animais foram divididos em dois grupos, de acordo com os níveis de rbST, 0 mg (controle) e 500 mg, a cada 28 dias. Na Fase II, os animais do grupo controle da Fase I foram divididos em 15 e 14 novilhas, que receberam 0 mg e 500 mg de rbST, respectivamente; os animais tratados com 500 mg na Fase I foram divididos em 15 e 14 novilhas e receberam 500 mg e 1.000 mg de rbST, respectivamente, com intervalos de 28 dias, e dieta em regime de pastejo, durante 180 dias. Foram retirados fragmentos do músculo semitendinosus para análise das fibras, no início e final da Fase I. Os animais foram pesados a cada 28 dias. Os resultados mostraram que não houve diferença significativa (p>0,05) entre os tratamentos quanto ao ganho de peso e quanto à precocidade sexual. Quanto ao diâmetro das fibras, os animais que receberam rbST tiveram um aumento significativo (p<0,01) tanto nas fibras de contração lenta quanto nas fibras de contração rápida em relação aos animais-controle.

Cryptic speciation and recombination in the fungus Paracoccidioides brasiliensis as revealed by gene genealogies

Paracoccidioides brasiliensis is the etiologic agent of paracoccidioidomycosis, a disease confined to Latin America and of marked importance in the endemic areas due to its frequency and severity. This species is considered to be clonal according to mycological criteria and has been shown to vary in virulence. To characterize natural genetic variation and reproductive mode in this fungus, we analyzed P. brasiliensis phylogenetically in search of cryptic species and possible recombination using concordance and nondiscordance of gene genealogies with respect to phylogenies of eight regions in five nuclear loci. Our data indicate that this fungus consists of at least three distinct, previously unrecognized species: S1 (species 1 with 38 isolates), PS2 (phylogenetic species 2 with six isolates), and PS3 (phylogenetic species 3 with 21 isolates). Genealogies of four of the regions studied strongly supported the PS2 clade, composed of five Brazilian and one Venezuelan isolate. The second clade, PS3, composed solely of 21 Colombian isolates, was strongly supported by the alpha-tubulin genealogy. The remaining 38 individuals formed S1. Two of the three lineages of P. brasiliensis, S1 and PS2, are sympatric across their range, suggesting barriers to gene flow other than geographic isolation. Our study provides the first evidence for possible sexual reproduction in P. brasiliensis S1, but does not rule it out in the other two species.

The Effects of Nectar-Robbing on Fruit Production in Sparattosperma leucanthum (Bignoniaceae)

Many animals behave as robbers or thieves of floral resources, causing damage to floral tissues or consuming resources used to attract pollinators, or producing effects similar to emasculation by reducing the pollen load in the anthers (which generally results in losses in terms of sexual reproduction). The present work examined the direct and indirect impacts caused by nectar-robbing on the reproductive success of Sparattosperma leucanthum. Different manipulations of the flowers were tested to determine if fruit production was influenced by the perforations made in the floral tissues (direct damage), and if there were changes in visitation frequencies or in the behaviors of effective pollinators (indirect damage). Perforations made by nectar robbers did not lower the reproductive success of the plant species studied. The bee Trigona spinipes was the most frequent visitor and caused the largest perforations in the calyx and corolla of S. leucanthum. Additionally, we noted the occurrence of pollen theft by this same bee in flowers that had been protected against nectar-robbing. These results suggest that if S. leucanthum had developed a mechanism of resistance to robbery by T spinipes it would probably have experienced even lower pollination levels as a result of reductions in the quantities of pollen available for transfer by effective pollinators. We were not able to evaluate if nectar depletion through robbery modified the behavior of the effective pollinators (bumblebees of the genus Bombus).

Cytogenetics and embryology of Eupatorium laevigatum (Compositae)

Embryological studies indicate Eupatorium laevigatum to have Antennaria type diplospory with precocious embryony. The embryo sac is of the Polygonum type and the polar nuclei fuse before anthesis (maturation of the stamens). Endosperm development is autonomous and the central cell divides only after the initial stages of embryo formation. It is estimated that about 10% of the florets in anthesis contain an undivided egg which can be used for sexual reproduction. The study of microsporogenesis revealed abnormalities in chromosome pairing which result in the formation of univalents, bivalents, trivalents and higher polyvalents, with the consequent production of lagging chromosomes, unbalanced nuclei, micronuclei and sterile pollen. We found that, as represented by the material studied, E. laevigatum is an autohexaploid (2n = 6x = 60) in which each chromosome of a basic set of ten chromosomes is repeated six times and that E. laevigatum is an essentialy obligate apomictic.

Phenological aspects of Syngonanthus elegans (Bong.) Ruhl. (Eriocaulaceae) from Serra do Cipo - MG. Brazil

S. elegans (Eriocaulaceae) is known in Brazil as star flower and is used economically for ornamental purposes. The fact that there is no control over its collection, brings about great damage to its population. Thus the importance of phenologic data for the conservation of the species. This paper reports the marking of 60 individuals in three different phases of development and the collection of monthly data about their phenology. S. elegans is a perennial plant with a rhizomatous stem that characterizes its vegetative growth. The pubescent leaves present in plants can prevent heat loss and their pigments can raise the ultra-violet radiation absorption. The young leaves present in plants during the begining of the dry season use rhizome reserves. Hydric scarcity may be the main reason for the mortality of the species. Vegetative growth and sexual reproduction are very important for the population's survival.,The blooming period in S. elegans occurs from om February to July and the dispersal of seeds occurs from August to December.

The reproductive biology and cycle of Rioraja agassizi (Müller and Henle, 1841) (Chondrichthyes: Rajidae) in southeastern Brazil, SW Atlantic Ocean

Specimens of Rioraja agassizi were collected at Guarujá pier, São Paulo State, Brazil, from March 2005 to March 2006. A total of 275 males were captured. Based on the analysis of the clasper length, gonad weight, clasper gland length, alar thorns and lobule diameter, the size-at-maturity was estimated to be 32 cm. There were 1049 females in the record. Size-at-maturity was calculated in 40 cm. Sexual resting females were observed. Gonadosomatic and hepatosomatic indexes varied significantly in both sexes throughout the year. However, ovulation, egg-laying and presence of sperm in the seminal vesicle were observed all year round. For this reason, an annual cycle with at least one peak in the sexual activity is proposed for this species.

Thelytokous parthenogenesis in the fungus-gardening ant Mycocepurus smithii (Hymenoptera: Formicidae)

The general prevalence of sexual reproduction over asexual reproduction among organisms testifies to the evolutionary benefits of recombination, such as accelerated adaptation to changing environments and elimination of deleterious mutations. Documented instances of asexual reproduction in groups otherwise dominated by sexual reproduction challenge evolutionary biologists to understand the special circumstances that might confer an advantage to asexual reproductive strategies. Here we report one such instance of asexual reproduction in the ants. We present evidence for obligate thelytoky in the asexual fungus-gardening ant, Mycocepurus smithii, in which queens produce female offspring from unfertilized eggs, workers are sterile, and males appear to be completely absent. Obligate thelytoky is implicated by reproductive physiology of queens, lack of males, absence of mating behavior, and natural history observations. An obligate thelytoky hypothesis is further supported by the absence of evidence indicating sexual reproduction or genetic recombination across the species' extensive distribution range (Mexico-Argentina). Potential conflicting evidence for sexual reproduction in this species derives from three Mycocepurus males reported in the literature, previously regarded as possible males of M. smithii. However, we show here that these specimens represent males of the congeneric species M. obsoletus, and not males of M. smithii. Mycocepurus smithii is unique among ants and among eusocial Hymenoptera, in that males seem to be completely absent and only queens (and not workers) produce diploid offspring via thelytoky. Because colonies consisting only of females can be propagated consecutively in the laboratory, M. smithii could be an adequate study organism a) to test hypotheses of the population-genetic advantages and disadvantages of asexual reproduction in a social organism and b) inform kin conflict theory. For a Portuguese translation of the abstract, please see Abstract S1. © 2009 Rabeling et al.

The population genetic structure of Rhizoctonia solani AG-3PT from potato in the Colombian Andes

The soilborne fungus Rhizoctonia solani anastomosis group 3 (AG-3PT) is a globally important potato pathogen. However, little is known about the population genetic processes affecting field populations of R. solani AG-3PT, especially in the South American Colombian Andes, which is near the center of diversity of the two most common groups of cultivated potato, Solanum tuberosum and S. phureja. We analyzed the genetic structure of 15 populations of R. solani AG-3PT infecting potato in Colombia using 11 simple-sequence repeat (SSR) markers. In total, 288 different multilocus genotypes were identified among 349 fungal isolates. Clonal fractions within field populations were 7 to 33%. R ST statistics indicated a very low level of population differentiation overall, consistent with high contemporary gene flow, though moderate differentiation was found for the most distant southern populations. Genotype flow was also detected, with the most common genotype found widely distributed among field populations. All populations showed evidence of a mixed reproductive mode, including both asexual and sexual reproduction, but two populations displayed evidence of inbreeding. © 2013 The American Phytopathological Society.

Rhizoctonia solani AG-1: estrutura genética, etiologia e evolutibilidade nos agroecossitemas Brachiaria spp. e arroz na Colômbia

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeitos de inseticidas na sobrevivência e no comportamento de abelhas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Population Structure and Pathotype Diversity of the Wheat Blast Pathogen Magnaporthe oryzae 25 Years After Its Emergence in Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Low abundance of long-tongued pollinators leads to pollen limitation in four specialized hawkmoth-pollinated plants in the Atlantic Rain forest, Brazil

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

Estrutura genética de populações de Rhizoctonia oryzae-sativae do arroz em São Paulo, Brasil, e em meta, Colômbia, e potencial adaptativo do patógeno à Urochloa spp

Pós-graduação em Agronomia - FEIS

The urochloa foliar blight and collar rot pathogen rhizoctonia solani AG-1 IA emerged in South America via a host shift from rice

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

Pollination of Anemopaegma album (Bignoniaceae) with focus on floral nectar as the mediator of interactions with mutualistic and antagonistic bees

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)