Browsing by Issue Date, starting with "2003-07"
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- Filogeografia de Salamandra salamandra (Caudata Salamandridae) no sul de PortugalPublication . Caetano, Sofia Alexandra Ramos; Castilho, RitaA Salamandra salamandra constitui um complexo de subespécies distribuidas por toda a Europa. Em Portugal estão descrüas duas subespécies S.s. gallaica na maior parte do território português e S.s. crespoi na Serra de Monchique, embora os seus limites de distribuição geográfica estejam por identificar. Todos os registos referentes ao Sudeste de Portugal, apontam para a existência de um morfotipo intermédio entre S.s. crespor' e S.s. morenica na Serra Morena (Huelva, Espanha). O objectivo deste trabalho é definir os padrões de distribuição da S. salamandra no Sul de Portugal, por meios genéticos e reconstruir a principal sequência de acontecimentos que terão estado na origem desse padrão. O fragmento de 372 pares de bases do Citocromo b do ADN mitocondrial revelou-se uma boa ferramenta molecular na identificação das subespécies de salamandra, permitindo a identificação da zona de contacto entre as subespécies do Sul de Portugal. Propõe-se dois possiveis cenários de retracção populacional durante as eras glaciares e consequente re-colonização pós-glacial de S. salamandra no Sul de Portugal, cujas implicações são discutidas na distribuição actual das duas subespécies. Este trabalho serve já como ponto de comparação para futuras medidas de gestão e planeamento.
- Phylogeny of the moss family Bryaceae inferred from chloroplast DNA sequences and morphologyPublication . Pedersen, N.; Cox, C. J.; Hedenäs, LarsPhylogenetic relationships within the moss family Bryaceae were studied using chloroplast DNA sequences (atpB-rbcL, rpl16 intron, rps4, and trnL-trnF region) and anatomical and morphological data. Phylogenetic analyses using maximum parsimony, maximum likelihood, and Bayesian methods indicate that the genera Brachymenium, Bryum, and Rhodobryum are not monophyletic.
- Hormonal control of swimbladder sonic muscle dimorphism in the Lusitanian toadfish, Halobatrachus didactylusPublication . Modesto, Teresa; Canario, Adelino V. M.The swimbladder and associated sonic muscle of the Lusitanian toadfish Halobatrachus didactylus increase in size throughout life and are, respectively, 25% and 30% larger in type I (nest-holder) males than females, which may generate sexual differences in sound production. Sexual dimorphism in swimbladder is also evident in the morphological features of sonic muscle fibers. During the breeding season, type I males have smaller myofibril contracting zones surrounded by larger sarcoplasm areas compared with females, possibly an adaptation to speed and fatigue resistance for the production of long mating calls. Type II (floater) males show characteristics that are intermediate, but statistically not significantly different, between type I males and females. Six weeks after castration and androgen (testosterone and 11- ketotestosterone) replacement in type I and type II males there were no alterations either in swimbladder mass or fiber morphology. However, 17b-estradiol induced a significant decrease in swimbladder mass and sarcoplasm area/myofibril area ratio. Six months after castration there was a clear reduction in the seasonal swimbladder hypertrophy in males and induction of sonic fiber morphological characteristics that resemble those occurring in females (low sarcoplasm area/myofibril area ratio). These results suggest that testicular factors are required to initiate sonic muscle hypertrophy and type I sonic fiber phenotype in H. didactylus, but a specific involvement of androgens has not been completely clarified.
- Stress response of Listeria monocytogenes isolated from cheese and other foodsPublication . Faleiro, Maria Leonor; Andrew, Peter; Power, DeborahThe responses to pH and sodium chloride of four strains of Listeria monocytogenes isolated from Portuguese cheese, with a sodium chloride concentration of about 2% (w/v) and a pH value from 5.1 to 6.2, were studied. Two isolates from meat and two clinical isolates related to food-borne listeriosis, in which the implicated food product had about 2–3.5% (w/v) sodium chloride, also were studied. The effect of temperature on pH and sodium chloride sensitivity was also determined. The results show that natural isolates vary in response to these stresses and the data were often at variance with previously published data. Strains varied in sensitivity to low pH and to high sodium chloride concentration but the cheese isolates tended to be more resistant. A lower temperature was associated with a decrease in resistance to low pH and to sodium chloride. All strains showed an acid tolerance response induction when grown at pH 5.5 and although the time required for maximum induction of the response varied between strains, 2 h of acid adaptation, at least, was necessary which is longer than previously reported. Some strains showed an osmotolerance response after incubation in 3.5% (w/v) sodium chloride. Osmoadaptation, in addition to inducing an osmotolerance response, also induced cross-protection against acid shock conditions (pH 3.5). The acid tolerance response also induced a cross-protection against osmotic shock conditions (20% (w/v) sodium chloride). In some cases there was a relationship between the degree of resistance and adaptation, but usually the behaviour of a particular strain was independent of the conditions from which it was isolated.