Eulalia Moreno

Leg Morphology and Feeding Postures in Four Parus Species: An Experimental Ecomorphological Approach

.-lbstract. The foraging behavior of four Parus species feeding at artificial feeders was studied. while controlling for ecological variables related to patch characteristics (food quality. food access. and escape distance to the nearest refuge). Hindlimb morphology (osteology and myology) was analyzed and compared with foraging postures at feeders. Using the Long-Tailed Tit as an appropriate outgroup for comparison. and considering functional changes associated with morphological changes. we demonstrated the existente of clear ecomorphological patterns relating foraging postures and hindlimb morphology in the four Parus species studied. The Blue Tit uses hanging postures preferably and its hindlimb morphology is modified for helping leg flexion. The Crested Tit more often stands and its hindlimb morphology is modified to aid leg extension. Great and Coa1 Tits are ecologically and morphologically intermediate between the two former species. Our results show morphology as a determinant of locomotion mode. Since foraging postures are tightly associated with substrate use. then morphology should be considered when studying pressures determining community organization. Our proposed integrative method for dealing with ecomorphology can be valuable in demonstrating the adaptiveness of morphological structures in phylogenetically and ecologically related species. Kej. words: ~ornorpliolog~~; fec~Iirzg postures: hindlirnb; rnorpholoyl.; rnj~olo~~; ostrologj,: Parus:

Half-life of the plasma membrane ATPase and its activating system in resting yeast cells

The stability of the yeast plasma membrane ATPase and its activating system has been investigated in resting Saccharomyces cerevisiae. The half-life of ATPase in the presence of glucose is about 11 h whereas in the presence of ethanol it is greater than 30 h. In the case of the ATPase activating system half-life values of about 5 and 14 h have been observed, respectively, in the presence of these substrates. These results indicate that, similarly to sugar transport systems, plasma membrane ATPase as well as its activating system are less stable than the bulk of proteins in this organism. The fact that all plasma membrane proteins so far examined show low half-life values suggests that a low stability could be a general characteristic of these proteins.

Internal Trehalose Protects Endocytosis from Inhibition by Ethanol in Saccharomyces cerevisiae

ABSTRACT Endocytosis in Saccharomyces cerevisiae is inhibited by concentrations of ethanol of 2 to 6% (vol/vol), which are lower than concentrations commonly present in its natural habitats. In spite of this inhibition, endocytosis takes place under enological conditions when high concentrations of ethanol are present. Therefore, it seems that yeast has developed some means to circumvent the inhibition. In this work we have investigated this possibility. We identified two stress conditions under which endocytosis was resistant to inhibition by ethanol: fermentation during nitrogen starvation and growth on nonfermentable substrates. Under these conditions, yeast accumulates stress protectors, primarily trehalose and Hsp104, a protein required for yeast to survive ethanol stress. We found the following. (i) The appearance of ethanol resistance was accompanied by trehalose accumulation. (ii) Mutant cells unable to synthesize trehalose also were unable to develop resistance. (iii) Mutant cells that accumulated trehalose during growth on sugars were resistant to ethanol even under this nonstressing condition. (iv) Mutant cells unable to synthesize Hsp104 were able to develop resistance. We conclude that trehalose is the major factor in the protection of endocytosis from ethanol. Our results suggest another important physiological role for trehalose in yeast.

Morphological Evolution of Spiders Predicted by Pendulum Mechanics

Background Animals have been hypothesized to benefit from pendulum mechanics during suspensory locomotion, in which the potential energy of gravity is converted into kinetic energy according to the energy-conservation principle. However, no convincing evidence has been found so far. Demonstrating that morphological evolution follows pendulum mechanics is important from a biomechanical point of view because during suspensory locomotion some morphological traits could be decoupled from gravity, thus allowing independent adaptive morphological evolution of these two traits when compared to animals that move standing on their legs; i.e., as inverted pendulums. If the evolution of body shape matches simple pendulum mechanics, animals that move suspending their bodies should evolve relatively longer legs which must confer high moving capabilities. Methodology/Principal Findings We tested this hypothesis in spiders, a group of diverse terrestrial generalist predators in which suspensory locomotion has been lost and gained a few times independently during their evolutionary history. In spiders that hang upside-down from their webs, their legs have evolved disproportionately longer relative to their body sizes when compared to spiders that move standing on their legs. In addition, we show how disproportionately longer legs allow spiders to run faster during suspensory locomotion and how these same spiders run at a slower speed on the ground (i.e., as inverted pendulums). Finally, when suspensory spiders are induced to run on the ground, there is a clear trend in which larger suspensory spiders tend to run much more slowly than similar-size spiders that normally move as inverted pendulums (i.e., wandering spiders). Conclusions/Significance Several lines of evidence support the hypothesis that spiders have evolved according to the predictions of pendulum mechanics. These findings have potentially important ecological and evolutionary implications since they could partially explain the occurrence of foraging plasticity and dispersal constraints as well as the evolution of sexual size dimorphism and sociality.

Morphological evolution and changes in foraging behaviour of island and mainland populations of Blue Tit (Parus caeruleus) - a test of convergence and ecomorphological hypotheses

SummaryWe study the leg morphology and feeding postures of two subspecies of the Blue Tit (Parus caeruleus; Tenerife island and the Iberian Peninsula) and the Coal Tit (Parus ater; Iberian Peninsula). We search for evidence supporting the hypothesis of convergent evolution in morphological and ecological traits and we discuss the role of ecomorphological hypotheses as predictors of foraging differences at the intraspecific level. To overcome the problems introduced by environmental characteristics not related to locomotion and competition, we make observations under controlled situations to manage food quality and food access. We determine that the island Blue Tit has a longer tarsometatarsus, larger foot span and a more proximal insertion of the tibialis cranialis muscle (flexor of the tarsometatarsus) than the mainland Blue Tit. These morphological differences are consistent with the more frequent use of hanging and clinging ‘head-up’ postures by the Iberian Blue Tit. Several ecomorphological hypotheses obtained at the interspecific level with other taxa, have proved to be of high predictive value for explaining ecological differences considering morphological evolution. The Tenerife Blue Tit and the Iberian Coal Tit clearly show close convergence in both feeding postures and leg structure, although some differences in morphology were found between these two species. Convergence in foraging methods between the island Blue Tit and the mainland Coal Tit can be explained without considering current interspecific competition as a determinant of niche space.

Low prevalence of haematozoa in Trumpeter finches Bucanetes githagineus from south-eastern Spain: additional support for a restricted distribution of blood parasites in arid lands

We have investigated the prevalence of avian haematozoa in Trumpeter finches at two localities situated in arid habitats. This study reports the first record of infection for this bird species. Two out of 58 individuals were infected by Leucocytozoon sp. We discuss several hypotheses accounting for low parasitemia in arid bird species.

Should congruence between intra- and interspecific ecomorphological relationships be expected? A case study with the great tit, Parus major

We studied the relationship between leg morphology and posture while feeding in a population of great tits (Parus major) under controlled conditions to investigate to what extent morphology and ecology are linked at the individual level. From predictions generated at the interspecific level within the genus Parus (Moreno and Carrascal 1993), we tested whether intra– and interspecific ecomorphological relationships are consistent. Within our population, neither leg bone lengths nor leg muscle morphology were related to the feeding posture of individuals. However, differences in body weight were correlated with inter–individual differences in time spent hanging. These results demonstrate that the association between intra– and interspecific ecomorphological relationships is not uniform. We argue that, at the intraspecific level, body weight overrides the significance of other traits that have a functional meaning at the interspecific level (i.e. leg segment lengths, muscular morphology), due to isometric variation of morphological traits (muscular and skeletal) with body mass. Thus, the discrepancy between the ecomorphological associations at intra– and interspecific levels is the result of a problem of scale (morphological changes in evolutionary time and isometric variation of morphological traits with body mass in ecological time).

Thriving in an arid environment: High prevalence of avian lice in low humidity conditions

ABSTRACT Abiotic factors have been reported to cause variation in parasite pressure among host populations, but such relationships have not been studied in detail, and conflicting evidence exists about the nature of these relationships. Here we study within- and between-population variation in chewing lice parasitization in an arid bird species, the Trumpeter finch (Bucanetes githagineus), and the influence of ambient humidity on parasite load. We found a high prevalence of 2 chewing lice even in particularly dry years and a positive effect of humidity on prevalence at a monthly scale. Nonetheless, our results clearly reveal that lice can become abundant at low ambient humidity conditions and that birds in arid environments are not necessarily under lower ectoparasitic pressure than birds in humid regions. We suggest that lice may adapt their life cycle to overcome the most critical period by synchronizing the more resistant phase (eggs) to the period when relative humidity is lowest (i.e., summertime). We stress that studies on the effect of ecological factors on host–parasite relationships should consider detailed aspects of the life cycle of the latter and the main biological traits of the different stages of the parasites.

Role of the Cytoskeleton in Endocytosis of the Yeast Maltose Transporter

Certain components of the cytoskeleton play a role in yeast fluid‐phase endocytosis as well as in endocytosis of the α‐factor when this pheromone is bound to its 7‐transmembrane segment receptor. The yeast maltose transporter is a 12‐transmembrane segment protein that, under certain physiological conditions, is degraded in the vacuole after internalization by endocytosis. In this work, the possible role of the cytoskeleton in endocytosis of this transporter has been investigated. Using mutants defective in β‐tubulin, actin and the actin‐binding proteins Sac6 and Abp85, as well as nocodazole, which inhibits formation of microtubules, we have shown that actin microfilaments are involved in endocytosis of the maltose transporter whereas microtubules are not.© 1997 John Wiley & Sons, Ltd.

Cell-mediated immune response affects food intake but not body mass: An experiment with wintering great tits

Abstract: Reduction in body mass is one of the major energetic costs associated with immune challenge. In studies where such findings have been obtained, birds performed their normal activities in a natural environment during the experiments. In such situations food intake after immune challenge was not controlled. Therefore, reduction in body mass could be due to a reduction in foraging activity through difficulties in searching for and finding food. The aim of the present study is to determine whether an immune challenge affects body mass or food intake in wintering great tits maintained in captivity. Ten individuals were kept in an outdoor aviary during the experiments. Cell-mediated immunity was determined by the wing web index using phytohemagglutinin (PHA) injection. Body mass and food intake were measured before and after PHA injection. We found no difference in body mass between pre- and post-PHA injection. However, we found a significant increase in the amount of food intake after PHA injection compared with food intake before injection. Moreover, the magnitude of the immune response, measured by the wing web index, was positively related to the amount of food intake. In conclusion, our results suggest that the immune response to PHA is a costly task for small birds during winter and that this cost is compensated for by the increase in food intake.