ORCID Profile
0000-0002-3873-2042
Current Organisation
Universidade de São Paulo
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Publisher: Wiley
Date: 08-06-2018
DOI: 10.1002/JMOR.20834
Abstract: Evolutionary simplification of autopodial structures is a major theme in studies of body-form evolution. Previous studies on amniotes have supported Morse's law, that is, that the first digit reduced is Digit I, followed by Digit V. Furthermore, the question of reversibility for evolutionary digit loss and its implications for "Dollo's law" remains controversial. Here, we provide an analysis of limb and digit evolution for the skink genus Brachymeles. Employing phylogenetic, morphological, osteological, and myological data, we (a) test the hypothesis that digits have re-evolved, (b) describe patterns of morphological evolution, and (c) investigate whether patterns of digit loss are generalizable across taxa. We found strong statistical support for digit, but not limb re-evolution. The feet of pentadactyl species of Brachymeles are very similar to those of outgroup species, while the hands of these lineages are modified (2-3-3-3-2) and a have a reduced set of intrinsic hand muscles. Digit number variation suggests a more labile Digit V than Digit I, contrary to Morse's law. The observed pattern of digit variation is different from that of other scincid lizards (Lerista, Hemiergis, Carlia). Our results present the first evidence of clade-specific modes of digit reduction.
Publisher: The Company of Biologists
Date: 15-06-2004
DOI: 10.1242/JEB.01041
Abstract: Amphisbaenians are legless reptiles that differ significantly from other vertebrate lineages. Most species dig underground galleries of similar diameter to that of the animal. We studied the muscle physiology and morphological attributes of digging effort in the Brazilian hisbaenid Leposternon microcephalum (Squamata Amphisbaenia), which burrows by compressing soil against the upper wall of the tunnel by means of upward strokes of the head. The in iduals tested (& g) exerted forces on the soil of up to 24 N. These forces were possible because the fibres of the longissimus dorsi, the main muscle associated with burrowing, are highly pennated, thus increasing effective muscle cross-sectional area. The muscle is characterized by a metabolic transition along its length: proximal, medial and distal fibres are fast contracting and moderately oxidative, but fibres closer to the head are richer in citrate synthase and more aerobic in nature. Distal fibres, then, might be active mainly at the final step of the compression stroke, which requires more power. For animals greater than a given diameter,the work required to compress soil increases exponentially with body diameter. Leposternon microcephalum, and probably some other highly specialized hisbaenids, are most likely constrained to small diameters and can increase muscle mass and effective muscle cross-sectional area by increasing body length, not body diameter.
Publisher: The Company of Biologists
Date: 03-2004
DOI: 10.1242/JEB.00870
Abstract: Tropidurid lizards have colonized a variety of Brazilian open environments without remarkable morphological variation, despite ecological and structural differences among habitats used. This study focuses on two Tropidurussister-species that, despite systematic proximity and similar morphology,exhibit great ecological ergence and a third ecologically generalist congeneric species providing an outgroup comparison. We quantified jumping capacity and sprint speed of each species on sand and rock to test whether ecological ergence was also accompanied by differences in locomotor performance. Relevant physiological traits possibly associated with locomotor performance – metabolic scopes and fiber type composition, power output and activity of the enzymes citrate synthase, pyruvate kinase and lactate dehydrogenase of the iliofibularis muscle – were also compared among the three Tropidurus species. We found that the two sister-species exhibited remarkable differences in jumping performance, while Tropidurus oreadicus, the more distantly related species, exhibited intermediate values. Tropidurus psamonastes, a species endemic to sand dunes,exhibited high absolute sprint speeds on sand, jumped rarely and possessed a high proportion of glycolytic fibers and low activity of citrate synthase. The sister-species Tropidurus itambere, endemic to rocky outcrops,performed a large number of jumps and achieved lower absolute sprint speed than T. psamonastes. This study provides evidence of rapid ergence of locomotor parameters between sister-species that use different substrates,which is only partially explained by variation in physiological parameters of the iliofibularis muscle.
Publisher: Springer Science and Business Media LLC
Date: 08-06-2004
DOI: 10.1007/S00360-004-0431-7
Abstract: Interin idual analyses of physiological performance represent one of the most powerful tools for identifying functional positive and negative linkages between various performance traits. In this study we investigated functional linkages in the whole-gastrocnemius performance of juvenile Bufo viridis by examining interin idual variation in in vitro muscle performance and muscle fibre-type composition. We used the work-loop technique to investigate the maximum in vitro power output and fatigue resistance of the gastrocnemius muscle during repeated sets of three cycles at the cycle frequency of 5 Hz, simulating an intermittent style of locomotion. We found several significant correlations between different measures of in vitro muscle performance, including a negative correlation between maximum net power output and fatigue resistance of power, indicating functional trade-offs between these performance traits. We also investigated the extent of in idual variation in the proportions of different fibre types, and tested for correlations between in idual variation in muscle fibre-type composition and the previously measured isolated muscle performance. Fast glycolytic fibres represented 84.0 +/- 3.4% of the muscle, while the combined slow oxidative and fast oxidative-glycolytic fibres represented 16 +/- 3.4%. We found no significant correlations between measures of in vitro muscle performance and the proportion of different fibre types in the gastrocnemius muscle. However, despite this lack of correlation between whole-muscle performance and muscle fibre-type composition data, we suggest the functional linkages detected between different measures of in vitro muscular performance have important ecological and evolutionary consequences.
Publisher: University of Chicago Press
Date: 09-2005
DOI: 10.1086/432149
Abstract: Frog jumping is an excellent model system for examining the structural basis of interin idual variation in burst locomotor performance. Some possible factors that affect jump performance, such as total body size, hindlimb length, muscle mass, and muscle mechanical and biochemical properties, were analysed at the interin idual (intraspecies) level in the tree frog Hyla multilineata. The aim of this study was to determine which of these physiological and anatomical variables both vary between in iduals and are correlated with interin idual variation in jump performance. The model produced via stepwise linear regression analysis of absolute data suggested that 62% of the interin idual variation in maximum jump distance could be explained by a combination of interin idual variation in absolute plantaris muscle mass, total hindlimb muscle mass (excluding plantaris muscle), and pyruvate kinase activity. When body length effects were removed, multiple regression indicated that the same independent variables explained 43% of the residual interin idual variation in jump distance. This suggests that in iduals with relatively large jumping muscles and high pyruvate kinase activity for their body size achieved comparatively large maximal jump distances for their body size.
No related grants have been discovered for Tiana Kohlsdorf.