The implications of bite performance for diet in two species of lacertid lizards

2001 ◽  
Vol 79 (4) ◽  
pp. 662-670 ◽  
Author(s):  
A Herrel ◽  
R Van Damme ◽  
B Vanhooydonck ◽  
F De Vree
Keyword(s):  
Resource Use ◽  
Food Resource ◽  
Head Shape ◽  
Podarcis Muralis ◽  
Biomechanical Models ◽  
Lacertid Lizards ◽  
Study Support ◽  
Dietary Shifts ◽  
Ecological Variable

One of the performance features that is generally considered crucial to increasing the potential prey spectrum of lizards is bite capacity. In this study we tested whether bite forces may serve as a basis for diet selection in two syntopically occurring lacertid lizards. We did so by measuring bite forces in vivo for a large sample of lizards of the species Podarcis muralis and Lacerta vivipara. To assess the ecological relevance of the bite forces, we tested the hardness of a number of natural prey items of both species. The results of our study support the predictions of biomechanical models of biting in lizards and indicate that both larger animals and larger headed ones bite harder. Surprisingly, head shape is an excellent predictor of bite performance in the species studied. Moreover, it is demonstrated that bite capacity is a potentially important ecological variable that could be used as a factor in explaining patterns of food-resource use, ontogenetic dietary shifts, and sexual dimorphism in diet.

scholarly journals In vitro analysis of elongation and termination by mutant RNA polymerases with altered termination behavior.

1996 ◽  
Vol 16 (11) ◽  
pp. 6468-6476 ◽  
Author(s):  
S A Shaaban ◽  
E V Bobkova ◽  
D M Chudzik ◽  
B D Hall
Keyword(s):  
Rna Polymerase Iii ◽  
Multiple Roles ◽  
Wild Type ◽  
Protein Motifs ◽  
Study Support ◽  
Vitro Analysis ◽  
Pol Iii ◽  
In Vitro Analysis

We have studied the in vitro elongation and termination properties of several yeast RNA polymerase III (pol III) mutant enzymes that have altered in vivo termination behavior (S. A. Shaaban, B. M. Krupp, and B. D. Hall, Mol. Cell. Biol. 15:1467-1478, 1995). The pattern of completed-transcript release was also characterized for three of the mutant enzymes. The mutations studied occupy amino acid regions 300 to 325, 455 to 521, and 1061 to 1082 of the RET1 protein (P. James, S. Whelen, and B. D. Hall, J. Biol. Chem. 266:5616-5624, 1991), the second largest subunit of yeast RNA pol III. In general, mutant enzymes which have increased termination require a longer time to traverse a template gene than does wild-type pol III; the converse holds true for most decreased-termination mutants. One increased-termination mutant (K310T I324K) was faster and two reduced termination mutants (K512N and T455I E478K) were slower than the wild-type enzyme. In most cases, these changes in overall elongation kinetics can be accounted for by a correspondingly longer or shorter dwell time at pause sites within the SUP4 tRNA(Tyr) gene. Of the three mutants analyzed for RNA release, one (T455I) was similar to the wild type while the two others (T455I E478K and E478K) bound the completed SUP4 pre-tRNA more avidly. The results of this study support the view that termination is a multistep pathway in which several different regions of the RET1 protein are actively involved. Region 300 to 325 likely affects a step involved in RNA release, while the Rif homology region, amino acids 455 to 521, interacts with the nascent RNA 3' end. The dual effects of several mutations on both elongation kinetics and RNA release suggest that the protein motifs affected by them have multiple roles in the steps leading to transcription termination.

scholarly journals Patterns of food resource use by two congeneric species of piranhas (Serrasalmus) on the upper Paraná river floodplain

2003 ◽  
Vol 63 (2) ◽  
pp. 177-182 ◽  
Author(s):  
C. S. Agostinho ◽  
N. S. Hahn ◽  
E. E. Marques
Keyword(s):  
Resource Use ◽  
Native Species ◽  
Feeding Strategy ◽  
Food Resource ◽  
Paraná River ◽  
Activity Period ◽  
Parana River ◽  
Invading Species ◽  
Upper Paraná River Floodplain ◽  
Upper Paraná River

Serrasalmus marginatus invaded the Upper Paraná River after construction of the Itaipu Dam in November 1982. This was followed by a reduction in abundance of the native species S. spilopleura. Analysis of the pattern of food resource use revealed that both species employ the same feeding strategy, eating mainly fish (whole fish or muscle fragments) and fins bitten off their prey. The diurnal activity period and the feeding rhythm were better-defined in S. marginatus. For young individuals of both species, food was taken in a significantly discontinuous manner (F = 2.83; p < 0.05 and F = 13.25; p < 0.05), with a peak at 4 p.m. Ontogenetic differences in diet, the strong feeding overlap of larger individuals of S. marginatus and smaller individuals of S. spilopleura, and the aggressiveness of S. marginatus in establishing feeding territories may have contributed to the success of the invading species.

Sensitivity of Neck Musculoskeletal Model Predictions to Variation in Intervertebral Kinematics

2013 ◽  
Author(s):  
Derek D. Nevins ◽  
Liying Zheng ◽  
Anita N. Vasavada
Keyword(s):  
Sagittal Plane ◽  
Center Of Mass ◽  
Chronic Neck Pain ◽  
Neck Muscle ◽  
Neck Extension ◽  
In Vivo Measurement ◽  
Biomechanical Models ◽  
Neck Strength ◽  
Flexion Strength

In-vivo measurement of loads and displacements in the head and neck is very difficult. Musculoskeletal biomechanical models are useful tools for investigating biomechanical phenomena in this system, but they require several assumptions and simplifications regarding tissue mechanical properties and intervertebral kinematics (IVK). In particular, IVK show considerable variation among subjects [1], and quantifying the influence of this variation on model estimates is important for the application of models toward understanding neck biomechanical function. Variation in IVK parameters may affect model estimates of neck strength (neck muscle moment, the product of muscle force and muscle moment arm), as well as the location of the head center of mass, which influences the gravitational load on the neck due to the weight of the head. The magnitude of gravitational load relative to neck extension strength, referred to here as fatiguability, is an estimate of demand on neck muscles and may be related to chronic neck pain induced by forward head postures [2]. The goal of this study was to quantify variation in model estimates of flexion strength, extension strength and fatigability over sagittal plane postures, due to variation in IVK.

scholarly journals Characterization of rat tail lymphatic contractility and biomechanics: incorporating nitric oxide-mediated vasoregulation

2020 ◽  
Vol 17 (170) ◽  
pp. 20200598 ◽  
Author(s):  
Mohammad S. Razavi ◽  
J. Brandon Dixon ◽  
Rudolph L. Gleason
Keyword(s):  
Nitric Oxide ◽  
Mechanical Response ◽  
Contractile Function ◽  
Ex Vivo ◽  
Biomechanical Model ◽  
Biomechanical Models ◽  
Lymphatic Pumping ◽  
Rat Tail ◽  
Lymphatic Contractility

The lymphatic system transports lymph from the interstitial space back to the great veins via a series of orchestrated contractions of chains of lymphangions. Biomechanical models of lymph transport, validated with ex vivo or in vivo experimental results, have proved useful in revealing novel insight into lymphatic pumping; however, a need remains to characterize the contributions of vasoregulatory compounds in these modelling tools. Nitric oxide (NO) is a key mediator of lymphatic pumping. We quantified the active contractile and passive biaxial biomechanical response of rat tail collecting lymphatics and changes in the contractile response to the exogenous NO administration and integrated these findings into a biomechanical model. The passive mechanical response was characterized with a three-fibre family model. Nonlinear regression and non-parametric bootstrapping were used to identify best-fit material parameters to passive cylindrical biaxial mechanical data, assessing uniqueness and parameter confidence intervals; this model yielded a good fit ( R 2 = 0.90). Exogenous delivery of NO via sodium nitroprusside (SNP) elicited a dose-dependent suppression of contractions; the amplitude of contractions decreased by 30% and the contraction frequency decreased by 70%. Contractile function was characterized with a modified Rachev–Hayashi model, introducing a parameter that is related to SNP concentration; the model provided a good fit ( R 2 = 0.89) to changes in contractile responses to varying concentrations of SNP. These results demonstrated the significant role of NO in lymphatic pumping and provide a predictive biomechanical model to integrate the combined effect of mechanical loading and NO on lymphatic contractility and mechanical response.

scholarly journals Spatial, seasonal and ontogenetic changes in food resource use by a piscivore fish in two Pantanal lagoons, Brazil

2013 ◽  
Vol 11 (1) ◽  
pp. 163-170 ◽  
Author(s):  
Michele de Faveri Gimenes ◽  
Rosemara Fugi ◽  
Andréia Isaac ◽  
Marlene Rodrigues da Silva
Keyword(s):  
Resource Use ◽  
Pearson Correlation ◽  
Food Resource ◽  
Morphological Characteristics ◽  
Immature Stages ◽  
Ontogenetic Changes ◽  
Strong Negative Correlation ◽  
Use Of Resources ◽  
Spearman Coefficient ◽  
Flood Period

We evaluated the factors that affect the food resource use by Plagioscion ternetzi using three approaches: spatial, seasonal, and ontogenetic changes. Fish were sampled between March 2000 and February 2001 and March 2003 and February 2004 in the Sinhá Mariana and Chacororé lagoons, wetlands of the Pantanal Matogrossense. Fish was the predominant food in the diet, but shrimps and insects have been also consumed. The diet of P. ternetzi was significantly different between lagoons, but no difference was detected between dry and flood periods. In Sinhá Mariana lagoon, the diet mainly consisted of Psectrogaster curviventris, in both periods. In the flood period in Chacororé lagoon, fish was the dominant food (especially Astyanax spp., Leporinus spp. and Schizodon borellii), and in dry, shrimp and Eigenmannia spp. The Spearman coefficient indicated no correlation between the abundance of caught fish species and their abundances in the diet of P. ternetzi in Sinhá Mariana lagoon, and a strong negative correlation at Chacororé lagoon, although some very consumed preys were numerically abundant in the environment. Despite the intake of insect and shrimp, P. ternetzi was piscivorous since immature stages. A correlation between each item and the size classes of P. ternetziwas tested by means of Pearson correlation that showed that the changes in the use of resources over ontogenetic development have been represented by increased intake of P. curviventris in Mariana lagoon, and S. borellii at Chacororé lagoon, accompanying the increase in the size of the predator. In this way, the results suggest that several factors can be involved in the use of food resources by P. ternezi, among them the abundance, the size and morphological characteristics of the prey.

Food resource use in a tropical eastern Pacific tidepool fish assemblage

2008 ◽  
Vol 153 (6) ◽  
pp. 1023-1035 ◽  
Author(s):  
Gustavo Adolfo Castellanos-Galindo ◽  
Alan Giraldo
Keyword(s):  
Resource Use ◽  
Fish Assemblage ◽  
Food Resource ◽  
Eastern Pacific ◽  
Tropical Eastern Pacific

Genetic and phenotypic component in head shape of common wall lizard Podarcis muralis

2016 ◽  
Vol 37 (3) ◽  
pp. 301-310 ◽  
Author(s):  
Roberto Sacchi ◽  
Marco Mangiacotti ◽  
Stefano Scali ◽  
Michele Ghitti ◽  
Beatrice Bindolini ◽  
...  
Keyword(s):  
Natural Selection ◽  
Morphological Differentiation ◽  
Phenotypic Change ◽  
Adaptive Responses ◽  
Head Shape ◽  
Heritable Variation ◽  
Podarcis Muralis ◽  
Environmental Pressures ◽  
Common Wall ◽  
Wide Range

Head shape in lizards correlates with a wide range of environmental pressures, supporting the hypothesis that patterns of phenotypic change represent adaptive responses to selective processes. However, natural selection promotes evolutionary adaptation only if the trait under selection has enough heritable variation. In this study we used geometric morphometrics and quantitative genetics to assess the heritability patterns of the head shape and size of common wall lizards (Podarcis muralis). Genetic and phenotypic components were estimated using animal models, which showed that more than half of the variation in head morphology is inheritable. Furthermore, at least five independent patterns of genetically determined phenotypic change were detected. These outcomes confirm that morphological differentiation in common wall lizards may reliably be regarded as the result of adaptive processes driven by natural selection.

scholarly journals Distinctive properties of Arabidopsis SUMO paralogues support the in vivo predominant role of AtSUMO1/2 isoforms

2011 ◽  
Vol 436 (3) ◽  
pp. 581-590 ◽  
Author(s):  
Laura Castaño-Miquel ◽  
Josep Seguí ◽  
L. Maria Lois
Keyword(s):  
Protein Modification ◽  
Molecular Mechanisms ◽  
Sumo Conjugation ◽  
Thioester Bond ◽  
Study Support ◽  
Non Covalent Interactions ◽  
Enzyme Recognition ◽  
Covalent Interactions

Protein modification by SUMO (small ubiquitin-related modifier) has emerged as an essential regulatory mechanism in eukaryotes. Even though the molecular mechanisms of SUMO conjugation/deconjugation are conserved, the number of SUMO machinery components and their degree of conservation are specific to each organism. In the present paper, we show data contributing to the notion that the four expressed Arabidopsis SUMO paralogues, AtSUMO1, 2, 3 and 5, have functionally diverged to a higher extent than their human orthologues. We have explored the degree of conservation of these paralogues and found that the surfaces involved in E1-activating enzyme recognition, and E2-conjugating enzyme and SIM (SUMO-interacting motif) non-covalent interactions are well conserved in AtSUMO1/2 isoforms, whereas AtSUMO3 shows a lower degree of conservation, and AtSUMO5 is the most divergent isoform. These differences are functionally relevant, since AtSUMO3 and 5 are deficient in establishing E2 non-covalent interactions, which has not been reported for any naturally occurring SUMO orthologue. In addition, AtSUMO3 is less efficiently conjugated than AtSUMO1/2, and AtSUMO5 shows the lowest conjugation level. A mutagenesis analysis revealed that decreases in conjugation rate and thioester-bond formation are the result of the non-conserved residues involved in E1-activating enzyme recognition that are present in AtSUMO3 and 5. The results of the present study support a role for the E1-activating enzyme in SUMO paralogue discrimination, providing a new mechanism to favour conjugation of the essential AtSUMO1/2 paralogues.

scholarly journals Does aquatic foraging impact head shape evolution in snakes?

2016 ◽  
Vol 283 (1837) ◽  
pp. 20161645 ◽  
Author(s):  
Marion Segall ◽  
Raphaël Cornette ◽  
Anne-Claire Fabre ◽  
Ramiro Godoy-Diana ◽  
Anthony Herrel
Keyword(s):  
Aquatic Environment ◽  
Anterior Part ◽  
Three Dimensional ◽  
Shape Evolution ◽  
Head Shape ◽  
Evolutionary Trajectory ◽  
Biomechanical Models ◽  
Historical Factors ◽  
Evolutionary Trajectories ◽  
Do So

Evolutionary trajectories are often biased by developmental and historical factors. However, environmental factors can also impose constraints on the evolutionary trajectories of organisms leading to convergence of morphology in similar ecological contexts. The physical properties of water impose strong constraints on aquatic feeding animals by generating pressure waves that can alert prey and potentially push them away from the mouth. These hydrodynamic constraints have resulted in the independent evolution of suction feeding in most groups of secondarily aquatic tetrapods. Despite the fact that snakes cannot use suction, they have invaded the aquatic milieu many times independently. Here, we test whether the aquatic environment has constrained head shape evolution in snakes and whether shape converges on that predicted by biomechanical models. To do so, we used three-dimensional geometric morphometrics and comparative, phylogenetically informed analyses on a large sample of aquatic snake species. Our results show that aquatic snakes partially conform to our predictions and have a narrower anterior part of the head and dorsally positioned eyes and nostrils. This morphology is observed, irrespective of the phylogenetic relationships among species, suggesting that the aquatic environment does indeed drive the evolution of head shape in snakes, thus biasing the evolutionary trajectory of this group of animals.

scholarly journals IMMUNOLOGIC RELATIONS AMONG VARIOUS ANIMAL COLLAGENS

1965 ◽  
Vol 122 (3) ◽  
pp. 441-454 ◽  
Author(s):  
Sidney Rothbard ◽  
Robert F. Watson
Keyword(s):  
Guinea Pig ◽  
Tissue Specificity ◽  
Complement Fixation ◽  
Basement Membranes ◽  
Complete Agreement ◽  
Cross Reactions ◽  
Absorption Studies ◽  
Cross Absorption ◽  
Study Support

By the use of complement fixation and in vivo immunofluorescence with cross-absorption studies it was shown that acid soluble collagens prepared from rat, mouse, guinea pig, chicken, carp, and man exhibit species specificity. Rat and mouse collagens were found to be indistinguishable and to cross-react with guinea pig collagen. Cross-reactions also occurred between the collagens of rat and man and chicken and man. Tissue specificity, or an antigen common to all of the collagens, was not demonstrated. There was complete agreement in the results of the two immunologic methods. The findings in this study support the conclusion that collagen in some form is present in the renal glomerular basement membranes.

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