Seasonal changes in parasite load and a cellular immune response in a colour polymorphic lizard

Permanent colour polymorphisms may be maintained by complex interactions between physiological traits (e.g. immunity) and environmental pressures. In this study we investigate morph specific variation in parasite load and cellular immune response (induced by a Phytohaemagglutinin, PHA injection) in a colour polymorphic population of the Dalmatian wall lizard (Podarcis melisellensis), where adult males have bright white, yellow or orange throats and ventral sides. Orange males have larger heads and can bite harder than the others. To examine seasonal effects, analyses were performed at an early and late stage in the reproductive season (May and September). Infection with mites and ticks did not differ among morphs, but was more severe at the end of the reproductive season. Fewer orange individuals were infected with haemogregarines at the end of the season, but white males were always more infected (higher number of haemogregarines in their blood) than other morphs. White and yellow males showed an increased PHA response towards the end of the season, but PHA response decreased in the orange morph. Finally, across all morphs, a relationship was found between ectoparasite load and PHA response. Our study provides indications of alternative life-history strategies among colour morphs and evidence for an up-regulation of the immune function at the end of the reproductive season.     

No trade-off between sprinting and climbing in two populations of the Lizard Podarcis hispanica (Reptilia: Lacertidae).

Biomechanical reflections suggest that lizards that have specialized in running should differ in parts of their morphological design from lizards that have specialized in climbing. Moreover, adaptation in one direction may conflict with performance in the other. We tested this assumed trade-off by measuring climbing and running performance in two subspecies of the Mediterranean lizard Poaarcis hispanica. One subspecies, P. h. atrata , inhabits a number of small islets near the Spanish coast. It is mainly ground dwelling. The other subspecies, P. h. hispanica , was sampled on the mainland of Spain. It frequendy occupies vertical elements within its habitat. Our data do not support the notion of a trade-off between both types of locomotion. Individuals of P. h. hispanica both run and climb faster than those of P. h. atrata. There is no difference between subspecies in ability to cling onto tilted substrates. Predictions on the morphology of both subspecies, inspired by biomechanical arguments, are not supported by our measurements.     

In vitro selection and characterization of DNA aptamers recognizing chloramphenicol

Chloramphenicol (Cam), although an effective antibiotic, has lost favour due to some fatal side effects. Thus there is an urgent need for rapid and sensitive methods to detect residues in food, feed and environment. We engineered DNA aptamers that recognize Cam as their target, by conducting in vitro selections. Aptamers are nucleic acid recognition elements that are highly specific and sensitive towards their targets and can be synthetically produced in an animal-friendly manner, making them ethical innovative alternatives to antibodies. None of the isolated aptamers in this study shared sequence homology or structural similarities with each other, indicating that specific Cam recognition could be achieved by various DNA sequences under the selection conditions used. Analyzing the binding affinities of the sequences, demonstrated that dissociation constants (K_d) in the extremely low micromolar range, which were lower than those previously reported for Cam-specific RNA aptamers, were achieved. The two best aptamers had G rich (>35%) nucleotide regions, an attribute distinguishing them from the rest and apparently responsible for their high selectivity and affinity (K_d ∼ 0.8 and 1 μM respectively). These aptamers open up possibilities to allow easy detection of Cam via aptamer-based biosensors.     

The effects of substratum on locomotor performance in lacertid lizards

Locomotion is important to animals because it has direct implications for fitness through its role in predator escape, prey capture, and territory defence. Despite significant advances in our understanding of animal locomotion, studies exploring how substrate properties affect locomotor performance remain scant. In the present study, we explore how variation in substrate (sand, slate, cork) affects locomotor performance in lacertid lizards that differ in morphology. Moreover, we explore whether substrate effects are the same for different types of locomotor performance (speed, acceleration, and stamina). Our results show that the substrate affected most types of locomotor performance studied but not always in the same way. Although substrate effects were species‐dependent for the maximal speed over 50 cm and the distance run to exhaustion, this was not the case for acceleration capacity. These results suggest that substrate texture differentially affects burst performance vs. longer duration measures of locomotor performance. Finally, straightforward relationships between habitat use and the substrate on which performance was maximized were not observed. This suggests that the evolution of locomotor capacity is complex and that animals may show compromise phenotypes allowing them to deal with a variety of substrates in their natural environment. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●●, ●●–●●.     

Targeted resequencing of HIV variants by microarray thermodynamics

Within a single infected individual, a virus population can have a high genomic variability. In the case of HIV, several mutations can be present even in a small genomic window of 20–30 nucleotides. For diagnostics purposes, it is often needed to resequence genomic subsets where crucial mutations are known to occur. In this article, we address this issue using DNA microarrays and inputs from hybridization thermodynamics. Hybridization signals from multiple probes are analysed, including strong signals from perfectly matching (PM) probes and a large amount of weaker cross-hybridization signals from mismatching (MM) probes. The latter are crucial in the data analysis. Seven coded clinical samples (HIV-1) are analyzed, and the microarray results are in full concordance with Sanger sequencing data. Moreover, the thermodynamic analysis of microarray signals resolves inherent ambiguities in Sanger data of mixed samples and provides additional clinically relevant information. These results show the reliability and added value of DNA microarrays for point-of-care diagnostic purposes.     

Whole-organism studies of adhesion in pad-bearing lizards: creative evolutionary solutions to functional problems

Understanding the evolution of complex functional traits is a challenge for evolutionary physiology. Here we investigate the evolution of subdigital toepads in lizards, which have arisen independently at least three times, although with subtle anatomical differences. Some designs (anole, gecko) appear functionally equivalent, whereas other designs (skink) are inferior. The functional equivalence of geckos and anoles highlights the creative aspect of the evolutionary process in that these two groups have arrived at the same functional endpoint along very different trajectories. However, this functional equivalence does not result in equivalence for performance at whole-organism tasks (e.g., running uphill), as the evolution of behavior (e.g., toe-furling) has enabled geckos to be superior climbers than anoles. We also show that adaptive increases in the toepad size within a closely related lizard genus (Anolis) has resulted in concomitant evolution of enhanced clinging ability and increased perch heights. A third insight is that pad-bearing geckos are capable of carrying tremendous loads (up to 250% of body weight) up smooth surfaces, and that the toepad itself does not appear limiting. This comparative and whole-organism approach to lizard toepads underscores how organisms can evolve multiple solutions to evolutionary problems.     

Lignification and cell wall thickening in nodes of Phyllostachys viridiglaucescens and Phyllostachys nigra

BACKGROUND AND AIMS: Bamboos are among the most important plants in the world. The anatomical structure and mechanical properties of the culm internode are well documented. Fewer details are available of the culm node. The aim of this study was a topochemical investigation on lignification and cell wall thickening in developing and maturing bamboo nodes. The deposition sequence and distribution of lignin structural units and cell wall thickening in different anatomical regions of the node of Phyllostachys viridiglaucescens and Phyllostachys nigra are discussed. METHODS: Cell wall thickening and lignification are investigated in the outer part of the nodal region and in the diaphragm of developing and maturing P. nigra culms and in maturing culms of P. viridiglaucescens of different age classes. The lignification during ageing was studied topochemically by means of cellular UV microspectrophotometry. A combination of light microscopy and image analysis techniques were used to measure cell wall thickness. KEY RESULTS: The fibre and parenchyma cell wall thickness does not significantly increase during ageing. In the diaphragm, the cell walls are thinner and the cell diameter is larger than in the outer part of the node. In shoots, the lignin content in the epidermis, hypodermis and in both fibre and parenchyma cells of the diaphragm is relatively low compared with older culms. The fibre and parenchyma cells of the diaphragm have higher values of p-coumaric and ferulic acids than fibre and parenchyma cells of the outer part of the node. CONCLUSIONS: It was hypothesized that the combination of more hydroxycinnamic acids and of thinner cell walls in combination with higher cell diameters (lower density and lower stiffness) in the diaphragm than in the outer part of the node may play an important role in the biomechanical function of the node by acting as a spring-like joint to support the culm by bending forces.     

Is phylogeny driving tendon length in lizards?

Tulli, M.J., Herrel, A., Vanhooydonck, B. and Abdala, V. 2012. Is phylogeny driving tendon length in lizards?—Acta Zoologica (Stockholm) 93 : 319–329. Tendons transmit tensile forces generated by muscles and are a crucial part of the musculoskeletal system in vertebrates. Because tendons and tendon cells respond to altered mechanical load by increasing collagen synthesis, we hypothesized that a correlation between tendon morphology and the loading regime imposed by locomotor style or habitat use exists. This makes tendons an interesting model for studying the relationship between morphology and environment. In this study, we compare the general morphology of the palmar flexor plate, the length of the digital tendons, and the length of the flexor carpi ulnaris tendon in species of lizards that exploit a variety of structural habitats. The results from statistical analyses show that phylogenetic relatedness has a major impact on our ability to detect differences between habitat groups, and no differences in tendon length could be detected between iguanian species occupying different habitats when taking into account the relatedness between species. Our data for lizards diverge from the general mammalian paradigm where variation in tendon is often associated with habitat use or locomotor style.