Form-function relationships underlie rapid dietary changes in a lizard.

Macroevolutionary changes such as variation in habitat use or diet are often associated with convergent, adaptive changes in morphology. However, it is still unclear how small-scale morphological variation at the population level can drive shifts in ecology such as observed at a macroevolutionary scale. Here, we address this question by investigating how variation in cranial form and feeding mechanics relate to rapid changes in diet in an insular lizard (Podarcis siculus) after experimental introduction into a new environment. We first quantified differences in the skull shape and jaw muscle architecture between the source and introduced population using three-dimensional geometric morphometrics and dissections. Next, we tested the impact of the observed variation in morphology on the mechanical performance of the masticatory system using computer-based biomechanical simulation techniques. Our results show that small differences in shape, combined with variation in muscle architecture, can result in significant differences in performance allowing access to novel trophic resources. The confrontation of these data with the already described macroevolutionary relationships between cranial form and function in these insular lizards provides insights into how selection can, over relatively short time scales, drive major changes in ecology through its impact on mechanical performance.

Getting a grip on the evolution of grasping in musteloid carnivorans: a three-dimensional analysis of forelimb shape.

The ability to grasp and manipulate is often considered a hallmark of hominins and associated with the evolution of their bipedal locomotion and tool use. Yet, many other mammals use their forelimbs to grasp and manipulate objects. Previous investigations have suggested that grasping may be derived from digging behaviour, arboreal locomotion or hunting behaviour. Here, we test the arboreal origin of grasping and investigate whether an arboreal lifestyle could confer a greater grasping ability in musteloid carnivorans. Moreover, we investigate the morphological adaptations related to grasping and the differences between arboreal species with different grasping abilities. We predict that if grasping is derived from an arboreal lifestyle, then the anatomical specializations of the forelimb for arboreality must be similar to those involved in grasping. We further predict that arboreal species with a well-developed manipulation ability will have articulations that facilitate radio-ulnar rotation. We use ancestral character state reconstructions of lifestyle and grasping ability to understand the evolution of both traits. Finally, we use a surface sliding semi-landmark approach capable of quantifying the articulations in their full complexity. Our results largely confirm our predictions, demonstrating that musteloids with greater grasping skills differ markedly from others in the shape of their forelimb bones. These analyses further suggest that the evolution of an arboreal lifestyle likely preceded the development of enhanced grasping ability.

A Practical Guide to Sliding and Surface Semilandmarks in Morphometric Analyses.

Advances in imaging technologies, such as computed tomography (CT) and surface scanning, have facilitated the rapid generation of large datasets of high-resolution three-dimensional (3D) specimen reconstructions in recent years. The wealth of phenotypic information available from these datasets has the potential to inform our understanding of morphological variation and evolution. However, the ever-increasing ease of compiling 3D datasets has created an urgent need for sophisticated methods of capturing high-density shape data that reflect the biological complexity in form. Landmarks often do not take full advantage of the rich shape information available from high-resolution 3D specimen reconstructions, as they are typically restricted to sutures or processes that can be reliably identified across specimens and exclude most of the surface morphology. The development of sliding and surface semilandmark techniques has greatly enhanced the quantification of shape, but their application to diverse datasets can be challenging, especially when dealing with the variable absence of some regions within a structure. Using comprehensive 3D datasets of crania that span the entire clades of birds, squamates and caecilians, we demonstrate methods for capturing morphology across incredibly diverse shapes. We detail many of the difficulties associated with applying semilandmarks to comparable regions across highly disparate structures, and provide solutions to some of these challenges, while considering the consequences of decisions one makes in applying these approaches. Finally, we analyze the benefits of high-density sliding semilandmark approaches over landmark-only studies for capturing shape across diverse organisms and discuss the promise of these approaches for the study of organismal form.

Um guia prático para demarcação de semi pontos de referência de superfície e de deslizamento em análises morfométricas Os avanços nas tecnologias de imagem, como a tomografia computadorizada (CT) e a varredura de superfície, facilitaram a rápida geração de grandes conjuntos de dados de reconstruções de espécimes 3D de alta resolução nos últimos anos. A riqueza de informações fenotípicas disponíveis nesses conjuntos de dados tem o potencial de informar nossa compreensão da variação e evolução morfológica. No entanto, a facilidade cada vez maior de compilar conjuntos de dados 3D criou uma necessidade urgente de métodos sofisticados para a captura de dados de alta densidade que reflitam a complexidade biológica na forma. Os pontos de referência morfológicos geralmente não capturam o máximo das informações sobre a morfologia disponíveis nas reconstruções de espécimes 3D em alta resolução, pois normalmente são restritas a suturas ou processos que podem ser identificados de forma confiável em diferentes espécimes, excluindo a maior parte da morfologia de superfície. O desenvolvimento de técnicas de deslizamento e de semi pontos de referência de superfíce melhorou muito a quantificação da forma, mas sua aplicação a diversos conjuntos de dados pode ser um desafio, especialmente quando algumas regiões dentro de uma estrutura são ausentes. Usando conjuntos de dados tridimensionais abrangentes do crânio, abrangendo todos os clados de pássaros, lagartos Squamata e cecílias, nós demonstramos métodos para captura da morfologia em formas incrivelmente diversas. Nós detalhamos muitas das dificuldades associadas à aplicação de semi pontos de referência em regiões comparáveis de estruturas altamente díspares, e fornecemos soluções para alguns desses desafios, enquanto consideramos as consequências das decisões tomadas na aplicação dessas abordagens. Finalmente, analisamos os benefícios das abordagens de deslizamento do semi pontos de referência em alta densidade para capturar a forma em diversos organismos e discutir a promessa dessas abordagens para o estudo da forma do organismo. Translated to Portuguese by Diego Vaz (dbistonvaz@vims.edu).

Cell surface adenylate kinase activity regulates the F(1)-ATPase/P2Y (13)-mediated HDL endocytosis pathway on human hepatocytes.

We have previously demonstrated on human hepatocytes that apolipoprotein A-I binding to an ecto-F(1)-ATPase stimulates the production of extracellular ADP that activates a P2Y(13)-mediated high-density lipoprotein (HDL) endocytosis pathway. Therefore, we investigated the mechanisms controlling the extracellular ATP/ADP level in hepatic cell lines and primary cultures to determine their impact on HDL endocytosis. Here we show that addition of ADP to the cell culture medium induced extracellular ATP production that was due to adenylate kinase [see text] and nucleoside diphosphokinase [see text] activities, but not to ATP synthase activity. We further observed that in vitro modulation of both ecto-NDPK and AK activities could regulate the ADP-dependent HDL endocytosis. But interestingly, only AK appeared to naturally participate in the pathway by consuming the ADP generated by the ecto-F(1)-ATPase. Thus controlling the extracellular ADP level is a potential target for reverse cholesterol transport regulation.