A simple dynamic model explains the diversity of island birds worldwide

International audienc

Mechanics of Arboreal Locomotion in Swinhoe’s Striped Squirrels: A Potential Model for Early Euarchontoglires

Differences between arboreal and terrestrial supports likely pose less contrasting functional demands on the locomotor system at a small body size. For arboreal mammals of small body size, asymmetrical gaits have been demonstrated to be advantageous to increase dynamic stability. Many of the extant arboreal squirrel-related rodents display a small body size, claws on all digits, and limited prehensility, a combination that was proposed to have characterized the earliest Euarchontoglires. Thus, motion analysis of such a modern analog could shed light onto the early locomotor evolution of eurarchontoglirans. In this study, we investigated how Swinhoe’s striped squirrels (Tamiops swinhoei; Scuiromorpha) adjust their locomotion when faced with different orientations on broad supports and simulated small branches. We simultaneously recorded high-Hz videos (501 trials) and support reaction forces (451 trials) of squirrels running on two types of instrumented trackways installed at either a 45° incline (we recorded locomotion on inclines and declines) or with a horizontal orientation. The striped squirrels almost exclusively used asymmetrical gaits with a preference for full bounds. Locomotion on simulated branches did not differ substantially from locomotion on the flat trackway. We interpreted several of the quantified adjustments on declines and inclines (in comparison to horizontal supports) as mechanisms to increase stability (e.g., by minimizing toppling moments) and as adjustments to the differential loading of fore- and hind limbs on inclined supports. Our data, in addition to published comparative data and similarities to the locomotion of other small arboreal rodents, tree shrews, and primates as well as a likely small body size at the crown-group node of Euarchontoglires, render a preference for asymmetrical gaits in early members of the clade plausible. This contributes to our understanding of the ancestral lifestyle of this mammalian ‘superclade’.Peer Reviewe

Is there a size-dependency in the predator- prey interaction of Asterias rubens and Mytilus edulis?

This study examines the complex structure of prey and predator interactions, which are regulated by a variety of factors. Here, we are focusing on the prey size preference of the starfish Asterias rubens and its prey, the bivalve Mytilus edulis and its dependency on the size of the predator. Both species co-occur in the Wadden Sea of Sylt, Germany, where our experiment took place. In the course of this study we found that individuals of Asterias rubens favor mid-sized individuals of Mytilus edulis independently of their own size. Furthermore, our study revealed that medium-sized sea stars show the highest amount of activity in general.Diese Studie untersucht die komplexe Struktur von Beute- und Räuberinteraktionen, die durch eine Vielzahl von Faktoren reguliert werden. Hier konzentrieren wir uns auf die Beutegrößenpräferenz des Seesterns Asterias rubens und seiner Beute, der Muschel Mytilus edulis und deren Abhängigkeit von der Größe des Räubers. Beide Arten kommen gemeinsam im Wattenmeer von Sylt vor, wo unser Experiment stattfand. Im Rahmen dieser Studie fanden wir heraus, dass Individuen von Asterias rubens unabhängig von ihrer eigenen Größe mittelgroße Individuen von Mytilus edulis bevorzugen. Darüber hinaus zeigte unsere Studie, dass mittelgroße Seesterne im Allgemeinen die höchste Aktivität aufweisen.Peer Reviewe

EXPLORING SPONGE-INHABITING BARNACLES OF EASTERN INDONESIA USING MICRO-CT SCANNING

We present a morphological study of Indonesian sponge-inhabiting barnacles using standard light microscopy in combination with micro-CT scanning and computer-aided 3D-reconstruction of the external shell morphology. A taxonomic analysis of the material detected four different genera of sponges inhabited by five different species of balanomorph barnacles, two of which are undescribed. Together with conventional morphological examination by dissection, we provide modern non-destructive imaging methods, using micro-CT scanning to enhance our knowledge of the morphological characters of sponge-inhabiting barnacles from eastern Indonesia. Although there were some methodological limitations regarding the contrast-enhancing technique, this study demonstrates micro-CT as a useful non-destructive technique of integrative taxonomy, for the examination of sponge-inhabiting barnacles.

Proceedings in Marine Biology

“Proceedings in Marine Biology” is an international journal publishing original research by graduate students on all aspects of marine biology. Subjects covered include: ecological surveys and population studies of oceanic, coastal and shore communities; physiology and experimental biology; taxonomy, morphology and life history of marine animals and plants. Papers are also published on techniques em- ployed at sea for sampling, recording, capture and observation of marine organisms.Zeitschrift zur Kursabschlussreise der Humboldt-Universität zu Berlin (Deutschland) im Bereich Elektronenmikroskopie.Peer Reviewe