New and Exciting in PLoS

Plant Classification from Bat-Like Echolocation Signals:

Bats are able to classify plants using echolocation. They emit ultrasonic signals and can recognize the plant according to the echo returning from it. This ability assists them in many of their daily activities, like finding food sources associated with certain plants or using landmarks for navigation or homing. The echoes created by plants are highly complex signals, combining together all the reflections from the many leaves that a plant contains. Classifying plants or other complex objects is therefore considered a troublesome task and we are far from understanding how bats do it. In this work, we suggest a simple algorithm for classifying plants according to their echoes. Our algorithm is able to classify with high accuracy plant echoes created by a sonar head that simulates a typical frequency-modulated bat's emitting receiving parameters. Our results suggest that plant classification might be easier than formerly considered. It gives us some hints as to which features might be most suitable for the bats, and it opens possibilities for future behavioral experiments to compare its performance with that of the bats.

Evolution of a Core Gene Network for Skeletogenesis in Chordates:

Important molecular mechanisms underlying mammalian skeletogenesis have been described but knowledge about the evolutionary origin of these gene networks is limited. The Runt gene family (Runx1-3) is of extraordinary importance for skeletogenesis. Runx2 deficient mice completely lack bone. Runx2 and Runx3 are essential for cartilage development and Runx2 regulates the key factor Indian hedgehog, which coordinates skeletogenesis. Here, we reconstructed Runt gene evolution in correlation to skeletal evolution. By analyzing lancelets, one of the closest living relatives of vertebrates, we revealed that the single Runt and Hedgehog family founder genes were co-expressed in primitive skeletal elements of the chordate stem species. Interestingly, at this stage the Runt and Hedgehog pathways were already directly linked to one another. Furthermore we isolated two Runt genes from a representative of jawless cartilaginous fish (hagfish) and three Runt genes from jawed cartilaginous fish (dogfish) which were all expressed in cartilage. The dogfish Runt genes were also found in teeth and placoid scales. This study suggests that Runt genes were involved in all ancient processes of chordate skeletogenesis. Furthermore the analysis supports the theory that most likely the gut was the tissue that originally secreted an acellular gill gut skeleton in the chordate ancestor.