Resolving the first steps to multicellularity

Multicellular life has evolved many times, yet each origin requires free cells to integrate unselfishly into a higher-level individual. How can such transitions evolve? In a new paper, Herron and Michod investigate the recent origins of multicellularity in colonial algae. Their phylogenetic reconstructions provide a striking dissection of early steps, and altruistic traits are at the crux of it. Key evolutionary reversals are also revealed, where cellular selfishness might have thwarted multicellular integration.     

Alpha cells take off first

Using a transgenic mouse line in which GFP is expressed in a single population of retinal ganglion cells (RGCs), Huberman and colleagues report in this issue of Neuron that the axon terminals of RGCs exhibit an orderly pattern of distribution in the higher visual centers. This pattern undergoes a developmental refinement, and synchronous activity in the retina regulates columnar but not laminar formation.     

Moving in the real world: tortoises take the plunge to cross steep steps

Despite exhibiting low velocity and limited agility, many tortoises undertake large scale movements and must overcome various obstacles, notably in populations living in hilly or rocky habitats. Although crucial, studies exploring how tortoises move in complex and irregular environments are scarce. In this context, we examined an important behavioural trait: how tortoises (Testudo hermanni) deal with step‐like obstacles. In their natural habitat, individuals were positioned in a challenging situation: they were placed on a bench approximately 50 cm high, and were observed over a 10‐min period. We compared the behaviour of the tortoises (taking a risk to ‘jump’ or waiting) from two populations living in contrasted habitats: flat versus rugged (crisscrossed by cliffs and rocky steps). Individuals from the flat habitat were reluctant to jump, whereas most tortoises from the rugged habitat jumped. Immature tortoises were less willing to jump compared to larger and more experienced adults. These results suggest that challenging habitats increase boldness. In addition to fundamental findings, these results may have conservation value and assist in improving translocation strategies for endangered tortoise populations. © 2013 The Linnean Society of London     

Genetic knockout--the first steps and outlook for a neurophysiology of behavior

A review of modern data on genetic knockout strategy application to study the brain neurotransmitters and their role in the regulation of behavior. Advantages and shortcomings of genetic knockout of receptors and the enzymes of neurotransmitters metabolism models in comparison to other methods are discussed. Data on the effect of genetic knockout of various types of opioid, dopamine, serotonin and adrenoreceptors as well as enzymes in biosynthesis of catecholamines and serotonin on physiology and behavior is adduced. The data provide evidence that genetic knockout reproduces a principal effects of the lack of receptors and enzymes and allows to find new yet unknown properties. Mouse strains with genetic knockout represent unique models of hereditary neuropathology. At the same time the data presented clearly demonstrated that the lack of a single type of receptor or enzyme does not lead usually to disorganization of regulated by them physiological functions and behavior. The data witness to the complexity and multifactoriality of their regulations and evidenced the great compensatory potentials of organism.     

The first steps in Drosophila motion detection

The visual system, with its ability to perceive motion, is crucial for most animals to walk or fly steadily. Theoretical models of motion detection exist, but the underlying cellular mechanisms are still poorly understood. In this issue of Neuron, Rister and colleagues dissect the function of neuronal subtypes in the optic lobe of Drosophila to reveal their role in motion detection.