• Letter |

    It has long been thought that motor control is achieved through the balanced activity of two distinct pathways through the basal ganglia that have opposing effects, but this has never been functionally verified. These authors directly test this hypothesis with optogenetic activation of different populations of mouse striatal neurons, and not only trace functional connectivity but demonstrate opposing effects on motor behaviour in a parkinsonian model.

    • Alexxai V. Kravitz
    • , Benjamin S. Freeze
    •  & Anatol C. Kreitzer
  • Letter |

    Although pheromones and their detection by the vomeronasal organ are known to govern social behaviour in mice, specific chemical signals have rarely been linked to selective behavioural responses. Here the authors show that the ESP1 peptide secreted in male tears makes females sexually receptive, and identify its specific vomeronasal receptor and the sex-specific neuronal circuits activated during the behavioural response.

    • Sachiko Haga
    • , Tatsuya Hattori
    •  & Kazushige Touhara
  • Letter |

    Plants or animals with identical genomes in a given species can develop into wildly differing forms, depending on environmental conditions, a phenomenon that is widespread in nature yet rarely described in genetic and molecular terms. These authors show that the formation of additional teeth-like structures in the mouth of the nematode Pristionchus pacificus in response to overcrowding is mediated by the same endocrine system that controls dauer larva formation.

    • Gilberto Bento
    • , Akira Ogawa
    •  & Ralf J. Sommer
  • Letter |

    The European corn borer consists of two sex pheromone races, leading to strong reproductive isolation which could represent a first step in speciation. Female sex pheromone production and male behavioural response are under the control of different genes, but the identity of these genes is unknown. These authors show that allelic variation in a gene essential for pheromone biosynthesis accounts for the phenotypic variation in female pheromone production, leading to race-specific signals.

    • Jean-Marc Lassance
    • , Astrid T. Groot
    •  & Christer Löfstedt
  • Letter |

    One of the steps in the evolution of tetrapod limbs was the loss of the distinctive fringe of fin rays and fin folds found in the fins of fishes. It is now shown that two novel proteins, actinodin 1 and 2, are essential structural components of fin rays and fin folds in zebrafish, and are also encoded in the genomes of other teleost fish and at least one species of shark, but not in tetrapods. It is suggested that the loss of these genes may have contributed to the fin-to-limb transition in tetrapod evolution.

    • Jing Zhang
    • , Purva Wagh
    •  & Marie-Andrée Akimenko
  • Letter |

    What is the best way for predators to find food when prey is sparse and distributed unpredictably? Theory predicts that in such circumstances predators should adopt a Lé-flight strategy, in which short exploratory hops are occasionally interspersed with longer trips. When prey is abundant, simple Brownian motion should suffice. Now, analysis of a large data set of marine predators establishes that animals do indeed adopt Lévy-flight foraging when prey is sparse, and Brownian episodes when prey is abundant.

    • Nicolas E. Humphries
    • , Nuno Queiroz
    •  & David W. Sims
  • Letter |

    The 505-million-year-old Burgess Shales of British Columbia are justifiably famous for the exquisite preservation of their fossils, and for the extreme oddity of many of them. One such is Nectocaris pteryx, which, from the few fossils available for study, looked like a chordate fused with an arthropod. However, the collection and examination of more fossils of Nectocaris suggests that it in fact represents an early offshoot of cephalopod molluscs — a kind of squid, though with two rather than eight or ten tentacles.

    • Martin R. Smith
    •  & Jean-Bernard Caron
  • Letter |

    The Burgess Shales of British Columbia are famous for having yielded fossils of soft-bodied creatures from the Middle Cambrian period. Although similar faunas are now known from localities as far apart as China and Greenland, they seem to have died out before the end of the Cambrian. Or did they? Here, the discovery of a Burgess Shale-type fauna from the Ordovician period in Morocco is reported, showing that creatures of this type persisted beyond the end of the Cambrian.

    • Peter Van Roy
    • , Patrick J. Orr
    •  & Derek E. G. Briggs
  • Letter |

    What agents of selection shape creatures in the wild? The answer for the brown anole lizard seems to be competition with its fellows, rather than predation from without. Bird or snake predators were included or excluded across six Caribbean islands that ranged from low to high population densities of lizards. Although the presence of predators altered lizard behaviour, it was increases in lizard population density that altered the lizard's phenotype, favouring larger size, longer legs and increased stamina for running.

    • Ryan Calsbeek
    •  & Robert M. Cox
  • Letter |

    How large groups of animals move in a coordinated way has defied complete explanation. Inability to track each member of a flock has hampered understanding of the behavioural rules governing flocks of birds. This, however, has been achieved for a small group of homing pigeons fitted with lightweight GPS loggers. A well–defined hierarchy is revealed — the average position of a pigeon within the flock strongly correlates with is position in the social hierarchy (a kind of airborne pecking order).

    • Máté Nagy
    • , Zsuzsa Ákos
    •  & Tamás Vicsek
  • Letter |

    It is generally accepted that specific neuronal circuits in the brain's cortex drive behavioural execution, but the relationship between the performance of a task and the function of a circuit is unknown. Here, this problem was tackled by using a technique that allows many neurons within the same circuit to be monitored simultaneously. The findings indicate that enhanced correlated activity in specific ensembles of neurons can identify and encode specific behavioural responses while a task is learned.

    • Takaki Komiyama
    • , Takashi R. Sato
    •  & Karel Svoboda
  • Letter |

    Study of two specimens of the feathered dinosaur Similicaudipteryx shows that the morphology of dinosaur feathers changed dramatically as the animals matured. Moreover, the morphology of feathers in dinosaurs was much more varied than one would expect from looking at feathers in modern birds.

    • Xing Xu
    • , Xiaoting Zheng
    •  & Hailu You
  • Letter
    | Open Access

    The genome of the zebra finch — a songbird and a model for studying the vertebrate brain, behaviour and evolution — has been sequenced. Comparison with the chicken genome, the only other bird genome available, shows that genes that have neural function and are implicated in the cognitive processing of song have been evolving rapidly in the finch lineage. Moreover, vocal communication engages much of the transcriptome of the zebra finch brain.

    • Wesley C. Warren
    • , David F. Clayton
    •  & Richard K. Wilson
  • Letter |

    Although humans have engaged in long-distance running either barefoot or with minimal footwear for most of human evolutionary history, the modern running shoe was not invented until the 1970s. Here, runners who habitually run in sports shoes are shown to run differently to those who habitually run barefoot, with the latter often landing on the fore-foot rather than the rear-foot. This strike pattern may have evolved to protect from some of the impact-related injuries now experienced by runners.

    • Daniel E. Lieberman
    • , Madhusudhan Venkadesan
    •  & Yannis Pitsiladis
  • Letter |

    Echolocation is usually associated with bats. Many echolocating bats produce signals in the larynx, but a few species produce tongue clicks. Here, studies show that in all bats that use larynx-generated clicks, the stylohyal bone is connected to the tympanic bone. Study of the stylohyal and tympanic bones of a primitive fossil bat indicates that this species may have been able to echolocate, despite previous evidence to the contrary, raising the question of when and how echolocation evolved in bats.

    • Nina Veselka
    • , David D. McErlain
    •  & M. Brock Fenton
  • Letter |

    Animals use the Earth's magnetic field for orientation but the biophysical basis of this is unclear. The light-dependent magnetic sense of Drosophila melanogaster was recently shown to be mediated by the cryptochrome (Cry) photoreceptor; here, using a transgenic approach, the type 1 and 2 Cry of the monarch butterfly are shown to both function in the magnetoreception system of Drosophila, and probably use an unconventional photochemical mechanism.

    • Robert J. Gegear
    • , Lauren E. Foley
    •  & Steven M. Reppert