Acetaldehyde: a low-concentration resource and larval attractant in 3Drosophila species

Summary Acetaldehyde is used as an energy source and attracts larvae up to low concentrations where it becomes a stress and a larval repellant, inD. melanogaster, D. simulans, andD. immigrans. This result is expected, since acetaldehyde is an intermediary compound between ethanol and acetic acid, both of which are utilized as resources and attract larvae to varying thresholds according to species and genotype.We thank Jan Clarke for assistance, and the Australian Research Grants Committee for partial financial support.     

A new gamma-ray burst classification scheme from GRB 060614

Gamma-ray bursts (GRBs) are known to come in two duration classes, separated at approximately 2 s. Long-duration bursts originate from star-forming regions in galaxies, have accompanying supernovae when these are near enough to observe and are probably caused by massive-star collapsars. Recent observations show that short-duration bursts originate in regions within their host galaxies that have lower star-formation rates, consistent with binary neutron star or neutron star-black hole mergers. Moreover, although their hosts are predominantly nearby galaxies, no supernovae have been so far associated with short-duration GRBs. Here we report that the bright, nearby GRB 060614 does not fit into either class. Its approximately 102-s duration groups it with long-duration GRBs, while its temporal lag and peak luminosity fall entirely within the short-duration GRB subclass. Moreover, very deep optical observations exclude an accompanying supernova, similar to short-duration GRBs. This combination of a long-duration event without an accompanying supernova poses a challenge to both the collapsar and the merging-neutron-star interpretations and opens the door to a new GRB classification scheme that straddles both long- and short-duration bursts.