Small queens and big-headed workers in a monomorphic ponerine ant

Evolution of caste is a central issue in the biology of social insects. Comparative studies on their morphology so far suggest the following three patterns: (1) a positive correlation between queen–worker size dimorphism and the divergence in reproductive ability between castes, (2) a negative correlation among workers between morphological diversity and reproductive ability, and (3) a positive correlation between queen–worker body shape difference and the diversity in worker morphology. We conducted morphological comparisons between castes in Pachycondyla luteipes, workers of which are monomorphic and lack their reproductive ability. Although the size distribution broadly overlapped, mean head width, head length, and scape length were significantly different between queens and workers. Conversely, in eye length, petiole width, and Weber’s length, the size differences were reversed. The allometries (head length/head width, scape length/head width, and Weber’s length/head width) were also significantly different between queens and workers. Morphological examinations showed that the body shape was different between queens and workers, and the head part of workers was disproportionately larger than that of queens. This pattern of queen–worker dimorphism is novel in ants with monomorphic workers and a clear exception to the last pattern. This study suggests that it is possible that the loss of individual-level selection, the lack of reproductive ability, influences morphological modification in ants.     

Seasonal change of persistent organic pollutant concentrations in air at Niigata area,Japan

The concentrations of persistent organic pollutants (POPs), such as HCB, alpha-, beta-, gamma- and delta-HCH, trans- and cis-chlordane (t-CHL, c-CHL), DDE, DDD and DDT, in ambient air have been measured at five sampling points in Niigata area, Japan (Niigata, Maki, Tsubame, Jouzo and Yahiko) during the period from September 1999 to November 2001. HCB, alpha-HCH, t-CHL and c-CHL showed higher concentrations than the other chemicals in all locations. All the POPs except t-CHL and c-CHL collected at urban sites of the Niigata Plain was almost the same in their concentration levels. Higher concentrations of t-CHL and c-CHL in residential areas should be attributed to the past usage of the chemical as a termiticide. At Yahiko (remote site), most of the POPs showed lower concentrations than those measured at the other sampling sites, although alpha-HCH and gamma-HCH were comparable with the concentrations found at the other sampling sites. All POPs except alpha-HCH and gamma-HCH tend to decrease 41-80% in their concentrations from 2000 to 2001. The lower POPs concentrations in winter and the higher POPs concentrations in summer at every sampling point can be partly explained by temperature differences. Applying the equation of the logarithm of the POP partial pressure in air versus reciprocal temperature (lnPa=m/T+b) to our data, linear relations were observed. HCB gave a poor linearity and the smallest slope, while beta-HCH, t-CHL and c-CHL gave good linearities and large slopes in the equation. The results suggest that HCB level is influenced by not only the emission from terrestrial sources but the global-scale background pollution. A peculiar observation is that beta-HCH concentration measured in our study showed large temperature dependence, indicating there could be a source of contamination in the surrounding areas.     

Peak wind speed modulation by large-scale motions in neutrally stratified atmospheric surface layer

Environmental Fluid Mechanics - This study applies the models describing the effect of a neutrally stratified high-Reynolds-number boundary layer on peak wind estimation. A neutrally stratified...