Compensatory density feedback of Oncomelania hupensis populations in two different environmental settings in China

BACKGROUND: The most recent strategy for schistosomiasis control in the People's Republic of China aims to reduce the likelihood of environmental contamination of schistosome eggs. Despite considerable progress, it is believed that achievements would be further consolidated with additional intermediate host snail control measures. We provide an empirical framework for discerning the relative contribution of intrinsic effects (density feedback) from other extrinsic drivers of snail population dynamics. METHODS: We set up experiments in two study locations to collect reproduction data of Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum. We applied a set of four population dynamic models that have been widely used to study phenomenological time-series data to examine the properties of demographic density feedback patterns from abundance data. We also contrasted the obtained results with the component feedback of density on survival rate to determine whether adult survival was the principal driver of the demographic feedback observed. RESULTS: Demographic density feedback models (Ricker- and Gompertz-logistic) accounted for <99% of Akaike's information criterion model weight, with the Gompertz ranking highest in all O. hupensis population groups. We found some evidence for stronger compensatory feedback in the O. hupensis population from Sichuan compared to a Jiangsu population. Survival rates revealed strong component feedback, but the log-linear relationships (i.e. Gompertz) had less support in the demographic feedback analysis. CONCLUSIONS: Our findings indicate that integrated schistosomiasis control measures must continue to reduce parasite abundance further because intermediate host snail populations tend to grow exponentially at low densities, especially O. hupensis populations in mountainous regions. We conclude that density feedback in adult survival is the principal component contribution to the demographic phenomenon observed in the population fitness (r)-abundance relationship

ALMA ACA and Nobeyama Observations of Two Orion Cores in Deuterated Molecular Lines

We mapped two molecular cloud cores in the Orion A cloud with the 7 m Array of the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeterArray (ALMA) and with the Nobeyama 45 m radio telescope. These cores have bright N2D+ emission in single-pointing observations with the Nobeyama 45 m radio telescope, have a relatively high deuterium fraction, and are thought to be close to the onset of star formation. One is a star-forming core, and the other is starless. These cores are located along filaments observed in N2H+ and show narrow line widths of 0.41 km s−1 and 0.45 km s−1 in N2D+, respectively, with the Nobeyama 45 m telescope. Both cores were detected with the ALMA ACA 7 m Array in the continuum and molecular lines at Band 6. The starless core G211 shows a clumpy structure with several sub-cores, which in turn show chemical differences. Also, the sub-cores in G211 have internal motions that are almost purely thermal. The starless sub-core G211D, in particular, shows a hint of the inverse P Cygni profile, suggesting infall motion. The star-forming core G210 shows an interesting spatial feature of two N2D+ peaks of similar intensity and radial velocity located symmetrically with respect to the single dust continuum peak. One interpretation is that the two N2D+ peaks represent an edge-on pseudo-disk. The CO outflow lobes, however, are not directed perpendicular to the line connecting both N2D+ peaks