Antagonistic interactions between the african weaver ant Oecophylla longinoda and the parasitoid Anagyrus pseudococci potentially limits suppression of the invasive mealybug Rastrococcus iceryoides

The ant Oecophylla longinoda Latreille forms a trophobiotic relationship with the invasive mealybug Rastrococus iceryoides Green and promotes the latter's infestations to unacceptable levels in the presence of their natural enemies. In this regard, the antagonistic interactions between the ant and the parasitoid Anagyrus pseudococci Girault were assessed under laboratory conditions. The percentage of parasitism of R. iceryoides by A. pseudococci was significantly higher on "ant-excluded" treatments (86.6% ± 1.27%) compared to "ant-tended" treatments (51.4% ± 4.13%). The low female-biased sex-ratio observed in the "ant-tended" treatment can be attributed to ants' interference during the oviposition phase, which disrupted parasitoids' ability to fertilize eggs. The mean foraging time, host handling time and number of successful oviposition in "ant-excluded" treatment were significantly higher compared to "ant-tended" treatments. When ant workers were allowed access to sterilized sand grains, mummified and unmummified R. iceryoides, they selectively removed the mummified mealybugs, indicating that they recognized the mummies as potential foods (1.2 ± 0.46 to 7.8 ± 1.17 mummies at 10 min intervals for 2 h). Percentage emergence from mummified R. iceryoides removed by the ants was significantly lower compared to emergence from mummies not exposed to ants. Although, host seeking parasitoids frequently evaded attacks, some were killed by the foraging ant workers (2.0 ± 0.38 to 6.0 ± 0.88 at 10 min intervals for 2 h). These results suggest for the first time that the presence of O. longinoda has a detrimental effect on the abundance, reproductive success and possibly oviposition strategy of female parasitoids, which might be a delimiting factor in field conditions if both natural enemies are to be recommended for use within the same agro-ecosystem.

Dissolved chemical elements in river waters of the Wrangel Island

Pioneer information about chemical composition of river waters in the Wrangel Island has been obtained. It is shown that water composition reflects the lithogeochemical specifics of primary rocks and ore mineralization. In contrast to many areas of the Russian Far North river waters of the island are characterized by elevated background value of total mineralization (i.e., total dissolved solids, TDS) (0.3-2 g/l) and specific chemical type (SO4-Ca-Mg). This is related to abundance of Late Carboniferous gypsiferous and dolomitic sequences in the mountainous area of the island. It has also been established that salt composition of some streams is appreciably governed by supergene alterations of sulfide mineralization associated with quartz-carbonate vein systems. They make up natural centers of surface water contamination. Waters in such streams are characterized by low pH values (2.4-5.5), high TDS (up to 6-23 g/l) and SO4-Mg composition. These waters are also marked by anomalously high concentrations of heavy and non-ferrous metals, as well as REE, U, and Th.