Host preference of a symbiotic flatworm in relation to the ecology of littoral snails

Some polyclads associate with other marine invertebrates such as gastropods, but how these associations evolve is not well understood. This study examined the relationships between a polyclad, Stylochoplana pusilla, and six species of snails in 10 eulittoral sites in Mutsu Bay, northern Japan, in 2010 and 2011. Of the six potential host snail species, Monodonta labio was present at all sites and the prevalence of S. pusilla in the snails’ mantle cavities overall was 82.6 %. Four other snail species occurred at five or six sites in comparable densities, but of these, only Chlorostoma turbinatum and Omphalius rusticus had S. pusilla in their mantle cavities (prevalence of 42.0 and 15.4 %). A congener of M. labio, Monodonta neritoides, occurred at only one site and had no S. pusilla. The mantle, which provides habitat space for S. pusilla, was proportionally the longest in M. labio. In laboratory experiments, the flatworms preferentially entered M. labio over other snail species with the same mantle length. Observed vertical distributions of snails in the littoral zone indicate that M. labio is present in the eulittoral at both high and low tides, while C. turbinatum and O. rusticus are usually found in the sublittoral. In an evolutionary sense, the relationship between S. pusilla and its host may have developed as a mechanism for the flatworm to avoid predation by living in the eulittoral and to avoid desiccation by establishing commensal relationships with certain snails.     

脉冲放电法消除汞蒸气的实验研究

利用窄脉冲电方法来消除垃圾焚烧炉烟气中的汞蒸气，并进行了１０ｍ＾３／ｈ烟气的工业性实验，汞蒸气的减少率η随气体温度的增加而减小，并与气体在电场中的停留时间ｔ、脉冲电压频率ｆ以及电晕功率Ｐ有关系式η１－ｅｘｐ（－ｋｆＰｔ）成立，对于初始浓度为２ｍｇ／ｍ＾３的汞蒸气，在一定条件下可达１００％的消除率。