[Luring effect of the fermented Laminaria japonica to Oncomelania hupensis].

OBJECTIVE: To study the attraction effect of the food attractants on Oncomelania hupensis. METHODS: Oncomelania snail food was prepared with the fermented kelp (Laminaria japonica) mixed with corn starch. Snails were fed with the food and kept for 12, 24, 36, and 48 h at 15, 25, 35 degrees C respectively. Meanwhile, snail-killing effect was tested by granules containing jack-in-the-pulpit (Arisama heterophyllum) with or without the fermented kelp under the condition of 25 degrees C, 30% or 60% soil humidity. RESULTS: The snail-attracting rate of the fermented kelp was affected by the temperature, highest under 25 degrees C and lowest under 35 degrees C at any time point, with a rate of 80.3% in 48 h at 25 degrees C which was higher than that of the control (17.0%) (P<0.01). The snail mortality rate in the group using jack-in-the-pulpit with fermented kelp (85.3%) was higher than that of the group without fermented kelp (26.8%) (P<0.05). The mortality under 60% of soil humidity was higher than that under 30% humidity (P<0.01). CONCLUSION: The fermented kelp shows a strong luring effect to the Oncomelania snails.

Visible light induced photodegradation and phototoxicity of phloxine B and uranine.

OBJECTIVE: To determine the visible light-induced photodegradation kinetics of two xanthene photosensitizers, phloxine B and uranine, in solution and on the surface of silica TLC plates, and to examine the phototoxicity of residues of degradation, which could provide valuable safety data on the two photosensitizers and other xanthene chemicals when applied in the environment. METHODS: UV-Vis absorption during photodegradation was monitored with a Unico 2102 spectrophotometer. Organic content of samples was measured with a Shimadzu TOC 4100. Phototoxicity tests were carried out using Saccharomyces cerevisiae with the methods modified from Daniels. RESULTS: When phloxine B and uranine degraded in solution, their apparent rate constant k was 0.0019 and 0.0027 min(-1), respectively. The total organic carbon (TOC) content decreased by approximately 50% during the 8 h irradiation period, which led to a gradual decrease in phototoxicity of the residues. The photodegradation of photosensitizers on the surface of silica TLC plates was much faster than that in the solution. The apparent rate constant k and the half life of phloxine B were 0.0073 min(-1) and 95 min, respectively. CONCLUSION: Visible light can rapidly induce photodegradation of phloxine B and uranine. The phototoxicity of residues is also decreased. The environmental risk of applications of phloxine B and uranine is minimal.

Molluscicidal activity of Nerium indicum Mill, Pterocarya stenoptera DC, and Rumex japonicum houtt on Oncomelania hupensis.

OBJECTIVE: To evaluate the molluscicidal activities of three Chinese plants N. indicum Mill, R stenoptera DC, and R. japonicum Houtt, and to clarify the molluscicidal mechanism. METHODS: N-butanol extracts and water extracts of the three plants were obtained. The reactions of EST isozyme, glycogen and total protein of snails to the plant extracts were studied. RESULTS: EST electrophoresis showed that EST was an important antidotal enzyme system and reacted strongly to environment. EST changed greatly during the whole exposure period so that it could be viewed as a pathological index of toxicity. Extracts decreased the glycogen content of the snails' soft tissues greatly, and also the protein content. CONCLUSION: All extracts show strong molluscicidal activity. The LD50 value of the water extract of N. indicum Mill is as low as 13.2 mg/L. EST can be viewed as a pathological index of toxicity. The energy metabolism abnormity is the key reason for the molluscicidal activities. The biochemical mechanism needs further research.