It is generally recognized that amphibian populations are potentially sensitive to aquatic contaminant such as herbicides. However, studies on the effects of herbicides on amphibian species are very ...limited in Japan. Thus, the toxicity of herbicides for paddy field to the tadpole of Rana dybowskii was examined by the author. Among the eight herbicides tested, only Fujigrass® has a high toxicity to the tadpole. Moreover, based on a comparison of the components of herbicides between the Fujigrass® and other non-toxic herbicides, it has become apparent that esprocarb (1,2-dimethlpropyl (ethyl)-thiocarbamate), the principal component of Fujigrass®, is the toxic substance to the tadpole of Rana dybowskii.
Ovipositional preferences of Helicoverpa assulta and Helicoverpa armigera femalesfor several host plants were investigated. Among the five host plants tested, the H. assulta female showed a strong ...ovipositional preference for tobacco only. On the other hand, the H. armigera female showed a weak ovipositonal preference for the five host plants tested, but the net which covered the insect rearing cage had a significantly (p <0.05) greater number of eggs. This suggests that the H. armigera female exhibits a unique characteristic, that is, it oviposites anywhere else than the host plants.
The rice grasshopper, Oxya yezoensis, exhibits 3-color polymorphism: red, green, and brown. We studied whether differences in insecticide susceptibility occurred with the 3 color morphs. No ...significant difference was detected among them.
Toxicities of insecticides to three kinds of fresh water snails were evaluated. The test organisms are Physa acuta, Semisulcospira libertina and Cipangopaludina chinensis. The fresh water snails are ...quite low susceptible to insecticides and LC50 values of organophosphates, pyrethroids, and neonicotinoids ranged from 0.84 to >100 ppm.
Toxic chemicals released into the aquatic environment do not exist independently but coexist and they have complex and interactive effects on aquatic organisms. In some cases, it is considered that ...they have synergistic effects. Therefore it is very important to detect quickly and easily interactive effects of toxic chemicals in order to preserve the environment from chemical pollution. In this study, interactive effects among heavy metals and agricultural chemicals, Imidacloprid, were investigated using Daphnia magna. The data were analyzed by the method of Isobologram, where a traditional swimming inhibition test and a mobility analysis test proposed by the authors were used. The experimental results were as follows; the interactive effect of lead (Pb2+) vs. Cadmium (Cd2+) was synergistic, Cd2+ vs. Zinc (Zn2+) and Pb2+ vs. Zn2+ were antagonistic, Imidacoprid vs. Pb2+ was antagonistic and Imidacloprid vs. Zn2+ was additive. We could get a high correlation between a traditional swimming inhibition test and a new mobility inhibition test using D.magna.
The insecticides susceptibility of adults of the water strider, Gerris latiabdominis, was studied. The water strider is quite susceptible to insecticides and the LD50 values of organophosphates, ...carbamates, pyrethroids, nereistoxins, and neonicotinoids ranged from 0.24 to 31.6μg/g. The LD50 values for fenitrothion, BPMC and PHC were low compared to those for several Hemipteran insect pests of rice paddy.
We investigated the aquatic insect fauna of two streams in the Daisetsuzan National Park; the Hokkaizawa Stream (144°60.33'E, 41°5.48'N, 1, 840ma.s.l.) and the Akaishi Stream (144°65.58'E, ...41°20.54'N, 1, 830ma.s.1). Of the 10 taxa were collected in the Hokkaizawa Stream, Apatania sp. (Trichoptera) were dominant. In the Akaishi Stream, among 3 taxa collected, Nemoura spp. (Plecoptera) were dominant. There were no taxa common to the two streams. The Akaishi Stream has a mean pH of 3.1. This acidic pH accounts for the different species composition of aquatic entomofauna in the two streams.
Ratio of brown, green and red types of female Oxya yezoensis was researhed every week in Akita Prefecture from August to November in 1997. The ratios of each type were kept constant, i.e., brown (ca. ...70%), green (ca. 30%) and red (0-3%) type. With respect to adult size and susceptiblity to ethofenprox, there were no significant differences in the three color types.
Feeding responses of Helicoverpa armigera and H. assulta to Solanaceae plants were investigated. Among the five plant diets (eggplant leaf, eggplant fruit, tomato leaf, tomato fruit, and tobacco ...leaf) and artificial diet (Insecta LF) tested, H. armigera had the highest preference for eggplant fruit, whereas H. assulta had equal preference for eggplant fruit, insecta LF and tobacco leaf. We also investigated the feeding responses of both species to methyl alcohol extracts of Solanaceae plants. H. armigera had equal preference for the methanol extracts of eggplant fruit, eggplant leaf, tomato fruit and tobacco leaf, whereas H. assulta preferred that of tobacco leaf. These results suggest that the feeding stimulants that exist in Solanaceae plants for H. armigera and H. assulta are slightly different.
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