A limnephilid caddis larva, Nothopsyche ruficollis (Ulmer), was used for development of a new acute toxicity test. The larvae were put in a Petri dish with test solution at 20°C and under a continuous light condition for 48 hours. One-day-old larvae just after constructing their cases were more suitable for the test than larvae of later stages because larvae of uniform size were easily provided from egg masses and had relatively long life without food. Susceptibility of the larvae to 5 kinds of insecticide, 3 kinds of herbicide, 2 kinds of fungicide and 5 kinds of inorganic compound (heavy metals and a cyanide) was examined. The larvae showed high susceptibility to insecticides, but not to other chemicals examined, especially heavy metals.

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Vitellogenin (Vtg), the egg yolk precursor protein, was purified from plasma of estradiol-17β (E₂) -treated juvenile Koi carp to homogeneity. The native Koi carp Vtg with a molecular mass of 300 kDa was a homodimer of an identical subunit with a molecular mass of 150 kDa. Absorbance at 280 nm and phosphorus content of the Vtg were 0.890/cm per mg of protein and 0.234µmol/mg of protein, respectively and are similar to those reported on gold fish Vtg. The N-terminus of the Koi carp Vtg was blocked, and deblocking was accomplished by digestion with pyroglutarnate aminopeptidase, suggesting that the N-terminal residue was pyroglutamate. The sequence of 30 amino acids after removal of the pyroglutamate was 59-83% identical to those of Vtgs from various fishes. The sequences of 2 internal peptides obtained by a digestion with V8 protease were 64-90% identical to those in internal regions of Vtgs from fathead minnow or rainbow trout. Ouchterlony and Western blot analysis demonstrated high specificity of a polyclonal antiserum raised in rabbit against the purified Koi carp Vtg. A homologous enzyme-linked immunosorbent assay (ELISA) was established using the antiserum and the Koi carp Vtg. The lowest detectable concentration by the ELISA was 10 ng/ml (at 95% binding), The intra- and inter-assay variations were respectively 4.5% and 7.2% at around 60% binding and those were 8.8 % and 14.6 % at around 95% binding. The ELISA was well applicable to determination of minute concentrations of Vtg in juvenile and male Koi carp plasma. The plasma Vtg levels in the juvenile Kai carp and the E2-treated juvenile Koi carp were 0.41 ± 0.12µg/ml (n = 30) and 57.2 ± 10.4 mg/ml (n = 11), respectively.

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A freshwater shrimp, Paratya compressa improvisa (Decapoda), was exposed in flowthrough aquariums to lake sediment contaminated with etofenprox (EFP, a synthetic pyrethroid insecticide) at 0.49, 9.98, 32.6 and 128 ng/g (wet wt.) for 30 h by spiking with EFP at 0,1, 2,0, 6,4, and 25.6 mg/L. Concentrations of EFP in the sediment decreased slowly in the flowthrough aquariums for 30 d, and remained at 60 and 70% of the initial concentration in the sediment treated with 6.4 and 25.6 mg/L EFP, respectively. Neither mortality nor growth of the. shrimps exposed to the sediment treated with 0.1 or 2.0 mg/1, EFP were affected. On the other hand, the mortality of the shrimps exposed to sediment treated with 6.4 mg/L EFP reached 100% by 7 days in the first part of the 35-d experiment, and was still approximately 76% in the latter period of the experiment. When the shrimps exposed to sediment treated with 6.4 mg/L EFP with commercial fish food, their mortality decreased to 20% compared to 76% of the unfed shrimp. Mortality of the shrimps exposed to the sediment treated with 25.6 mg/L EFP was 100% within 24 or 48 h throughout the 35-d experiment. However, shrimps introduced into the overflow water from this exposure-aquarium were not affected in either their growth or mortality. The EFP concentration of the sediment treated with 25.6 mg/L EFP was diluted with control sediment to 50%, 2.5% and 12.5%. Mortality of the shrimps exposed to these sediments decreased in relation to EFP concentration in the mixed sediment. All experimental results suggested that the high mortality of the shrimps is due to ingestion of EFP in the sediment rather than waterborne EFP exuded from the sediment.

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Abatement of the obstruction by Cr⁶⁺ to the mulberry growth was significant due to the addition of Fe²⁺ into the hydroponic solution. Compared with the blank samples, the visibleobstruction to the mulberry growth was severe, slight and invisible corresponding to thecharged concentration ratios of Fe²⁺ / Cr⁶⁺, 1/1, 3/1 and 5/1 (w/w), respectively. Meanwhile, the factors such as the shoot length, number of leaf number, chlorophyll concentration, dry weight growth, relative growth rate (RGR) and net assimilation rate (NAR) of mulberry were also affected significantly by adding Fe²⁺. These data supported the results obtained by the visual observation. Therefore, it was considered that the abatement of Cr6+ obstruction to the mulberry growth was probably resulted from two factors. The first one is that Cr6+ was reduced to Cr³⁺, which lightly obstructed the mulberry growth, due to the addition of Fe²⁺. The second one is that the residue of Cr⁶⁺ was just kept in the mulberry root after absorption, because the distribution of Cr⁶⁺ in the organs showed that a small amount of Cr⁶⁺ immigrated to the organs above the ground (the concentrations of Cr in the stern and the leaf was much lower than those without adding Fe²⁺). On the other hand, more than 3 times weight of Fe²⁺ to Cr6+shouId be required for thoroughly abating the obstruction of Cr⁶⁺..Key words: divalent iron ion, hexavalent chromium ion, mulberry, growth obstruction, ameliorative effects

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Many adult water beetles and adult water bugs hold the bubble or layer of air in unwettable hairs or under the wings for under water respiration. Such a respiration system is called plastron respiration. It was suggested that a respiration blocking is caused by treatment of surfactants for aquatic insects that does plastron respiration. So, the acute influence test of surfactants was done by using three species of water bugs and two species of elmid beetles with plastron respiration. As a result, it was found that the aquatic insects with plastron respiration were more influenced by treatment of surfactants than Daphnia magna, and the sensitivity of surfactants was especially high in elmid beetles.

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Suseptibility to insecticides in the giant water bug, Diplonychus major Esaki, was examined. The test insecticides were organophosphates (fenitrothion ), pyrethroids (ethofenprox and cycloprothrin), and neonicotinoids (imjdaoroprid)、The giant water bug showed high susceptibility to pyrethroids, ,i.c., , LG50s of ehhofenprox and cycloprothrin were 0.89 and 1.77μg / L, respectively. LC50s of fenitrothion and imidacroprid were 24.6 and 54.7 μg / L, respectively. respectively.

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