Fish embryo toxicology is important because embryos are considered more susceptible than adult fish to the effects of toxic chemicals. Recently, fish embryo bioassay was proposed to replace the conventional fish acute toxicity chemical test of the Organization for Economic Cooperation and Development guidelines because it offers the advantages of fewer reagents, easy handling, and efficient data production. To accelerate the establishment of a chemical toxicity database for the protection of environmental and human health, we need to determine whether the conventional toxicity test can safely be replaced by such fish embryo toxicity tests. For instance, it is unclear how the presence of the chorion moderates the toxic effects of some chemicals. If such chemical toxicities do differ between embryos and, for example, the larval stage, then different toxic effects should appear in later life. We tested the later-life effects of the neurotoxic insecticide carbaryl at sublethal concentrations (0 [control] and 5 and 10 mg/L) in embryos and posthatch larvae of the freshwater fish medaka, Oryzias latipes. Although embryos exposed until hatching showed multiple developmental malformations and reductions in subsequent survival rates over three months, no significant reduction was observed in tolerance to starvation for 7 d and in intrinsic population growth rate (r). Exposure of larvae for 96 h resulted in dose-responsive vertebral fracture, significant reduction in tolerance to starvation for 7 d, and reduced three-month survival rate; r was reduced significantly and consistently. These results suggested that posthatch larvae were more susceptible than embryos to carbaryl exposure and that the toxic cascades may differ between larvae and embryos. The influences of carbaryl exposure on population growth rate differed significantly with developmental stage.

14C-heptachlor for 72 hr. The levels and nature of 14 C-residues in roots and shoots of treated plants were determined to estimate the values of the root concentration factor (RCF) and the transpiration stream concentration factor (TSCF). RCF and TSCF values ranged from 126 (corn) to 4086 (lettuce) and 0.052 (Chinese cabbage) to 0.494 (zucchini), respectively. In pumpkin and zucchini, unmetabolized heptachlor itself was translocated from the root to the shoot via a transpiration stream and no further extensive metabolism was observed. cis-Heptachlor epoxide was the predominant metabolite in the shoots of tomato, cabbage, Chinese cabbage and lettuce. Less metabolism of cis-heptachlor epoxide was suggested in the shoots of these plants.

The release of the larvae of flightless ladybird beetles could extend the duration of effective control because of the longer presence of adult stages, and the per individual production cost for juvenile stages is lower than that for adult stages. A preliminary release experiment was conducted to assess the effectiveness in controlling two aphid species, Aphis gossypii and Aulacorthum solani, using second instars of a flightless strain of Harmonia axyridis. The number of A. gossypii was suppressed in greenhouses that contained the flightless strain compared with greenhouses that contained the wild‐type strain. In one of two replicates, more flightless adults were observed on the plants for longer than wild‐type adults. However, it was not clear whether the extension of the residence period contributed to the effectiveness in controlling aphids directly, because the population of ladybirds in the greenhouses consisted of both larvae and adults during parts of the experimental period. In flightless H. axyridis, the release of larvae was more effective in suppressing A. solani than the release of adults. These results suggest that it may be more effective to release larvae of flightless H. axyridis than wild‐type larvae or flightless adults.

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The fate of [(14)C]heptachlor in Saitama soil and the degradation of [(14)C]heptachlor in four Japanese field soils over 112 d after application were investigated. Heptachlor was degraded mainly to cis-heptachlor epoxide by a biotic process and to 1-hydroxychlordene by an abiotic process in the field soils. Volatilization of heptachlor and cis-heptachlor epoxide from the soil was observed over the experimental period. The amount of 1-hydroxychlordene produced in the soils appeared to be related to the soil water contents. Because heptachlor and heptachlor epoxides are predicted to volatilize to the atmosphere and to persist in soils, these compounds are thought to spread among Japanese environmental compartments even after a ban on their use.