Effect of Agricultural Chemicals on Aquatic Organisms

Incretion disturbance action of agricultural chemicals has recently become a serious concern. In particular, its effect on aquatic organisms has been alarming due to chemical substance exposure. This study developed an evaluation system for a testing method using biont.

Ricefish Used As Test Organism

The study made use of the d-rR strain of Oryzias latipes as a test organism, since its body color is closely related to its original sex, where the male is yellow and the scalpel white.

Sex Changes from Hormone Action Observed in Only Two Weeks

In the meantime, genital organs and the shape of the hip fin were altered by hormonal action. In this method, the genital organ of the scalpel was made into round hip fin. This way, it was possible to easily detect the sex transformation using these characteristics.

The young fish of Oryzias latipes was exposed to an examination substance for 2 weeks, and was later moved to breeding water without the examination substance, and allowed to breed for 40 days until the sex can be distinguished from its appearance. The color of the body, the hip form, and other characteristics were observed and the individual which exhibited sex change was investigated. The degree of the incretion disturbance was judged by this sex transformation rate.

By using this simple examination method, the laborious microscope observation of the reproduction system can now be avoided. Moreover, the chemical substance exposure period, which required 2 months or more, can now be shortened to 2 weeks.

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