PW09 Pesticide I
8:00 AM - Wednesday
(PW158) Embryo Toxicology and Following Reproductive Effects of Carbaryl on Japanese Medaka.
Kashiwada, Shosaku1, 1 National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan
ABSTRACT- Chemical exposure on embryo stage gives critical stresses and irreversible morphological damages on organism. These stresses and damages cause an individual disease and/or following death that may reduce population and finally lead to extinction for inbreeding depression. To obtain thorough understands on chemical exposure to embryo and following influences on population must be essence for ecological risk assessment of chemicals. The aim of this study is to investigate ecological effects of chemical exposure to medaka embryo on development, growth and reproduction. Medaka embryo was exposed to 5 mg/L and 10 mg/L of carbaryl. DMSO was employed for carrier solvent at 0.1 % as well as control. The exposure was carried out at 26 °C with 18/6 hours light and dark photoperiod. A static-renewal exposure was employed to expose carbaryl and the solution was changed once a day. Carbaryl exposure allowed by embryo hatching, and then post-hatched embryos were moved to a flow-through incubation system with fresh and chemical-free water condition. Hatched Artemia fed at three times a day. Through exposure period, external and internal malformations; such as scoliosis, lordosis, kyphosis, tubular heart, microphthalmia, microcephalia, and edema in chest and jaw were observed. The exposed embryo exhibited declined heartbeat ratio and hatched fries were comparatively smaller than control fish in body length. Hatched fries were stained with calcein to observe skeletal development with fluorescent microscope equipped with GFP filter. Skeletal development in exposed medaka was not completed in the end of tail. This mean carbaryl exposure exhibited inhibition of skeletal development of medaka embryo. It would lead to a shortened body length of embryo. In meanwhile, there was no difference in hatching ratio among all tested embryo. A tubular heart and edema were the most sensitive biomarkers by carbaryl exposure, however survival ratio and body size of all exposed and hatched medaka were as same as those of not-exposed medaka in five weeks post-hatched. There was no longer observed morphological alternation except for jaw edema of exposed medaka groups. We will discuss influence of carbaryl-embryo exposure on following reproduction at presentation.
Key words: embryo, carbaryl, medaka, reproduction