EFFECT OF DIETARY 1,3,6,8-TETRACHLORODIBENZO-P-DIOXIN ON THE JAPANESEFRESH-WATER FISH ORYZIAS-LATIPES (MEDAKA) AND AQUATIC SNAIL INDOPLANORBIS-EXUSTUS (INDOHIRAMAKIGAI)

During the Japanese spring , many tons of herbicide are used to contro l weeds in rice paddies . Some of these herbicides are contaminated wi th 1,3,6,8-tetrachlorodibenzo-p-dioxin ( 1368-TCDD ) and have given ri se to residue levels of up to 40 ppb in some Japanese aquatic species Japanese Medaka ( Oryzias latipes ) and Indohiramakigai ( Indoplanorbi s exustus ) snails were chosen to represent aquatic species that might be exposed to elevated levels of agriculture derived 1368-TCDD . The Medaka were challenged with food contaminated with 40 ppb - 400 ppm 13 68-TCDD , and the Indohiramakigai allowed to feed on the resulting det ritus . Grab samples of both fish and snails were analysed for 1368-TC DD by GC-HRMS-SIM . Results show that the Medaka absorbed only 0.05 -0 .1 % of the dioxin content of their food and that the absorbed 1368-TC DD was almost totally depurated within 56 days . The Medaka appeared t o suffer no harmful effects , even at the highest doses . Indohiramaki gai snails were very much more efficient at absorbing 1368-TCDD from t heir detrital food source . Their populations were reduced dramaticall y , even at the lowest dioxin dose.