Imposex induction in the mud snail, Ilyanassa obsoleta, by three tin compounds.

摘要

The induction of imposex in mud snail (I. obsoleta) following exposure to trioctyltin chloride (TOT), dioctyltin chloride (DOT) and tin tetrachloride (TTCI) was investigated. Snails received 20 ng TOT, DOT or TTCI in an injection volume of 5 micro litre every other day for 7 or 14 days. Aqueous exposures were carried out in sea water treated with each of the tin compounds or tributyltin oxide (TBT) at 5, 10, 20 or 50 ng/litre. Imposex induction was determined by calculating the percentage of females bearing a penis or penis bud. The tin compounds induced imposex in snails. TBT was the most potent among the compounds. Imposex induction reached 35, 15 and 18% for TBT, TOT and TTCI, respectively. Aqueous exposure to TBT resulted in a 35-40% induction of imposex, compared to 25-27% for TOT, 18-19% for DOT, and 21-23% for TTCI. The induction of imposex occurred in a rate-dependent manner in the aqueous exposures. At 50 ng/litre, imposex induction was greatest for TBT, followed by TOT, DOT and TTCI, which were on a par. Female snails exposed to TBT exhibited a marked and dose-dependent increase in the relative penis size index (RPSI), reaching 0.74. The effect observed in animals exposed to TOT, DOT and TTCI was minimum (< 0.10). This indicated that exposure to octyltin and tin tetrachloride are sufficient for the initiation of the growth of accessory sex organs, but these compounds do not appear to be as effective as TBT in stimulating neuronal and/or hormonal factors necessary for supporting full development of imposex characteristics..