High tolerance to tributyltin in embryos and larvae of the horseshoe crab, Limulus polyphemus

The effects of acute and chronic exposure to tributyltin (TBT) were examined in bioassays using horseshoe crab (Limulus polyphemus) embryos and "trilobite" larvae. Larvae had >95% survival after 24-h exposure to nominal concentrations of 1-500 mu g I-1 TBT. Survival was also high following 48-h and 72-h exposure to less than or equal to 100 mu g l(-1) TBT; >50% mortality was seen only after 48-h and 72-h exposure to 500 g l(-1) TBT. Estimated median lethal concentrations (LC50) were >1000 mu g l(-1), 742 mu g l(-1), and 594 mu g l(-1) for 24-h, 48-h, and 72-h exposure, respectively. Much higher toxicity (LC,, = 42 mu g l(-1)) was seen following chronic exposure of larvae to TBT. Acute exposure to TBT significantly increased the time required by larvae to molt into the first-tailed stage. LC,, for horseshoe crab embryos exposed to TBT were 44 mu g l(-1), 20 mu g l(-1), and 14 mu g l(-1) for 24, 48, and 72 h acute exposure, indicating that this earlier developmental stage was about 30-40 fold more susceptible to TBT than larvae. Horseshoe crabs are highly tolerant of TBT in comparison to early developmental stages of other marine arthropods. The ability of horseshoe crab embryos and larvae to survive in the presence of organotin pollution suggests the possibility of bioaccumulation and movement into the estuarine food chain via shorebirds, gulls, and fish.