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 ex amined 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 hi gh 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 t o 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, a nd 72-h exposure, respectively. Much higher toxicity (LC,, = 42 mu g l (-1)) was seen following chronic exposure of larvae to TBT. Acute expo sure to TBT significantly increased the time required by larvae to mol t 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, 4 8, and 72 h acute exposure, indicating that this earlier developmental stage was about 30-40 fold more susceptible to TBT than larvae. Horse shoe crabs are highly tolerant of TBT in comparison to early developme ntal stages of other marine arthropods. The ability of horseshoe crab embryos and larvae to survive in the presence of organotin pollution s uggests the possibility of bioaccumulation and movement into the estua rine food chain via shorebirds, gulls, and fish.