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 μg l−1 TBT. Survival was also high following 48-h and 72-h exposure to ≤100 μg l−1 TBT; >50% mortality was seen only after 48-h and 72-h exposure to 500 μg l−1 TBT. Estimated median lethal concentrations (LC50) were >1000 μg l−1, 742 μg l−1, and 594 μg l−1 for 24-h, 48-h, and 72-h exposure, respectively. Much higher toxicity LC50=42 μg 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. LC50 for horseshoe crab embryos exposed to TBT were 44 μg l−1, 20 μg l−1, and 14 μg 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.