Most venomous gastropods

The most venomous gastropods, and among the most venomous of all animals, are cone snails of the genus Conus, which can deliver a fast-acting neurotoxic venom called conotoxin via a harpoon-like barb. Several of these species are venomous enough to kill humans, but the geography cone (Conus geographus) of the Indo-Pacific is considered to be the most dangerous, having been responsible for the most deaths – some three dozen in the last 300 years (the earliest report dating back to 1705).

Other cone snails can be equally as dangerous, especially the textile cone (C. textile).

Human fatality rates among those envenomated by geography cones have been reported as high as 65–70%.

Only very small amounts of conotoxin can prove fatal, demonstrating its potency. In 1984, Japanese scientist Professor Shigeo Yoshiba (then of the Jikei University School of Medicine in Tokyo) estimated that a lethal dose of conotoxin could be as little as 0.001–0.003 mg/kg (1–3 µg/kg) in amounts corresponding to LD70 in humans. This is the amount, in relation to body weight, that kills 70% of those envenomated, i.e., for an average 70-kg adult man, only 0.14 mg of venom has a 70% chance of causing death. In two cases, just 0.2–0.5 µg/kg of conotoxin resulted in severe paralysis. Other studies suggest a slightly higher threshold: an LD50 (a lethal dose that causes death in 50% of cases) of 0.012–0.030 mg/kg; this would still put it on a par with the most venomous snake, the small-scaled snake (Oxyuranus microlepidotus), aka the inland taipan, of Australia.