The betuline cone (Conus betulinus) is a large predatory and venomous cone snail, related to the textile cone.
It has a heavy shell that grows to up to 17 cm in length, and is distributed across the Indo-Pacific. The snail itself is velvet black and crawls around on a broad foot hunting worms.
In Hong Kong it occurs on sandy bottoms down to 5 m and in 1985 was still regarded common, although I haven’t ever seen a live one locally (yet!)
In contrast to the textile cone, the toxicity of the betuline cone is low. The toxins of cone shells are known collectively as conotoxins and act on the ion-channels regulating cells activities as well as on neurotransmitter functions.
The venomous Conus textile is one of the most abundant and widespread cone shell in Hong Kong waters. Easily recognized by the tent-shaped markings on the orange-colored cone-shaped shell with wavy chocolates lines, you are advised to stay away from these beautiful but dangerous reef predators. They like to hide in sandy patches under rocks and also occurs widely throughout the Info-Pacific and grow to a maximum of 15cm shell length. The danger they pose comes from a tiny venom-laden harpoon they can fire from their proboscis. They normally use this to hunt other sea snails by injection them with conotoxin through the harpoon-like needle teeth they can fire out of their proboscis. They can reach around to any point on their shell with this proboscis, and several human death have resulted from handling.
To see exactly how subtle and fast the venom injection is, I recommend this clip from YouTube of a textile cone in a tank hunting down a prey snail. The prey snail in the clip has actually sealed itself into its shell and shut the opening with a special door called an operculum – but apparently to no avail!