Cone snails that hunt and eat fish are called piscivores. There are two different kinds of fish hunters: hook-and-line hunters and net hunters.
Hook-and-line hunters use their proboscis like a fishing line. The snail will use its siphon, a nose-like organ, to search for prey in the surrounding waters. If the snail detects fish, it will extend its proboscis (this organ can extend to be twice the length of the snail's body). The proboscis contains a venomous harpoon, which is shot into the fish when the proboscis makes contact with the fish's body. The venom from the harpoon enters the fish and instantly paralyses it. The venom is a mixture of conotoxins that are able to paralyze the fish in different ways. Hook-and-line hunters need the fish to be rigid and stiff so they can pull it into their mouths. They inject a venom that elicits an excitotoxic shock. At first the fish will jerk rapidly and then within seconds the fish will become stiff and immovable. Its fins will be fully extended, unable to hurt the cone snail or escape. The harpoon is barbed and will keep the fish tethered to its proboscis. This is very similar to a fishing line with barbed bait. The fish is then quickly reeled back into the snail's mouth to be eaten. The venom mix will also contain longer acting toxins that cause flaccid paralysis. This type of paralysis causes the fish to be completely limp.
The net-hunters expand their mouth outwards to engulf several fish at a time. Some net hunters have finger-like projections on the outside that might trick the fish into thinking it is an anemone. The expanded mouth may also look like a cup coral or a hiding place in the reef.
Then look at this beautiful picture of a sea anenome and a skunk clown fish, taken by national geographic.
Once the fish are inside the mouth, the cone snail will harpoon its catch to paralyze it. Net-hunters only use flaccid paralysis in their toxins. Conus geographus is a great example of a net-hunter. Watch a video that shows a geography cone expanding its huge mouth in our video gallery!
Scientists believe that the cone snail releases chemicals into the water to sedate the fish so that they aren’t very active. Most cone snails are nocturnal, which means that they are active at night when fish are sleeping. Once the fish is digested, which may take many hours to days, the snail will spit out the fish’s bones, the harpoon, and any sand or gravel that was also swallowed.