Sea Angel
A transparent thumb-sized mollusk that hunts a single prey species using tentacle-hooks that evert from inside its head
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Superpower
Sea angels (Clione limacina) eat only one prey species — sea butterflies (Limacina), a shelled pteropod. When a sea angel encounters its prey, it everts a set of six specialized tentacle-hooks from inside its head, grabs the sea butterfly's shell, and extracts the animal from inside it in seconds. This extreme dietary specialization means the sea angel's entire anatomy is tuned to a single prey — it cannot eat anything else.
Overview
Sea angels are naked pteropods — shell-less mollusks — that drift through polar and cold ocean surface waters worldwide, swimming using wing-like appendages in a motion resembling slow flight. Their transparent bodies reveal every organ including the contracting heart. Despite their angelic appearance they're ruthless predators. Some amphipod crustaceans have learned to collect and hold sea angels as chemical shields — sea angels contain compounds so distasteful to predators that being held by one provides meaningful protection.
Found in
Open ocean surface waters at high latitudes worldwide — Arctic, Antarctic, and cold North Atlantic and North Pacific. Found from the surface to several hundred meters depth.
Things worth knowing
- 1
Sea angels are used as living chemical shields by some amphipod crustaceans. The amphipods grab a sea angel, hold it against their body, and predators that would otherwise eat the amphipod avoid them entirely because of the sea angel's deterrent compounds.
- 2
The wing-like appendages of sea angels (parapodia) are so efficient that they can maintain position and hunt in currents that would carry other similarly-sized animals away.
- 3
Sea angels can survive weeks without food despite their highly specialized diet — when sea butterfly populations are low, they essentially pause metabolically while continuing to swim.
- 4
Sea angels are simultaneous hermaphrodites — every individual has both male and female reproductive organs and can mate with any other sea angel it encounters.
- 5
In polar regions, sea angel blooms can produce millions of individuals per cubic kilometer of surface water, creating a visible shimmer in the water column that has been observed from research vessels.