Sea Angel

The sea angel is not a single organism but rather a group of marine sea snails called Gymnosomata. They are pelagic gastropods, meaning they favor open waters. They are translucent invertebrates.

It is believed that there are around eight families of sea angels throughout the animal kingdom. They prey on very similar animals called sea butterflies.

Appearance

Across the sea angel group, a wing-like structure has developed, which enables them to become mobile through the water. They can swim at speeds up to 0.22 mph. The wings are a decapod foot, evolved from the muscular foot of land snails, which can flap and allows them to be free-swimming marine creatures. These wings contribute to their ‘angel’ appearance.

Sea angels can get confused with their prey, sea butterflies, due to their similar appearance. However, the latter keep their shells after the larval stage, whereas the sea angel sheds its shell after only a few days.

The sea angel group are typically small, translucent creatures, averaging up to 5 cm in length. Their partially transparent body allows a view of their internal organs.

Diet

The sea angel feeds solely on other swimming sea snails called Thecosomata, or sea butterflies. One very picky species, Clione limacina, eat only sea butterflies from the limacina genus. They are so in sync with their prey that their feeding style has adapted over time to effectively navigate the thecosomata shell. They use small hooks and toothed radula instruments called buccal cones to eat their prey.

Their hunting strategies can vary from day to day. They switch between being ambush predators and more active hunters. They have perfected these strategies over many years.

Habitat

Sea angels are spread all across the world, living across a broad spectrum of oceanic habitats. They can thrive equally in polar regions and warmer tropical oceans alike.

They tend to occupy the upper section of the water column, normally living at around 65 feet (20 meters) depth but have been sighted as far down as 5,921 feet (1,805 meters)

Reproduction

The reproductive method of the sea angel is very interesting, as they don’t need any external influence to fertilize their eggs. They fertilize their eggs internally and then release them into the water column. Because they are protandrous hermaphrodites, over the course of their lives, they change genders from female to male. This means that they have both gametes, the egg, the sperm, and both reproductive organs. This allows the mating process to become extremely efficient.

Threats

Like many sea slugs and sea snail species, there are always threats from bigger marine animals, and they need to develop strategies to defend themselves. The sea angel is no different. A polar species called Clione antarctica, has developed a toxin called pteroenone, which acts as a chemical deterrent.

Interestingly, a tiny crustacean called an amphipod has been known to utilize them for its own defense, attaching itself to them and using them as a toxic shield. This chemical compound is the only example in which a chemical defense is produced by a mollusk.

Facts about the Sea Angel

• Sea angels feed purely on sea butterflies.
• They are hermaphroditic creatures, meaning they have both male and female sex organs.
• Sea angels can be found all over the world in pelagic zones.
• Some sea angel species are capable of toxic defense.
• Sea angels are thriving and are currently not under threat on the IUCN list.

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