Sea angels are small, free-swimming sea slugs that capture attention with their delicate, often transparent bodies. These pelagic gastropods possess unique wing-like structures, known as parapodia, which they use to propel themselves through the water. Their graceful movements contribute to their common name. Despite their angelic moniker, these creatures are active participants in marine ecosystems.
Geographical Range
Sea angels inhabit a wide range of marine environments across the globe, primarily favoring cold and temperate waters. They are commonly found in the frigid regions of the Arctic Ocean and the Antarctic Ocean. Their distribution extends into the cold areas of the North Atlantic Ocean, and specific populations have been noted in places like the Sea of Okhotsk. Some species also exist in deep, cold waters of other temperate oceans, and their presence can extend to equatorial regions. The largest known species, Clione limacina, is typically found in the colder northern waters, sometimes reaching sizes of up to 7-8.5 centimeters.
Environmental Conditions
Sea angels thrive in cold temperatures and varying depths. They are found from the ocean’s surface down to several hundred meters, typically inhabiting the midwater or mesopelagic zone. Some observations have recorded them at depths exceeding 1,800 meters.
Water temperatures in their habitats are often near freezing, particularly in polar regions. Their transparent, gelatinous bodies offer a degree of camouflage in the low-light conditions prevalent at these depths. Some sea angel species have developed specialized adaptations, such as producing antifreeze proteins, which allow them to survive in extremely cold waters without their bodily fluids freezing.
Life in Their Habitat
Sea angels are carnivorous predators, specializing in feeding on sea butterflies (free-swimming sea snails). They employ various hunting strategies, with some species acting as ambush predators, waiting for prey to pass by, while others actively pursue their targets. When a sea angel encounters a sea butterfly, it extends specialized finger-like tentacles called buccal cones from its head to grasp the prey.
These buccal cones are equipped with hooks and a radula, a toothed ribbon-like structure, which they use to extract the sea butterfly from its shell. The feeding process can take from a few minutes to 45 minutes. Sea angels propel themselves through the water by rhythmically flapping their wing-like parapodia, which are modified parts of their foot.
Their streamlined bodies contribute to their efficiency in movement and buoyancy. Sea angels often participate in diel vertical migration, following their sea butterfly prey as they move between deeper waters during the day and shallower waters at night. This behavior optimizes their foraging opportunities.