Sea angels are marine organisms known for their delicate, translucent bodies and graceful movements. Their angelic appearance has captured public imagination.
Understanding Sea Angels
Sea angels are a type of free-swimming sea slug, scientifically classified as gastropod mollusks. They belong to the clade Gymnosomata, a name that translates to “naked body,” reflecting their lack of an external shell in adulthood. A common species often studied is Clione limacina, found in various cold ocean regions.
Their Unique Features and Environment
These creatures possess translucent, often iridescent, gelatinous bodies. They are typically small, with the largest species, Clione limacina, reaching up to 5 centimeters in length. Their most distinctive feature is a pair of “wing-like” appendages called parapodia, which are modified from the muscular foot of their snail relatives. These parapodia allow them to propel themselves through the water with a rhythmic flapping motion, creating the illusion of flight.
Their transparent bodies help them camouflage and avoid predators in the open ocean. Their internal organs can sometimes be seen through their skin, occasionally displaying pink or orange hues. Sea angels inhabit a wide range of marine environments globally, from polar and subpolar regions to temperate and even tropical waters. They are pelagic organisms, meaning they live in the open water column, found from the surface down to depths exceeding 1,800 meters.
Survival in the Ocean Depths
Despite their delicate appearance, sea angels are active predators with specialized feeding habits. They primarily prey on “sea butterflies,” which are shelled pteropods, particularly species from the genus Limacina. Some sea angel species are ambush predators, while others actively pursue their prey, moving at speeds up to 10 centimeters per second.
When a sea angel encounters a sea butterfly, it extends specialized tentacles, known as buccal cones, from its head. These cones are equipped with chitinous hooks and sometimes a toothed radula, which they use to grasp the sea butterfly’s shell and extract its body. Sea angels are hermaphrodites, possessing both male and female reproductive organs. During mating, individuals engage in internal fertilization, after which they release gelatinous egg masses that float freely in the water until the larvae hatch. While sea angels are born with a small shell, they shed it during metamorphosis to adopt their adult, shell-less form.