In the dark depths of the ocean, sea angels gracefully navigate the depths with their mesmerizing wings. These ethereal creatures captivate scientists and marine enthusiasts alike with their celestial beauty. Join us on a journey to explore these mysterious creatures, uncovering the facts and secrets behind these angels.
Phylum: Mollusca
Class: Gastropoda
Clade: Gymnosomata
1. Sea angels are snails
Meet the mesmerizing and enigmatic sea angels, scientifically referred to as Gymnosomata, as they grace the vast oceans with their presence. These extraordinary beings are none other than miniature sea slugs with exceptional swimming abilities. Embraced within the group Pteropods, alongside their fellow sea butterflies, these alluring “naked body” sea slugs effortlessly capture the fascination of all who encounter them with their graceful aquatic maneuvers.
With a size of a mere 5-centimeter length, these mesmerizing angels by the sea gracefully glide through the ocean, executing pulsating motions reminiscent of an attractive dance. They move through water at speeds of up to 0.22 mph, all thanks to their wing-shaped extensions. These characteristics grant the sea slugs their name and look.
Sea angels have a transparent, gelatinous bodies that show you all of their inner organs, such as pulsating hearts and orange-pink reproductive gonads. All of these, as well as their elegant movements, lend them an almost otherworldly and ethereal charm.
These creatures bear a pair of prominent horns atop their heads, presumed to function as sensory organs since they lack any form of eyes.
Sea angels are often mistaken for sea butterflies due to their striking resemblance. Nonetheless, a crucial distinction can be found in their shells. While sea butterflies retain their shells throughout their larval stage and beyond, sea angels cast off theirs within a mere few days.
2. Habitat
Sea angles can be found across the globe. They demonstrate remarkable adaptability to diverse oceanic settings, spanning from the icy polar regions of the Subarctic and Arctic oceans to the warmer tropical waters of the Atlantic and Pacific oceans.
They live in the higher realms of the water column, at a wide range of depths. They can locate at a depth of around 65 feet (20 meters) to astonishing lows of about 5,921 feet (1,805 meters).
3. They’re formidable hunters
In the realm of the ocean, sea angels, with their alluring elegance and celestial name, harbor a surprising nature as ruthless carnivores. Their primary diet consists of their close relatives – the delicate sea butterflies.
As they come across their prey, the sea slugs display a diverse array of hunting techniques, seamlessly transitioning between ambush strategies and proactive pursuit, leveraging their impressive speed and agility to secure their targets. With a transparent look, you can see their beating heart when they come in to attack the prey.
When a sea butterfly comes into the picture, the angel employs finger-like tentacles emerging from its head to seize the prey. Following that, it deploys specialized hook-shaped appendages called buccal cones, which are equipped with numerous hooks and a toothed radula, to draw the sea butterfly out of its shell and eat it. This whole procedure can take anywhere between 2 to 45 minutes.
Sea angels are important prey for various marine predators, including jellyfish, baleen whales (blue whales or humpback whales), fishes, ctenophores, and birds. To protect themselves, they have developed ingenious ways.
With their transparent bodies, these species can blend into the deep ocean, hiding themselves from potential predators. Moreover, they have evolved chemical defenses, with certain types of sea angels producing toxic compounds called pteroenone that repel fish and discourage them from being eaten. However, most of them are harmless, they don’t have poison or venom.
4. They can change gender
Like other sea slugs, sea angels are hermaphrodites, meaning they possess both male and female reproductive organs. This unique trait makes their search for suitable mates for reproduction easier.
To reproduce, these species engage in a mating ritual where they stick to each other for extended periods. The fascinating process involves the inversion of their reproductive organs, aided by specially adapted suction cups that keep them firmly united.
The remarkable feature that distinguishes sea angels is their capacity for changing genders during their lifetime, known as protandrous hermaphroditism. They begin as males and subsequently undergo a transformation into females. You can see this trait in other fish species that can change gender.
This unique gender-shifting ability empowers the sea slugs to internally fertilize their eggs, without relying on external factors. After mating and fertilization, they emit their eggs into the water column as a freely drifting cluster.
As sea angels progress towards adulthood, they embark on a fascinating metamorphosis, akin to a caterpillar’s wondrous evolution into a butterfly. These species begin their lives with a shells, however, they ultimately discard this protective covering to embrace their new form as delicate, soft-bodied beings. The lifespan of sea angels extends up to 2 years.
5. Threats
Similar to many marine organisms, sea angels and their food sources could be greatly affected by ocean acidification and rising ocean temperatures.
These sea slugs primarily depend on sea butterflies as their food source and sea butterflies rely on calcium carbonate to construct their shells. However, the changing ocean chemistry is reducing the availability of calcite and aragonite needed for shell formation. This could potentially result in decreased sea butterfly populations.
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