All about the deadly sea angel featured in Planet Earth 3

The latest episode of Planet Earth 3 introduced us to a tiny creature of the deep, the see angel.

The first episode of the new series, presented by David Attenborough, looked into the animals around our coasts.

The sea is a realm filled with wonders both great and small, and one of its most captivating tiny inhabitants is the sea angel. Despite its name, the sea angel is not a celestial being but rather a fascinating marine creature found in the cold, dark waters of the world’s oceans. In this article, we’ll delve into the intriguing world of the sea angel.

Sea angels belong to the family Clionidae and are a type of pelagic sea slug. They are characterized by their ethereal appearance, which has earned them their celestial name.

Sea angels are translucent, gelatinous creatures with a delicate, wing-like structure that allows them to “fly” through the water. Their bodies are typically no larger than a few centimeters, making them almost invisible in their natural habitat.

A sea angel in the sub-Arctic waters of Russia's White Sea.
A sea angel in the sub-Arctic waters of Russia’s White Sea. © Alexander Semenov/BBC

Sea Angel Habitat and Behavior

Sea angels are primarily found in the frigid waters of the Arctic and Antarctic oceans, where they thrive at depths ranging from the surface down to several hundred meters.

Unlike their close relatives, sea butterflies, which have external shells, sea angels lack a protective shell and instead rely on their unique body structure to maintain buoyancy.

These creatures are carnivorous and feed on another remarkable oceanic species: the sea butterfly. They have specialized mouthparts adapted for grasping and consuming their prey.

Sea angels are themselves prey for larger marine animals such as fish, making their existence in the ocean a constant battle for survival.

Complex Life Cycle

One of the most intriguing aspects of sea angels is their complex life cycle. They are simultaneous hermaphrodites, meaning they possess both male and female reproductive organs.

During mating, sea angels engage in a mesmerizing dance, exchanging sperm packages. Once fertilization occurs, they produce a transparent egg mass, which eventually hatches into larval sea angels.

The larval stage of sea angels is known as a “veliger,” and it closely resembles the appearance of a snail. During this phase, they are free-swimming and feed on plankton until they metamorphose into the adult sea angel form. This remarkable life cycle ensures their survival in the harsh oceanic environment.

Significance and Conservation

Sea angels may be small, but they play a vital role in the marine ecosystem by controlling the population of sea butterflies, which are known to feed on phytoplankton.

Phytoplankton is a primary food source for many marine creatures, so sea angels indirectly impact the entire food web.

While sea angels are not currently considered endangered, they are susceptible to changes in ocean temperature and acidity due to climate change. Any disruption to their habitat could potentially affect their population and the broader marine ecosystem.

In conclusion, the sea angel is a tiny marvel of the deep, a translucent, winged sea slug that glides gracefully through the icy waters of polar oceans.

Its unique appearance, complex life cycle, and ecological significance make it a captivating and enigmatic creature of the sea, reminding us of the remarkable diversity found in Earth’s oceans, no matter how small the inhabitants may be.

Watch Planet Earth III on Sunday nights on BBC One.

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