Jewels of the seabed

Edited version:

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All that glitters. Sea slugs compensate for their small size and soft bodies by advertising their poisons through colour.Photo: Vardhan Patankar

If you dive deep into the oceans, you could be treated to a view of colourful sea slugs. While you admire the patterns and hues, be informed – the colours are their armours.

Enchanting to anyone who dives beneath the ocean’s surface, colourful sea slugs are a diverse group of marine animals that are found all over the world. The photos speak for themselves; take a closer look and prepare to be assaulted by an assortment of patterns and hues ranging from black-and-white to psychedelic colours.

Unlike the dull brown slugs that we see on land, sea slugs are amongst the most spectacular and diverse creatures that can be found in the world’s seas, from shallows and reefs to murky sea beds nearly a mile under the sea surface. They are molluscs, belonging to a group called Opisthobranchs.

Gaze at the bright blue, vivid violet, flaming yellow, plum-like purple on sea slugs, and you will be left awestruck by the range of colours on the display. If you could ask a sea slug the secret of their beauty, they’d tell you that their colours are there for a reason: to protect themselves from predators! Isn’t that strange? How could colours keep them safe in an environment swarming with voracious feeders, from sharks to barracudas and much more?

A play of evolution

To understand this you’d have to look at their history. The ancestors of sea slugs discarded their hard and protective shells millions of years ago, and today’s sea slugs are just soft organs, muscle and skin. So how do they protect their soft, vulnerable bodies?

This is how. They make themselves distasteful to any animal that tries to eat them and advertise this in their colours. The message to predators is loud and clear: “Don’t eat me, I’m poisonous !” Although almost all sea slugs are colourful, different kinds have different ways of protecting themselves.

Store poison

Some are tough-skinned and bumpy, whereas others are armed with toxic ink jets or even stinging cells. Their food (sponges, fire corals and anemones) contain poison. After digesting their food, sea slugs store the poison and secrete it from their skin cells or glands when eaten. This means that any animal that tries to eat a sea slug probably makes a face similar to yours when you are made to eat vegetables like a bitter gourd!

Pretty interesting, right? Well, this is only a small sample of what is known about sea slugs, and in fact, there is a lot that is still unknown. Researchers are still discovering new species and behaviours with flamboyant displays of colours. For me, seeing these fabulous animals underwater is like seeing abstract paintings: allowing you to experience the extraordinary sea slug in an astonishingly unusual way.

Spectacular sea slugs

  • There are over 3,000 species of sea slugs, and new species are still being discovered.

  • Sea slugs have a foot, and they leave a slimy trail, just like land slugs.

  • They have a short lifespan; some live up to a year, others only a few weeks.

  • Sea slugs are both genders at the same time – so they are hermaphrodites.


Edited version:

Published by Vardhan Patankar


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