This strange dinky glowing ocean creature, which disguises itself as a moonbeam and dies as soon as it breeds, amazes scientists at night

In the shallow, sandy coastal waters of Hawaii lives an intriguing animal that mesmerises the general public and scientists alike. It is as small as a golf ball but has intriguing qualities that keeps it safe from much larger predators.

You'll spot it easier at night time than in the day – when it buries itself in the sand – as it glows brightly in the dark. The animal in question is the Hawaiian bobtail squid.

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What is a Hawaiian bobtail squid?

Bobtail squids are a family of small cephalopods named Sepiolidae, native to the Pacific Ocean. They are named so because of their small size and rounded mantle (main part of its body). They live in shallow waters; the Hawaiian bobtail squid (Euprymna scolopes) is found in the Hawaiian archipelago.

What does a Hawaiian bobtail squid look like?

The pear-shaped Hawaiian bobtail squid is mottled in colour, which it can change with the help of colour-producing cells called chromatophores. It has large (for its body) paddle-shaped fins that help it swim. It also has large eyes and tentacles.

Its brain is enormous compared to its body size, and complex. The females can grow larger than the males (up to 6.5cm).

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What does a Hawaiian bobtail squid eat?

This small squid is a nocturnal predator, preying on small shrimp and crustaceans. In the day it buries itself in the sand to hide from predators – the Hawaiian monk seal and the lizardfish.

Why does a Hawaiian bobtail squid glow at night?

The Hawaiian bobtail squid creates an extraordinary light show that it uses for camouflage. The cephalopod is able to become 'invisible' thanks to a symbiosis with bioluminescent marine bacteria called Vibrio fischeri, which lives insides its light organ, located in the mantle.

It works like this: predators search for shadows cast by prey; sensors on the squid's mantle measure the intensity of moonlight and project an equal beam from their light organ; the brightness below is matched to that above – all the predator sees is what looks like a single unbroken moonbeam. It's incredible!

What triggers the light show?

The squid-Vibrio symbiosis has caused marine biologists to investigate, among other things, a fascinating process called quorum sensing: only once the density of Vibrio reaches a critical mass, or quorum, do the bacteria all turn on their lights, and then the light show can begin.

This is thought to be made possible by a molecule known as an autoinducer, which allows the Vibrio to communicate and "perform" in unison.

Do baby Hawaiian bobtail squids glow?

Hatchling Hawaiian bobtail squids do not glow from the off because they are not born with the bacteria that makes them glow. However, a few days after they emerge from the eggs they begin to secrete a mucus that attracts the symbiotic bacteria.

There's a benefit to getting through to the squid's mantle for the bacteria – they are fed and can increase their population.

How long do Hawaiian bobtail squid live?

These small cephalopods live a short time in the wild – estimates range from two to ten months. Females die after laying eggs and males die almost immediately after fertilisation.

This article originally appeared in BBC Wildlife as an interview with comedian Rob Newman about his fascination with Hawaiian bobtail squids.

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Main image: Getty Images