Cuttlefish: luminous squid and its bacterial buddies
Cuttlefish: luminous squid and its bacterial buddies
Probably the cutest couple in the ocean.

Hawaiian short-tailed squid, which is a very lovely marine creature, grows up to be only thumb-sized and lives in shallow waters near the Hawaiian islands. However, the reason why these little guys are popular with scientists is not because they are cute, but because of their harmonious and delicate relationship with bacteria.

Hawaiian short-tailed squid has many ways to camouflage itself in order not to be eaten. During the day, it buries itself in the sand to rest, can also change its body color to better fit into the background, or spray ink to escape in case of danger. At night, the camouflage in the sea water depends on the help of a kind of luminous bacteria.

(Hawaiian short-tailed squid that hides itself in sand)

this bacteria is called Vibriofischeri, and they live in the light-emitting organs of squid. The blue light emitted by these bacteria looks similar to the moonlight shining into the water at night, through which the squid can eliminate the shadow caused by blocking the light from above, making it difficult for predators to see it from below. This kind of camouflage is called "luminous silhouette" (Counter-illumination). In cooperation with bacteria, the light emitting device of squid can not only glow to hide itself, but also adjust the angle and intensity of the light. At the same time, squid also provide the bacteria with nutrients such as sugars and amino acids.

(blue Hawaiian short-tailed squid)

at birth, these squid do not carry bacteria, but only a few hours after hatching, the symbiotic bacteria set up camp. There are many kinds of microbes in the surrounding sea water, but only Vibrio fluorescens can enter the light-emitting organs of squid. This is because squid produces a series of antibacterial chemicals in the light-emitting organs. This will prevent many bacteria from growing, but Vibrio fluorescens can adapt to this environment.

the partnership between squid and luminous bacteria is quite interesting, and it's definitely not as simple as bacteria coming over and glowing. For example, under the stimulation of light-emitting bacteria, the gene expression of squid undergoes a series of changes, and only when these bacteria exist can the light-emitting organs really mature. Moreover, the researchers also found that these bacteria affect the circadian rhythm of squid. The interesting thing about

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is that this deep partnership has also appeared in researchers in this field. Zoologist Margaret McFall-Ngai, who has always been obsessed with Hawaiian short-tailed squid, teamed up with microbiologist Ned Ruby to discover many secrets of cooperation between squid and bacteria. And these two people are not only partners in work, but also partners in life.

in the I Contain Multitudes video, they also show a pair of shoes painted with squid and bacteria, which feel really cute:

(consider making a couple outfit! )

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