The third race of Lings you could say.

Cuttlings are race of cephalopods that evolved from the cuddlefish.

Biology:

Biologically, they are more similar to that of Inklings then Octolings. The only differences being Cuttlings have smaller tentacles and different eyes.

Their pupils are wavy in appearance, just like their ancestors. They are capable of detecting brightness and even polarized light.

They completely lack the black mask-like structure commonly seen on Inklings and Octolings. It's considered fashionable to Cuttlings to wear makeup that mimics this black mask-like design. One of the most popular styles being the "Inkling Style".

The most unquie feature about them is their ability to change their color and even tentacle pattern and texture at will. This is most useful when in Cuttlefish form but it's common to see Cuttlings walking around with with multicolored, striped, zigzagged, and many more patterns and colors in their tentacle hair.

They are also much more resistant to ink attacks with this ability. Cuttlings' outer membrane is capable of absorbing ink of a different color and using it to hide, making them immune to that ink color. Over time it will fade out when in their Cuttlefish or humanoid form when they are out of the ink long enough, marked by the coloration flowing off their bodies and their current (main) color being underneath. However there is a drawback to this. Their own ink will deal less damage and they will be unable to refill by diving in their own color, which will remove the disguise color.

Cuttlings are capable of going into the water for a short amount of time as well. Their cells secrete a substance that protects their body from dissolving the instant they touch it. As stated before, this protection only lasts a short amount of time before they need to surface. They've been known to freak out Inklings on accident by going for short laps in the ocean.

Personality:

Compared to Inklings, Cuttlings are a lot less rebellious. They hate graffiti and have been known to clean up Inking Graffiti, much to the confusion and annoyance of those who put it there.

Cuttlings tend to be a lot more shy. They prefer to be left alone and have been known to startle easily if approached. Changing color then spraying pile of ink before hiding in it. It takes time if you are trying to befriend one as a Cuddling has to open up first. Any Inkling or Octoling who is patent with them will find themselves with a lifelong friend.

Relationships and culture:

Cuttlings and Inklings get along really well and they're trying to be peaceful with Octos. Cuttles chose to remain neutral during The Great Turf War as they were trading partners with both sides and just disliked the thought of getting involved in the first place. Eventually they were forced to side with the Inklings after an unprovoked Octoling attack on one of their major trade ports.Once the war was over the Inkling just let the Cuttlings be.

Despite having their own Turf, many Cuttlings live amongst Inklings. Inkopolis has it's fair share of Cuttlings, many of whom would be considered rebels wanting to be "Fresh" and "Hip" with the Inklings as opposed to the typical calm and collected Cuttling lifestyle.

Not many of them compete in Turf Wars. But those that do are considered a great help amongst their fellow teammates. Cuttlings tend to prefer to play more of a defensive role than an offensive role, typically by hiding near the enemy's ink and blasting them as they try to color over their own.

Cuttlings that do play Turf Wars do not take place in Splatfests. As tension between teams tends to be really intense, the Cuttlings don't want to get involved in it.

Cuttlings have developed their own distinct culture as well. It's mostly a blend of Octo and Inkling with their own elements thrown in. Cuttles tend to care less about the latest trends and are described as a lot less forgetful then Inklings. They are known for their intelligence and concern for the world around them (Such as when the Great Zapfish was stolen, many Cuttlings were extremely worried about where it had gone). Many Cuttlings tend to go on to become Doctors, Lawyers, and even Researchers.

Many Inklings see the Cuttling lifestyle as weird. A lot of the youth refer to them as Geeklings since a lot of Cuttle youth tend to dress and participate in many stereotypically geeky things such as Dungeons & Dugongs, collecting and fixing up old and out of date gear, or anything to deal with programming or computers to entertain themselves. Yet Cuttling fashion has gained a bit of a following amongst Inklings as of recently, such as the Cuttlepack (Literally just a Fanny Pack).

Octos tend to confuse Cuttlings with Inklings a lot, especially in their propaganda which inaccurately calls them an "unnaturally smart Inklings" or mistaking them for a subspecies. Cuttles find this pretty humorous.

Civilization:

Most Cuttlings hail from what used to be North America, now known as the Cuttling Turf.

Cuttle cities tend to be a lot more high tech with little graffiti. They still have issues with pollution and trash but are working on a way to control it. Many Inkling tourists are surprised with how clean everything is.