When a small number of bristlesquid were chased downstream by pursuing shrotters, where most escaped with their lives by getting themselves lost in the murky waters of the Ichthy Swamp, the brittlesquids were given the opportunity to be born. Because of this separation from their original location, they split from their ancestors instead of replacing them.
They adapted to bury themselves in the substrate of the swamp bed, where they will spend the entirety of their lives. This manifests itself in an elongated mantle, which, to move downwards, will elongate, expand outwards, contract lengthwise to pull it down, and then contract inwards, much like a worm or a clam might do. Their dens are long enough to pull their bodies down to the hood against the ground, which is too big to squeeze into the tiny hole properly without sustaining potential damage to the den's overall structure. Because of this, they have evolved small but sharp spurs on the underside of their arms where there is a lack of setae below the mantle. When threatened, they will quickly squeeze their main body down into the burrow, then curl their arms back, pulling the mantle down over their heads and exposing the spurs to their foe. To further protect their setae-covered arms, they will then tuck them beneath the mantle to be next to the body itself, leaving only the spurs exposed.
Its skin has become paler, to help reflect light. This allows them to find each other during mating season. At these times, it is the males who will leave their dens to risk life and limb to mate with a female. Once copulation has occurred, the males will attempt to make it back to their burrow or hastily attempt to construct another one should they have traveled too far from it to recall where it is located; however, many may be eaten during this time as some species will keep their eyes out for the process to occur, stirring small frenzies.