From 2speccers2tools wiki

Carl decided to become colonial and work together, their hands are now more mitten-like to be more cold resistant, but importantly colonies of Charles (within individual cells being known as Charlie) now contract and expand in rapid fashion, allowing movement via partial contraction, but when all members contract and expand their connections rapidly it produces heat, Charles colonies tend to gather in numbers and thus work together to create puddles, both securing food in the form of Carl but also allowing them to form a more suitable habitat for themselves and other microorganisms in general. Of course these puddles tend to be frozen over at the surface upon getting deep enough and their depth is generally controlled well enough by the slow descent of the bottom, but they still tend to hold thriving ecosystems from the heat of the Charles while also being protected from cold dooms.