A depiction of a tardigrade
The tardigrade was a docile micro-animal that lived in the waters of Earth. It was capable of surviving both extreme heat and sub-freezing temperatures. The tardigrade was able to incorporate foreign DNA in its genome through horizontal gene transfer. (DIS: "The Butcher's Knife Cares Not for the Lamb's Cry", "Choose Your Pain")
Michael with her stuffed tardigrade
When Michael Burnham was a little girl still living with her biological parents, she slept with a stuffed animal resembling a tardigrade. (ST: "The Girl Who Made the Stars")
The organism nicknamed "Ripper" shared some natural traits with the tardigrade, and was described as its cousin. Because of this, that species was informally also called a tardigrade. (DIS: "The Butcher's Knife Cares Not for the Lamb's Cry", "Choose Your Pain"; ST: "Ephraim and Dot")