As we saw in The Cloverfield Paradox, Cloverfield Station was experimenting with the effects of their space station on a worm colony, only to have those worms disappear.
Though there’s a chance that much like Clover and the Cloverfield Monster species, these were creatures from another universe displaced into the one shown in 10 Cloverfield Lane.
Meanwhile, in 10 Cloverfield Lane, a throwaway line about John Goodman’s Howard Stambler having a theory on “mutant space worms” turned out to hit a little too close to home.
Some were found inside of a crew member on the station, in a post-mortem dissection; while others may have mutated into the huge creatures we saw Mary Elizabeth Winstead’s Michelle face off against in the finale.