The Ancient Back Story of the Slimiest Animal in the Sea The hagfish, known for its defensive mucus, enlarged its genome hundreds of millions of years ago. This deep-sea scavenger uses slime as a defense mechanism, expanding rapidly in water. Scientists sequenced its genome and found evidence of genome duplications, shedding light on early vertebrates. Surprisingly, the genome enlargement did not lead to a wide variety of body shapes. Further research is needed to understand the hagfish genome and its unique traits.