A BTC pairing. It was on the LTC market until they shut the whole LTC and Doge market down. Currently at 6 sats.
If I had to guess, Cryptopia is moving over active pairs that were on their LTC markets and pairing them on the BTC markets, and anything less than 1 sat just starts there.
There is a lot of volume currently, probably people just looking to pick up momentum and cheap coins.