Yes. As if invasive plants weren't enough of a problem, there are invasive animals, too. Most of them haven't made it here . . . yet . . . but it's probably just a matter of time. They travel the same way the plants do - clinging to boats and trailers, in bilges and live wells, on boots, waders, fishing tackle, scuba gear, aquariums, etc. . . . The scariest might be the zebra muscle, which has been found in fresh water as well as the ocean. There's lots of good information on invasive animals in MCIAP's Field Guide to Invasive Aquatic Plants (find the link to the field guide about halfway down the page, then look near the back of the book, under "Additional Information / Other Invaders" - page 115, or thereabouts.)
There's one invasive animal that's already in Panther Pond, the Chinese Mystery Snail, those big brown snails you've probably been stepping on when you go swimming.
Oh, and more recently, there's concern about the rusty crayfish. It's not in Panther - yet - but it's been found in other Maine lakes.