Photograph by Thomas Redd, My Shot

The colorful lionfish presents an attractive appearance, but its arsenal of needlelike dorsal fins is actually meant to warn others away. Too-curious humans can receive a quite painful and potentially dangerous sting from these spines. Lionfish hail from Indo-Pacific reefs but they have recently spread to other warm waters, like the Caribbean, where they are causing some ecological concern by thriving as an invasive species.