GALVESTON, Texas - Just in time for Halloween, Texas Parks and Wildlife spotted a really spooky-looking parasite inside a fish's mouth. It is truly the stuff of nightmares.

"Inside this Atlantic Croaker’s mouth is a parasitic isopod called a tongue-eating louse. This parasite detaches the fish’s tongue, attaches itself to the fish’s mouth, and becomes its tongue. The parasite then feeds on the fish’s mucus. It also happens to be the only known case where a parasite functionally replaces a host’s organ," said Texas Parks and Wildlife.

According to Wikipedia, the species starts as a juvenile in a short, free-living stage in the water, then attach themselves to the gills of a fish and become males. As they mature, they become females after mating on the gills.

If no female is present, a male can turn into a female. The female then makes her way to the fish's mouth, where she uses her front claws to attach to the fish's tongue.

Thankfully, it doesn't affect humans or even kill the fish.