Nature hasn't left the catfish declawed, so to speak.

Some catfish species have been known to be venomous—including a few dangerous enough to kill a human. But scientists knew little about how common venomous catfish are or how the fish produce and deliver their venom.

Turns out, the ability is more widespread than anyone realized—extending to about half of the more than 3,000 known catfish species, according to a new report.

For the study, biologist Jeremy Wright studied the venom and microscopic tissue structures of 158 catfish species. Based on known relationships among those species, the University of Michigan graduate student concluded that at least 1,250 to 1,625 catfish species are likely venomous.

The explosion in known venomous catfish species, however, doesn't mean