Why the "Thumb Splitter" Is a Concern. Known for their aggression, Japanese mantis shrimp have earned their ominous nickname ...

The invasive species, nicknamed “the thumb splitter” is also known to make a “rumbling growl sound,” officials said.

Getty Images/iStockphoto Government officials in New Zealand are investigating how an aggressive species known as “the thumb splitter” ended up in the country’s northern coastal waters.