Forget the killer tomatoes. Don’t stress about the zombie apocalypse. Turns out you should be worried about shrimp. Yes, the Dikerogammarus villosus, aka killer shrimp, to be exact.
This species makes its home in the area around the Black and Caspian Seas. For the geographically challenged, that includes such places as Romania, Turkey, Russia, Iran, and Kazakhstan. The Black and Caspian Seas have low salinity levels that are perfect for these creatures. They make their way out of their region and into new waters via the ballast on merchant ships. When the ships fill their ballast for the voyage, the water they take in includes these amphipod crustaceans.
The killer shrimp have already spread through central and western Europe by way of the Danube and Rhine waterways. The shrimp, which lay nearly 200 eggs per clutch and can reproduce year round, hit Great Britain about five years ago. They entered the fresh waters of Great Britain through the ballast water required by the ships.
The ships need this ballast water to balance their load while underway. Upon reaching their freshwater destinations, the ballast water is dumped – along with the murderous shrimp. The problem? In addition to breeding rapidly, these shrimp kill an alarming variety of native species – and they don’t even kill their prey so they can eat. They simply kill their prey.
As you can imagine, an aggressive alien species without anything to keep it in check can easily cause huge changes in the interrelationships between the species in that habitat. These changes are rarely positive, since they include the destruction of native species through the introduction of the invasive species.
Next up for the Dikerogammarus villosus: setting its sights on the Great Lakes-St. Lawrence River Basin of the US and Canada. Already feeling the negative impact of a number of non-native invasive species, protective regulations were quickly passed to protect this region. Thus far, the regulations have been a success and no new species have been introduced into these waters since 2006.
The regulations are simple but effective: Freshwater ballast must be discharged while the vessel is in salt water — before entering the fresh waters that make an ideal home for these shrimp — and refilled with salt water. This leaves the shrimp to die in the hostile environment of water with salinity levels beyond the shrimp’s norm.
The problem is that it may still be possible for these shrimp to come along for the ride by being carried in equipment onboard the ships. It’s also possible they could enter rivers like the Mississippi and find that the rising temperatures in the Great Lakes, brought about by climate change, make it possible for the shrimp to breach the Great Lakes from the south – through the canal that connects the Mississippi to the lakes.
This threat may not have the allure of killer tomatoes or zombies, but it is a threat that is far more real. And really really creepy.