There's just one thing stopping killer shrimp from wreaking even more havoc

Mar 28, 2014 by Tommy Leung, The Conversation
Silent but deadly. Credit: Environment Agency, CC BY

Alien species become invasive when their introduction to an ecosystem ends up causing ecological disruption in their new home. Cane toads, rabbits, water hyacinth, and zebra mussels are all infamous examples. Often these creatures are introduced to get rid of "pests".

Now a "killer shrimp", Dikerogammarus villosus, has become a nuisance in Europe. But new research shows that thanks to a little parasite, the killer shrimp has caused much less havoc than it might otherwise have been capable of.

One of the theories for why some introduced species become so successful in a new region is called the "enemy release hypothesis". In their new home, introduced species run amok as they are no longer hounded by their usual foes that would otherwise keep their population in check.

Dikerogammarus villosus is an amphipod – a little, shrimp-like crustacean – from the Ponto-Caspian region that has invaded western and central Europe, and is now also found in the UK. They only grow up to a little over an inch long, but they are voracious little predators that eat everything smaller than themselves, including each other. Released from their usual predators and , the amphipod rips through the freshwater life of its new neighbourhood.

The inescapable foe

But D. villosus has not completely escaped from its past foes, according to a recent paper in the journal Parasitology. A nasty parasite (a microsporidian) called Cucumispora dikerogammari invades the 's muscles, reproduces prolifically and eventually kills it. There is some concern that this parasite can spill over into the native invertebrates . But it is also one of the few things holding back the voracious D. villosus from causing even more destruction.

There's just one thing stopping killer shrimp from wreaking even more havoc
Top: A heavily infected amphipod. Bottom: Spores of C. dikerogammari Credit: Parasitology/Wattier et al

A group of scientists from France conducted a study to look at how C. dikerogammari affects the activity levels and appetite of D. villosus. The scientists observed the behaviour of both infected and uninfected amphipods in a water-filled glass tube and noticed that amphipods at a late stage of infection that are visibly "filled to the brim" with parasite spores are actually more active than healthy amphipods or those that are not visibly parasitised because they are at a much earlier stage of the infection.

They also presented amphipods with bloodworms to see how many they ate. Both infected and uninfected D. villosus pounced on those insect larvae, but the heavily infected amphipods ate far less than the healthy ones. For some reason, this parasite seems to cause D. villosus to lose its appetite, and given this crustacean's reputation of eating everything that it can get its claws around, this may have reduced its overall ecological impact.

Yet again, another parasite has busted the myth that they are just free-loaders. But the story leaves an unanswered question, why would the parasite make its host more active before killing it?

This could just be an odd manifestation of the parasitical disease. Regardless, such behaviour is certainly a useful one for the parasite – as it depends upon cannibalism for transmission to new hosts.

Dikerogammarus villosus usually prefer to stay under a shelter and wait for potential prey to wander by. By getting their host out and about, C. dikerogammari might increase the chances that its host will either run into one of its cannibalistic buddies, or die out in the open where it can be scavenged by other amphipods.

It seems that, for the invasive killer shrimp, no matter how far you go, you can never really run away from your past.

Explore further: Baby 4: Newborn spotted with endangered Puget Sound orcas

Related Stories

Demon shrimp threaten British species

Feb 11, 2014

A species of shrimp, dubbed the 'demon shrimp,' which was previously unknown in British waters, are attacking and eating native shrimp and disrupting the food chain in some of our rivers and lakes. The problem ...

Lifestyle of a killer

Sep 06, 2012

Parasitic dinoflagellates of the genus Hematodinium are a big problem for crab, prawn and shrimp fisheries across the world. New research published in BioMed Central's open access journal Aquatic Biosystem ...

Recommended for you

Mice sing like songbirds to woo mates

39 minutes ago

Male mice sing surprisingly complex songs to seduce females, sort of like songbirds, according to a new Duke study appearing April 1 in the Frontiers of Behavioral Neuroscience.

A new crustacean species found in Galicia

1 hour ago

One reason that tourists are attracted to Galicia is for its food. The town of O Grove (Pontevedra) is well known for its Seafood Festival and the Spider Crab Festival. A group of researchers from the University ...

Ants in space find it tougher going than those on Earth

2 hours ago

(Phys.org)—The results of a study conducted to see how well ants carry out their search activities in space are in, and the team that sent them there has written and published the results in the journal ...

Rats found able to recognize pain in other rat faces

2 hours ago

(Phys.org)—A team of researchers working in Japan with affiliations to several institutions in that country, has found that lab rats are able to recognize pain in the faces of other rats and avoid them ...

Isotope study shows which urban ants love junk food

15 hours ago

Research from North Carolina State University finds that some - but not all - of the ant species on the streets of Manhattan have developed a taste for human food, offering insight into why certain ants are ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.