Canny shrimp learn to avoid invading predators

Posted on January 5, 2013

Freshwater shrimp have a strong influence on nutrient recycling and the makeup of algal and invertebrate communities.  For this reason, changes to the species balance caused by the consumption of shrimp by invasive predators have the potential to significantly alter ecosystem structure.  To a large extent, the impact of aquatic invaders will depend on the capacity of shrimp to modify their behavior to reduce their exposure to predator attack.   This ability was the subject of an Australian study using glass shrimp and mosquitofish as test species.  The glass shrimp (Paratya australiensisis) is the most common freshwater shrimp in eastern Australia, while the mosquitofish, Gambusia holbrooki, is one of the most globally ubiquitous invasive species and is a recognized threat to native fish, frogs, crustaceans and other freshwater animals.  Groups of three glass shrimp from ponds that had been devoid of fish predators for several generations were kept in 16 aquaria, where their activity patterns were monitored over a period of two weeks.  One mosquitofish was then added to eight of the tanks and the activity of all shrimp and fish was recorded over another two weeks.  Each tank contained a refuge that allowed the shrimp to avoid mosquitofish attacks.  In the first part of the experiment shrimp were active during daylight hours, but during the second period shrimp that were exposed to Gambusia showed a dramatic shift towards night-active behaviour.  Therefore it seems that crustacean species can indeed learn to improve their chances of surviving invasions of alien predators. 

Reference: Bool, J.D., Witcomb, K., Kydd, E. & Brown, C.  2011.  Learned recognition and avoidance of invasive mosquitofish by the shrimp, Paratya australiensis. Marine and Freshwater Research, 2011, 62, 1230–1236.