Shell Shocked?

Scientists have revealed that the European shore crab (Carcinus maenas), a close relative of crab species that are commonly fished for food, reacts positively to electric shocks and tries to avoid them. However, this is not the first study that has obtained such research, as previous research has also indicated that prawns and hermit crabs react to painful stimuli.

Image Courtesy of foxypar4

Unfortunately, such studies are often very hard to quantify since the perception of pain is a very subjective response – especially when it comes to invertebrates such as crabs that are not exactly as expressive as mammals.

In the study European shore crabs were used, which is a littoral species of crab that lives in coasts and takes shelter under rocks during the day to avoid being preyed upon. Ninety crabs were placed in a bright area and given the option to take shelter in two dark areas. Once these animals selected their refuge, half were given an electric shock in the first shelter they chose. The shocked crabs were placed in the tank again and appeared to ignore the initial shock. They were shocked again, but this time the painful experience remained imprinted in their minds and affected their future behaviour. The change in shelter selection was found to be significant since the crabs were leaving the dark sheltered area which they are very accustomed to. The crabs were then placed into the tank a further eight times, and they continually avoided the shelter in which they were shocked.

This study was reviewed by several scientists who indicated that it was conducted in a rigorous and scientifically meticulous way. As such, it sheds light on how animals learn from experience through pain and other reflex reactions, thereby affecting future choices. Such findings could have considerable implications on how these animals are treated in the food and aquaculture industries.

As humans we like to anthropomorphise animals, case in point with Sebastian the Crab in Little Mermaid. It appears that these tendencies may have some scientific significance after all.

By Antoine Borg Micallef