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As crawfish season comes to an end, a collective sigh should be heard throughout the crustacean community. Like humans, these mini-lobsters experience emotion and get stressed and anxious.

Another similarity between crawfish and humans is that both can be calmed with drugs, according to researchers.

Lead researcher Dr. Daniel Cattaert and his team from the University of Bordeaux say that the latest study is the first to show that fear and anxiety can also be felt by spineless creatures, which are considered more primitive forms of life.

For the experiment, scientists administered a series of mild shocks to crawfish before putting them into an aquarium "maze" that contained both well-lit and darkened burrows. Researchers noted that crawfish are more comfortable in darker environments.

The study revealed that the act of avoiding light was linked to higher levels of the brain chemical serotonin in crawfish. The study also revealed that injecting serotonin in crawfish also made these crustaceans anxious.

This is interesting as serotonin also significantly influences mood in people.

Like people, crawfish treated with anti-anxiety drug chlordiazepoxide (CDZ) became less nervous and were more courageous to explore brighter environments.

"Analyses of this ancestral behavior in a simple model reveal a new route to understanding anxiety and may alter our conceptions of the emotional status of invertebrates," researchers wrote in the study.

"[Our results] emphasize the ability of an invertebrate to exhibit a state that is similar to a mammalian emotion," they added.

The findings are published in the journal Science.