Pheromone makes squids aggressive

February 11th, 2011 - 5:14 pm ICT by ANI  

Washington, Feb 11 (ANI): Scientists have discovered that female squid produces a pheromone that triggers immediate and dramatic fighting in male squid that come into contact with it.

The aggression-producing pheromone, believed to be the first of its kind discovered in any marine animal, belongs to a family of proteins found in vertebrates, including humans.

“The identification of this pheromone as a key component of this signaling system is highly unusual because the male squids need only to come into contact with these protein molecules to initiate the complex cascade of behaviors that we term aggressive fighting,” said Roger Hanlon, senior scientist at the Marine Biological Laboratory (MBL) and study co-author.

In field studies, the scientists observed a visual attraction by male squid to eggs laid on the sea floor followed by an escalation from calm swimming to the highest level of aggressive fighting-even in the absence of females-when they physically contacted eggs.

Seeking to identify what was triggering the behavior, Hanlon and his colleagues, conducted laboratory experiments.

They discovered a protein pheromone produced in the female reproductive tract and embedded in the outer surface of eggs. After purifying the pheromone and presenting it to male squid in the lab, they found the same extreme aggressive responses, even when the protein was “painted” translucently on a glass vial that contained squid eggs.

“The contact pheromone was incredibly resistant to degradation. It appears to remain intact for an extended period of time until the eggs are seen and contacted by male squid,” said Nagle.

Lab experiments showed that the male squid that touches the eggs first becomes aggressive faster than other males who have not yet touched the eggs. This led to dominance by the males that encounter the pheromone.

While there are multiple discoveries of pheromones that can elicit aggression in land-based animals, the scientists maintain that this discovery in squid will help them to understand the critical signaling beneath our oceans.

“Squid may have revealed a more direct way of stimulating aggression. We doubt that many researchers have thought that contact with molecules in the external world could stimulate such complex and extreme aggressive behavior,” added Hanlon

The results appeared in the journal Current Biology. (ANI)

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