Explore by Subject
Get 4 extra free issues and unlimited free access to NewScientist.com
New Scientist is now partnered with Approved Index. Visit the site to get free quotes from website designers and a range of web, IT and marketing services in the UK.
Living World

Fossilised shrimp show earliest group behaviour

  • 19:00 09 October 2008
  • NewScientist.com news service
  • Ewen Callaway
Printable versionEmail to a friendRSS FeedSyndicate
The fossilised chains of up to 20 crustaceans linked head-to-toe is the earliest record of any collective animal behaviour (Image: Science)
The fossilised chains of up to 20 crustaceans linked head-to-toe is the earliest record of any collective animal behaviour (Image: Science)

The conga was the world's first dance, it seems. A newly discovered caravan of crustaceans from half a billion years ago shows that group behaviour evolved not long after animals themselves.

Palaeontologists led by Hou Xian-Guang, of Yunnan University, China, discovered fossilised chains of up to 20 crustaceans linked head-to-toe, the earliest record of any collective animal behaviour and perhaps an adaptation to a migratory ocean lifestyle.

"It's showing that, 525 million years ago, we've got really quite sophisticated and potentially complex interaction between different animals," says Derek Siveter, of the University of Oxford, who analysed the fossil along with colleagues at the University of Leicester, UK.

They concluded that the undulating procession of ancient arthropods, each about 2 centimetres long, represents more than a quirk of fossilisation. Though none of their arms, legs or antennae survived a half billion years in stone, the animals probably interlocked appendages to stay together.

"We hypothesise that the chain was in the water column and it met its demise by whatever reason or forces, then it sunk to the bottom," he says.

Modern creatures called tunicates, or sea squirts, form long chains to boost mating opportunities, but Siveter doubts that his crustaceans engaged in a carnal dance because no modern crustaceans show this behaviour. Group feeding is off the table, too, because each animal's mouth appears blocked by its neighbour's tail.

"The simplest explanation for this is that it is some kind of collective behaviour coming together for migration, perhaps associated with defence in numbers," he says.

Nigel Hughes, a palaeobiologist at the University of California, Riverside, agrees that the parade represents more than the death throes of ancient arthropods. Rather, the fossils provide "snapshot scenes of 'normal' life" in the Cambrian, he says.

"Finding an example of collective behaviour so long ago is really eye opening to us," says Iain Couzin, a biologist at Princeton University. He and colleagues are now creating computer models to understand the evolution of group action, which seems to arise often and with little individual complexity needed.

"Collective behaviour is all around us and it's also within us, the function of cells within in the body is a form of collective behaviour."

Journal reference: Science (DOI: 10.1126/science.1162794)

Evolution – Learn more about the struggle to survive in our comprehensive special report.

Comment subject
No HTML except lower case italic tags or lower case bold tags, please:
<i> or <b>
Your name
Your email

We need your email in case we need to contact you about the comment. We will not use it for any other purpose.

There are 3 comments on 1 page

Math Of Collective Behavior

By Gregorio Kelly

Thu Oct 09 19:45:44 BST 2008

There is an equation in mathematical biology that describes the result of this sort of collective behavior in terms of metabolic rate of the overall biomass, made up of individuals. This equation explains what is behind quorum sensing in bacteria, and models biological organization as essentially an energetic phenomenon. The equation accounts for motor behavior where metabolic rate of the constituents is not enough for that behavior, but their joining together results in the larger resulting biomass having a greater metabolic rate than any individuals. This is seen also in nematodes where, by joining together, they can squirm to another location where they again disintegrate. The math is even applicable to social organization of human beings in which the body politic is based upon the division of labor and the use of money as a form of energy currency. Not surprisingly, this model advocates confederation rather than federation. The math is essentially MR (metabolic rate in watts) = W (organic biomass in grams) raised to the power (4ME-1)/4ME, where ME is a ratio of amperes of reduction to amperes of oxidation. ME ties W to the energetics of the environment.


Shrimp C0lumns. . .

By Poppa

Fri Oct 10 03:33:37 BST 2008

No modern crustaceans exhibit this trait? Maybe not perfectly, but i recall a nature film called "march of the spiney lobster" that documented them migrating in a broken chain...


Shrimp C0lumns. . .

By Ewen Callaway

Fri Oct 10 04:17:00 BST 2008

Sorry, I meant to suggest that chain hermaphroditism isn't know to occur in modern crustaceans.

Thanks for reading.


There are 3 comments on 1 page

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

If you are having a technical problem posting a comment, please contact technical support.

Cover of latest issue of New Scientist magazine
  • For exclusive news and expert analysis every week subscribe to New Scientist Print Edition
  • For what's in New Scientist magazine this week see contents
  • Search all stories
  • Contact us about this story
  • Sign up for our free newsletter
Subscribe to New Scientist magazine