Scientists stumble on world’s first vegetarian spider

October 13th, 2009 - 2:58 pm ICT by IANS  

Washington, Oct 13 (IANS) Some 40,000 existing spider species are thought to be strict predators that feed on insects or other animals. Now, scientists have stumbled on what may be the world’s first vegetarian spider that feeds on plants.
The research, led by Christopher Meehan of Villanova University and Eric Olson of Brandeis University, has revealed the extraordinary ecology and behaviour in a small specimen known as Bagheera kiplingi, found throughout much of Central America and southern Mexico.

The spider inhabits several species of acacia shrubs involved in a co-evolutionary mutualism with certain ants.

The ants fiercely guard the plants against most would-be herbivores, while the acacias provide both housing for the ants via swollen, hollow spines and food in the form of nectar (excreted from glands at the base of each leaf) and specialised leaf tips known as Beltian bodies.

The Bagheera spiders are “cheaters” in the ant-acacia system, stealing and eating both nectar and - most remarkably - Beltian bodies without helping to defend the plant.

The spiders get the job done by avoiding patrolling acacia-ants, relying on excellent eyesight, agility, and cognitive skills.

How do the spiders get around the ants that are supposed to be guarding the acacias and

gobbling up the Beltian bodies themselves?

First, Meehan said, the spiders have what might be thought of as sheer wit. “Jumping spiders in general possess incredibly advanced sensory-cognitive skills and eight-legged agility, and Bagheera is no exception,” he said.

“Individuals employ diverse, situation-specific strategies to evade ants, and the ants simply cannot catch them.”

The spiders also seem to build their webs in less attractive plant “real estate” and to actively defend their nests against ant invaders.

Finally, Meehan added, the spiders might actually mimic the ants. Young spiders in particular look a lot like and seem to act like ants, one reason they have perhaps flown under the radar of scientists for so long despite intensive study of the ants and acacias.

The research appeared in the Oct 13 issue of Current Biology.

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