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Natural “Velcro” binds ant, tree in cooperation

June 29, 2010
Courtesy CNRS
and World Science staff

A­bove, A. an­drea ants are shown both wait­ing on the side­lines and at­tack­ing a wasp in the mid­dle of a leaf. Be­low, ants swarm on­to a hap­less moth in what re­search­ers said was a strug­gle that be­gan at night and con­tin­ued in­to the morn­ing. (Im­ages cour­te­sy De­jean et al., PLoS One)

A South Amer­i­can ant uses a “Vel­cro”-like prin­ci­ple to cling to a tree with which it has a sym­bi­ot­ic, or co­op­er­a­tive, rela­t­ion­ship, bi­ol­o­gists have found.

Alain De­jean of the French Na­tional Cen­ter for Sci­en­tif­ic Re­search and col­leagues stud­ied how the ant Az­teca an­dreae hangs on­to the leaves of the Ce­cro­pia ob­tusa tree.

The plant, the em­blem­at­ic tree of Guy­ana and al­so called the trum­pet tree, has de­vel­oped a sym­bi­ot­ic rela­t­ion­ship with var­i­ous ants of A. an­dreae’s ge­nus, or ev­o­lu­tion­ary group. The tree pro­vides the ants a nest­ing place in hol­low stalks and some food. The in­sects in turn guard the plant against leaf-eat­ing pests.

A. an­dreae ants in particular don’t eat from the host tree, but have in­stead de­vel­oped a hunt­ing strat­e­gy based on an elab­o­rate so­cial or­gan­iz­a­tion, the re­search­ers found. Work­ers ants line up side by side be­neath the leaf edges and wait for any prey to land, wheth­er to seek shel­ter or to munch on fo­li­age.

The sci­en­tists found that, in this po­si­tion, the ants grip firmly on­to the leaves us­ing the “Vel­cro” prin­ci­ple. The un­der­side of the leaves is downy, which con­sti­tutes the velvet-like sur­face to which the work­ers’ hook-shaped claws at­tach.

Vel­cro, a trade­mark of Vel­cro In­terna­t­ional BV, is a ma­te­ri­al con­sist­ing of two tex­tile strips, one with a velvet-like sur­face and the oth­er cov­ered with tiny hooks. The strips at­tach to each oth­er firmly but can al­so be easily torn apart by pulling side­ways, for a range of ap­pli­cat­ions in cloth­ing and else­where.  The name stems from the French “vel­ours,” mean­ing “vel­vet,” and “cro­chet,” mean­ing “hook.”

The “natur­al Vel­cro” lets A. an­drea ants sup­port up to 5,000 times their own body weight, De­jean’s team found. In one case, in­ves­ti­ga­tors watched as the ti­ny ants ganged up on and caught a huge lo­cust weigh­ing the equiv­a­lent of more than 13,000 work­er ants, or al­most 19 grams. The find­ings are pub­lished in the June 25 is­sue of the re­search jour­nal PLoS One.

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A South American ant uses a “Velcro”-like principle to cling to a tree with which it has a symbiotic, or cooperative, relationship, biologists have found. Alain Dejean of the French National Center for Scientific Research and colleagues studied how the ant Azteca andreae hangs onto the leaves of the Cecropia tree. Cecropia, the emblematic tree of Guyana also called the trumpet tree, has developed a symbiotic, or cooperative, relationship with various tree-dwelling ants of A. andreae’s genus, or evolutionary group. The tree provides the ants a nesting place in hollow stalks and some food. They in return protect the tree from leaf-eaters. Azteca andreae ants don’t feed from the nutritive bodies supplied by the host tree, but have instead developed a hunting strategy based on an elaborate social organization, the researchers found. Workers ants line up side by side beneath the leaf edges and wait for any prey to land, whether to seek shelter or to munch on foliage. The scientists found that, in this position, the ants grip firmly onto the leaves using the “Velcro” principle. The underside of the leaves is downy, which constitutes the velvet-like surface to which the workers’ hook-shaped claws attach. Velcro, a registered trademark of Velcro International BV, stems from the French “velours”, meaning “velvet,” and “crochet,” meaning “hook.” It’s a material consisting of two textile strips, one with a velvet-like surface and one with covered with small hooks. The two strips attach to each other firmly but can also be easily torn apart by pulling sideways. The analogous principle in the wild lets A. andrea ants support up to 5,000 times their own body weight, Dejean’s team found. In one case, investigators watched as the tiny ants ganged up on and caught a huge locust weighing the equivalent of more than 13,000 worker ants, or almost 19 grams. The findings are published in the June 25 issue of the research journal PLoS One.