Friday, July 6, 2012

Tiny bugs have own personalities despite being clones, scientists say

Ti­ny green in­sects known as pea aphids have in­di­vid­ual be­hav­ior pat­terns, or “per­sonal­i­ties,” de­spite be­ing clones of one an­oth­er, sci­en­tists say. The re­search­ers found dif­fer­ences in the way each in­di­vid­ual re­sponds to a threat. The study was part of a “bur­geon­ing” of sci­en­tif­ic in­ter­est in an­i­mal per­son­al­ity varia­t­ion, not­ed the in­ves­ti­ga­tors, with the Uni­vers­ity of Os­nabrueck, Ger­ma­ny. But de­spite this trend, they added, few stud­ies have been done on in­ver­te­brates, or sim­ple an­i­mals with­out back­bones. Stud­ies on “clonal in­ver­te­brates,” which are all ge­net­ic­ally iden­ti­cal and would thus be ex­pected to show lim­it­ed dif­fer­ences in be­hav­ior, are “nonex­is­ten­t,” they added, re­port­ing their find­ings in the March 1 on­line is­sue of the jour­nal De­vel­op­men­tal Psy­cho­bi­ol­ogy. “This is sur­pris­ing giv­en the ob­vi­ous ad­van­tages of us­ing in­ver­te­brates/clones to tack­le the cru­cial ques­tion why such con­sist­ent be­hav­ioral dif­fer­ences ex­ist,” they went on. Per­son­al­ity dif­fer­ences not at­trib­ut­a­ble to genes are gen­er­ally pre­sumed to be due to the en­vi­ron­ment in which an or­gan­ism formed, though there is al­so a grow­ing ap­precia­t­ion of epige­net­ic fac­tors—chem­ical dif­fer­ences that are not ge­net­ic, but that in­flu­ence gene ac­ti­vity. Pea aphids, sci­entifically named Acyr­tho­si­phon pi­sum, are pale little in­sects ty­pi­cally less than a sixth of an inch (half a cen­ti­me­ter) long that feed on pea plants and their rel­a­tives. A clus­ter of aphids in­fest­ing a giv­en plant is typ­ic­ally a ge­net­ic­ally iden­ti­cal, or clonal, group pro­duced by one moth­er with­out sex, al­though aphids can al­so re­pro­duce sex­u­ally at cer­tain phases. When a pea aphid is threat­ened by a preda­tor—of which the spe­cies has sev­er­al in­clud­ing wasps and grub­s—it gives off a chem­i­cal alarm sig­nal that alerts near­by aphids. They may re­spond in sev­er­al ways: they can walk away, drop off the plant or seem­ingly ig­nore the sig­nal. The re­search­ers, Wiebke Schuett and col­leagues, found that pea aphids can be di­vid­ed in­to one of three cat­e­gories: con­sist­ent “drop­pers,” con­sist­ent “non-droppers,” and some that be­have un­pre­dict­a­bly.
In ex­pe­ri­ments, “ma­nipula­t­ions of early en­vi­ron­men­tal con­di­tions had lit­tle qual­i­ta­tive im­pact on such pat­terns,” the re­search­ers wrote. Al­though the rea­sons for the dif­fer­ences are un­clear, the find­ings may be im­por­tant for fu­ture stud­ies of per­son­al­ity varia­t­ion and its ev­o­lu­tion­ary and ec­o­log­i­cal con­se­quenc­es, they added. Re­search­ers seek to un­der­stand how an­i­mals de­vel­op dif­fer­ent “per­sonal­i­ties” in part be­cause they want to un­der­stand how hu­mans do so. An­i­mals are used as mod­el or­gan­isms be­cause they are of­ten sim­pler and eas­i­er to ex­pe­ri­ment on. For in­stance, an­i­mals may be bred dif­fer­ently to ex­am­ine re­sult­ing dif­fer­ences in be­hav­ior, and the early life en­vi­ron­ment of a test an­i­mal can be con­trolled and ex­am­ined. Stud­ies have found that 20 to 50 per­cent of the varia­t­ion in an­i­mal per­son­al­ity traits is ge­net­ic, ac­cord­ing to re­search­ers with the Neth­er­lands In­sti­tute of Ecol­o­gy and the Max Planck In­sti­tute for Or­nith­ol­o­gy in Ger­ma­ny, who re­viewed the sub­ject for the De­cem­ber is­sue of the jour­nal Phil­o­soph­i­cal Trans­ac­tions of the Roy­al So­ci­e­ty B. “De­vel­op­ment and learn­ing” dom­i­nate the rest of this varia­t­ion, they added. But “one of the main ques­tions that still re­mains un­re­solved is why varia­t­ion in per­son­al­ity ex­ists and how this is main­tained… Mo­lec­u­lar ge­net­ic re­search on an­i­mal per­son­al­ity is still in its in­fan­cy.”

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