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ScienceShot: Spit It Out!

14 June 2012 12:00 pm
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Michal Samuni-Blank/Technion-Israel Institute of Technology

They won't win any points from Miss Manners, but seed-spitting rodents in Israel's Negev Desert avoid becoming victims of chemical warfare while sowing a new generation of a Middle Eastern desert plant. The 4-millimeter-wide berries of a plant called taily weed (Ochradenus baccatus, top left) are laced with harmless molecules that, when combined, produce a mustard oil bomb. Cracking open the berry's seeds releases the enzyme myrosinase, which mixes with compounds called glucosinolates in the flesh to produce the toxic brew. Field observations demonstrated that two species of spiny mice (Acomys cahirinus, top right, and Acomys russatus) and the bushy-tailed jird (Sekeetamys calurus) spit out intact seeds when eating the berries. When scientists deactivated the "bombs" in the lab by neutralizing myrosinase, spiny mice ate 80% of the seeds compared with 27% from active bombs. Discarded seeds had double the germination rates as seeds left in the berries, the team reports online today in Current Biology. The plant's chemical defense has thus turned a seed consumer into a disperser, demonstrating that bad manners sometimes lead to good things.

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