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<\/div>The enormous mouth of a tiny nematode worm<\/p>\n
Sara Wighard and Ralf Sommer \/ Max Planck Institute for Biology Tubingen<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Tiny soil worms called nematodes usually feast on bacteria or algae, and have tiny mouths to suit their diet. But give a baby nematode some fungus and its mouth can as much as double in size \u2013 giving it the ability to cannibalise its companions.<\/p>\n
That is what Ralf Sommer<\/a> at the Max Planck Institute for Biology in T\u00fcbingen, Germany, and his colleagues found when studying the development of the predatory soil nematode worm Allodiplogaster sudhausi<\/em>. When the young worms were raised on Penicillium<\/em> fungus<\/a> and cheese, some of them grew up into huge-mouthed cannibals<\/a>. \u201cWe were blown away,\u201d he says.<\/p>\n The team knew of other mouth shapes found in this species that arise from different diets \u2013 nematodes that feed on bacteria have narrow mouths and those that eat a nematode species much smaller than themselves have mouths that are a bit wider. But this extreme variant, which the researchers dubbed the \u201cteratostomatous\u201d or Te morph, hadn\u2019t been documented before.<\/p>\n <\/p>\n When Sommer and his colleagues investigated the genetics underlying these different mouth shapes, they discovered that all three were controlled by the same sulfatase gene. But its activity only seems to result in a monstrous, gaping maw in A. sudhausi<\/em>. The species\u2019 full set of genetic instructions was duplicated very recently in its evolution, says Sommer, so it is possible that doubling of gene pairs facilitated the origins of the nematode\u2019s enormous mouth.<\/p>\n A fungi diet is low in nutrients, and the team found more Te morphs in high-density conditions, so the researchers think the Te morph and accompanying cannibalistic habit could have evolved as a response to the stresses of starvation and crowding.<\/p>\n Nicholas Levis<\/a> at Indiana University notes that we see a similar phenomenon in some other species. For instance, the tadpoles of spadefoot toads and some salamanders can develop into cannibalistic carnivores depending on environmental conditions, says Levis.<\/p>\n But even in those instances, the animals often avoid eating their kin. The Te nematodes don\u2019t discriminate and will devour genetically identical neighbours<\/a> \u2013 a \u201cstriking finding\u201d, says Levis, that might point to the developmental strategy being \u201ctruly desperate\u201d.<\/p>\n \u201cThe discovery\u2026 makes me wonder how much more diversity there is in nature than what we see,\u201d says Levis. \u201cHow many other hidden \u2018monsters\u2019 are out there waiting to be found under the right environmental conditions?\u201d<\/p>\n Topics:<\/p>\n<\/section><\/div>\n