Picky Eaters
Native urchins don't care for invasive seaweeds
Turns out those prickly sea urchins can be pretty picky eaters. An experiment aimed at seeing whether native urchins would chow down on alien seaweeds that are invading the Mediterranean has produced distasteful results, according to a new study.
The invasive seaweeds – known to scientists as Lophocladia lallemandii and Caulerpa racemosa – are having a “grave” effect on the seabed, a Spanish research team reports in Biological Invasions. Both have enemies that help keep them in check in their native ranges, but so far they’ve run rampant in their new homes – and the hunt for solutions is on.
To see if a native urchin named Paracentrotus lividus might help, the researchers placed cages brimming with the plant eaters into several kinds of habitat, including areas where the invasive seaweeds had barely gained a roothold, and places where they had completely overrun native marine plants. Then, they waited 7 months, and came back to see what was left.
Much to their dismay, “the sea urchins only controlled the expansion of C. racemosa in places where the invasion was still at a very early stage,” says Emma Cebrián of the University of Girona, the lead author of the study. In the case of L. lallemandii, the urchins were able to limit the seasonal spread of the seaweed – but only because they ate some native seaweeds which provide a growing platform for the invader.
“The sea urchins do not consume the invasive species according to their availability,” Cebrián says. Like all true gourmands, “they have preferences.” – David Malakoff | July 17, 2011
Source: Cebrián, Emma; Ballesteros, Enric; Linares, Cristina; Tomas, Fiona. (2011). “Do native herbivores provide resistance to Mediterranean marine bioinvasions? A seaweed example.” Biological Invasions. DOI: 10.1007/s10530-010-9898-1
Image Enrique Balesteros
