Flexible worms - Nematodes migrating with a surprising ease from the sea to the mainland and vice versa.
Like many major animal group, nematodes most likely arose about 530 million years ago during the Cambrian explosion. In those days animals lived in marine habitats, and there has been quite some speculation about how nematodes entered the continents. Using a ‘neutral’ gene - ‘neutral’ because it (ribosomal DNA) has nothing to do with living in the sea or on the continent - we reconstructed the relationships between major groups that harbor numerous marine species. To our surprise, we could pinpoint 16 events were marine nematodes entered the main land, and vice versa. Apparently, it is not so difficult for a nematode to adapt to a new environment. Here, it should be kept in mind that nematodes have no lungs or gills – they breathe through their skin by diffusion. Nevertheless, it was a great surprise to see that these little worms migrated so frequently from the sea to the mainland and back again!