"People have barely looked at this, and never before in the ocean," said Hechinger.
To answer their question, the researchers studied Kellet's whelk, a large marine snail whose historical biogeographical range starts at mid-Baja California waters in the south to Point Conception in the north. For the last couple of decades, due to the gradual warming of the ocean, the whelks have been moving their boundaries north into what used to be cooler waters. Now they can be found as far north as Monterey.
The whelks are important players in kelp forest food webs. The whelks are also a delicacy and there is a growing appetite for them in southern California. Despite this importance, there have been no previous studies of parasites or infectious disease in the whelks, much less a study examining whether they have escaped parasites in their expanded range.
However, according to the researchers' parasitological examination of whelks throughout their historical and expanded ranges, those living beyond their historic Point Conception boundary have neither the amount nor the diversity of parasites that infect their southern counterparts, despite the relative proximity of their historical range.
The researchers suspect that the northern whelks have escaped their parasites for several reasons. One factor, said Hechinger, is that the southern California whelks do not crawl around much. "It's not as if infected snails are going to move miles, wander around Point Conception, and bring their parasites to the expanded range," he said.
The whelks that are now found north of the boundary are ones that dispersed into the area during their planktonic larval stage. These juvenile stages do not serve as hosts for the parasites that infect juvenile and adult whelks. "So we know that the northern populations 'started clean,'" explained Hechinger. Those whelks would be free of the parasites they would acquire in the so
|Contact: Sonia Fernandez|
University of California - Santa Barbara