Friday, September 26, 2014

Yellow-Bellied Snails OR MORE SNAIL MAIL!!!

Ground Control to Major Emily.

Yeah, Ground Control. Go ahead.

Uhhh, you still doing science out there, Major Emily? 

Sorta, Ground Control. It's complicated.  


Well here's some snail mail. New arrivals from Georgia (Fig.1)!
Figure 1. I do declare! Southern snails! We share a love of sitting on the porch drinking mint juleps.

These snails just completed an amazing transcontinental voyage (and, boy, are their arms tired! Just kidding, they don't have arms). Like other molluscan mavens of aviation described on this blog, these guys know how to travel in style - which is to say in a plastic bag, in a cooler, in a box. These are Atlantic Oyster drills from Savannah, Georgia, which are being temporarily re-homed in quarantine in Washington State(1) while they await their opportunity to teach Science amazing things about assessing risk in new situations.

You might recall the Christmas-that-Emily-Ruined Special(2), well it turns out this is the snail I was actually talking about. When I collected this species from the invasive population here in Washington (Fig. 2), those snails stopped eating and hid when they smelled chemical cues from their injured friends - they didn't even need to smell the crab that was eating those friends. They just knew that something was wrong and beat it out of there. It turns out this response is common among invasive snails here, but not seen in native snails(3).

Figure 2. The author, ca. 2009, collecting invasive Urosalpinx cinerea from Long Island, Willapa Bay, WA.

So the question becomes, are these snail species better than our local native snail species at becoming invasive because they listen to their friends when their friends are in danger? That is, do the snails back at home, in Georgia and Massachusetts, also run for their lives when they hear their friends calling for help?  Or, did the pioneer Atlantic Oyster Drills, who left their cozy homes almost 100 years ago on a railroad car headed west to an unknown destiny, in search of a land of endless undespoiled mud to roam, act basically the same as our local native snail species, and natural selection has changed the behavior of the population.  It's possible that the snails that were, quite literally, dumped from the railroad car on arrival, were all basically clueless about the predators in Washington, but some of the snails in that group did run and hide when they heard their friends calling for help when the native predators did attack - and that those snails were the only ones that survived out of the initial emigrees. They were the only ones who could reproduce, and now we have a population where that is the default response.  

Was the invasion caused by snails that listened to their scared friends, or did it result from the invasion that we now have snails that heed the warnings of other snails?

Yellow-Bellied Snails: Invasion Drivers or Survivors?

Since no one back in the early 1900's thought to do the same experiments I have done on the source populations for our invasive snails, and because the logic of time travel makes my head hurt, I'm going to do what is called substituting space for time. If we assume that there has been relatively little change in the Georgian and Massacusettsian (?) snails in the last 100 years(4), we can compare modern east coast snails (in skinny jeans, on their iPhones) to the invasive west coast population. We would predict not only that the Washington population would be more passive-aggressive, but also that they would respond similarly to the east coast snails if running away from cries of help is an invasion driver, or they would respond differently if running away was a trait that was only helpful in the new Washingtonian waters.

Ergo the snails from Georgia, now to keep my fingers crossed that the Masshole snails will make an appearance.  

Fig. 3. Snails from native and non native populations could demonstrate a variety of hypothesized responses that may or may not be related to their native culture and geographic origin.

References and Miscellany:
(1). Don't worry folks, I've got a permit and a lot of bleach and I know how to use 'em.
(2). Specifically Act II, Scene 1.
(3). More on that at some point - it's not really ready for showtime.
(4). This really only applies to the assumption that the selection for response to injured conspecifics hasn't changed, of course there have been other changes. If there have been, for instance, predators that have invaded on the east coast (cough cough, european green crab, I'm looking at you) east coast snails might also have evolved a strong response to injured conspecifics by the same mechanism of the snails that are invasive here. Actually, now that I think about it, that's one good reason to compare snails from both Massachusetts (where the Green Crab has invaded) AND Georgia (where the green crab has not invaded)