Tuesday, August 16, 2011

Science-Lust OR Giant Eunuch Unicorn Snails

Figure 1. Rad, super-charged, super-muddy student scientists,
supporting the effort to measure all of the 1.4B Batillaria in
Padilla Bay, WA.
I'm not gonna lie, I should definitely be grading student papers right now (Figure 1). I could (and will) make excuses about the fact that I want to print them out and it's a pain to do that at home, about how I need to spend half a day catching up on other things that fell by the wayside this summer (read: begging instructors to let me into full classes since I seem to have missed the memo that it was time to register), about how I just can't muster the fortitude this morning to face the creative grammar particular to student research papers. These are all real things, and, I would argue, legitimate excuses. But I think I am actually procrastinating this way in order to recharge myself with "science-lust".

I do realize I'm a late joiner on this, as I always nearly am on all things (Kittens Inspired by: Kittens), but, damn, parasitesareSOCOOL! Many of us natural history-ragers have seen Sir David Attenborough's rather cinematic treatment of parasitic fungal infections in ants and heard about the archytypal obligate mutualistm: the fig-fig wasp system. Few hearties can really keep their brains from exploding when thinking about the ecological and evolutionary machinations of host-parasite systems, let alone parasitoids (SQUEE!). But being that this is a gastropod-centric blog (and it is), we should, of course, be talking about snails. Here's my story:

This summer I started a research project on the invasive Asian Mud Snail (Batillaria attramentaria, and here's another link, go Linda Schroeder of the PNW Shell Club for taking the USGS reference photo for this snail - I KNOW her!) in Padilla Bay, WA. Researchers have made conservative estimates that as many as 1.4 billion snails might inhabit this bay, which encompasses about 5868 Ha or 14,500 acres of tideland, with densities exceeding 1,500 per square meter in some areas (O'Connor et al. 2001).  SRSLY, absurd, absurd numbers, y'all. In general, only a handful of folks are interested in these snails, because, as yet, no one has determined that they are causing that much "damage" (read: costing us money). So there's not been a lot of research on these snails. But those absurd numbers get us invasion ecologists hot and bothered, regardless of economics. So, knowing very little about these snails, as I do, I start by putting on my field ecology GoGo boots (picture to follow at some point), and walking 2 km out into the bay with a clipboard and a set of calipers (and a lot of help - I'm not gonna lie, see Figure 1).

I have been measuring snails as I walk back to shore to see whether the size of snails changes with tidal height. Imagine, if you can, my excitement when I observed this fine figure (Figure 2):
Figure 2. Snail size with distance from shore. Sorry for the
jenky use of  Excel here, I was too excited to write R code.
Also, dudes, these data are mine, so don't steal em or anything.

Okay.   I won't dwell on this, but for those of you who still have your jaw attached, those are some pretty freakin beautiful ecological data. I'm not at all ashamed of the fact that I posted it on my facebook page.  I've done several more transects, and while those data aren't as orderly, the same general pattern of increasing size with distance from shore holds (also note tiny YOY in the mid-upper range! Adorable!).

Get on with the parasites already, Emily! JEEZE! 

OK, OK...So it turns out an astounding 82% of Batillaria in Padilla Bay are infected with a castrating (!) trematode parasite (Torchin et al. 2005). I started wondering whether infection status varied with tidal height, so I emailed the afore-referenced Mark Torchin about whether he had any observations on it.  It turns out that he (and others) published an entire frickin paper in Proc. B. demonstrating that not only do the flukes castrate the snails, they also cause snails to resume somatic growth (gigantism) and cause them to migrate lower in the intertidal (Miura et al. 2006).  Well...that explains the large snails on the lower end of the transect.  

A) there are so many questions that remain! and, 
B) there are hundreds of thousands of giant (I've measured some as large as 50mm!), eunuch (parasites castrate by consuming gonadal tissue!), unicorn (come on, don't their shells look whimsical?) snails roaming Padilla Bay!

Indeed, for today, it is enough to draw my inspiration from the circus feaks of western Washington (it is pretty close to Bellingham, after all - ZING!). It seems like I have accrued enough exclamation points in this post to achieve science-lust status once again.  

Miura et al. 2006. Proc. R. Soc. B. 273:1323–1328
O'Connor et al. 2001. Padilla Bay NERR Technical Report No. 25.
Torchin et al. 2005. Biol. Inv. 7:885-894.

Tuesday, August 2, 2011

"Death by radula" OR "An introduction to predatory snails of the PNW"

Urosalpinx cinerea having their way with a Crassostrea gigas
One of the things I really enjoy about what I do is getting to talk about killer snails.  Those of us who garden are, of course, lamentably familiar with the destruction wreaked by terrestrial snails and slugs.  But, by and large, the majority of the (non-marine) folks who ask about my research are surprised to learn that snails can be voracious predators of flesh.  My favorite part of this exchange is always watching how people react to a description of death by radula, which, even without the, shall we say, vibrant descriptors and pantomime I typically provide, is actually pretty graphic.  

In the most antiseptic terms, death by radula goes as follows: Snails (and many other Mollusks) have a chitinous feeding structure called a radula, something like a tongue covered with very hard teeth that is adapted to their particular diet.  Predatory snails use this as a drilling structure.  They secrete an acid to soften the calcareous shell of bivalves, barnacles, and yes, their friends if need be, and scrape away softened shell with their radulas, until they have pierced the shell (see below). This has earned the snail depicted above the fitting common name of Oyster Drill. 
Oyster drill (Ocinebrina inornata) hole in Crassostrea gigas shell.

Then they suckouttheguts! 

There are of course, other feeding strategies for predatory snails (see the Conus genus hunt...and be astounded! Moon snails cannibalize their buddies by smothering them!  Come at me, bro!). But my point is this: reactions to this imagery can typically be categorized as either grossed out, or fired up.  No one is completely unmoved by the thought of being an oyster in your lil' shell and knowing, even limited by your relatively undeveloped nervous system, that there is a snail drilling into your shell WITH ACID, and that it will SUCK YOUR GUTS OUT when it gets through.  And there is NOTHING YOU CAN DO TO STOP IT.  

The fired up among us are my kindred spirits.  This blog aims to be a celebration of the little gems of insight on the natural world that get us all fired up, the moments of enlightenment that change the way we look at the world around us, and make us grateful that we are not oysters.

Rah Rah Radula