Species species of the Week week #4 OR Hiphopopotamus

Hippopus hippopus

(The Horse's Hoof Clam OR 

The Strawberry Clam OR 

The Bear Paw Clam)

Figure 1. What a wacky looking clam!!
Photo Credit: Mehmet Atatur

Figure 2.  Yup, wacky from this angle too!

Right, so the radness of the shell alone (Figs 1 & 2) is pretty much enough coolness for this tautonym to stand on, but there is so much more to Hippopus hippopus (Disambiguation: Did you mean "Hiphopopotamus"?) that makes it cool. And for that we need to see a picture of it in situ, up close:

Figure 3. Open live H. hippopus, looking even wackier

Go closer...

Figure 4.  Siphon and wacky mantle tissue.
Photo Credit: Artesub.com

Closer still...

Figure 5. Extreme Close-up. Reflective proteins in mantle tissue of Tridacna
Micrograph Credit: Griffiths et al. 1992

Too close, a little too close!

Figure 6. Dinoflagellates (non-algae algae) of the genus Symbiodinium.
They live in giant clam flesh!

There!  Living right in the mantle tissues of these Giant Clams are dinoflagellates (1),  phytoplankton of the genus Symbiodinium.  The genus name kind of says it all.  These  wiggly bulbous photophiles have a symbiotic relationship with the clams whereby they use sunlight to produce carbohydrates, which the clam then eats, and in return, they get a stable habitat in which to live and drink up the sun.  Free-living dinoflagellates, like all plankton, are at the mercy of the tides and currents and can get forced down to a depth beyond which they can obtain sufficient light to photosynthesize (= bitty dinoflagellates, wasting away).  By paying a bit of rent in the form of sugar to the clam, symbiotic dinoflagellates are assured that they will not be sucked into the deep.

Ok, so that's cool enough, but not unique.  This is roughly the same symbiosis as corals and our own local Anthopleura anemones (see really, really ... really cool research at Western on climate change and symbiosis).  

But!  What I learned just this week at a talk by Alison Sweeney (2) was that not only do the clams have algae all up in their skin, but they apparently also modify their own mantle tissue feed more dinoflagellates, and thereby get more sugar.  They're farmers! The iridescence you see in the mantle (Figure 4) is generated by iridocytes, cells with organized proteins all stacked up (Figure 5).  What are the iridocytes for?  There are a number of ideas that have been considered, including protecting the dinoflagellates from exposure to too much sun, which can cause chemical stress on both dinos and clams.  

However, modelling and experiments done by Dr. Sweeney and friends indicate that proteins in iridocytes forward scatter wavelengths of light that are useful in photosynthesis, deeper into the clam than it would otherwise go.  This is good news for the dinoflagellates and the clam (more light -> more photosynthesis for more dinoflagellates -> more candy for the clams!).  However, the iridocytes backscatter  the other wavelengths (like green), so we see green iridescence. So, it's possible that the clam uses iridocytes to improve their dinoflagellate husbandry.

Dang, clam, you pretty and smart!

References and miscellany:

(1) Pedantic note about pronunciation of this word: Neigh on a decade ago, it was STRONGLY emphasized to me by Greg Teegarden who learned it from his Academic forefathers/mothers that "Dinoflagellates" is pronounced "DEE-no" NOT "DYE-no".  The former is derived from Greek meaning "rotation", referring to the transverse flagellum that causes these guys to spin, while the latter signifies the Greek word "deinos", meaning "terrible" - like Dinosaur = "terrible lizard".   It seems to me that these are spinning, but not terrible, flagellates.  

(2) Most official website I could find for Dr. Sweeney, this is from Duke where she did her Ph.D. Currently at UCSB Institute for Collaborative Biotechnologies, headed to Penn Physics this fall. She has also done lots of work on coloring and iridesence and optic stuff in cephalopods. 

Scientistas of the World Part II OR More Swoonage

This post closes the loop on my promise to write about TWO Scientistas back in October for Ada Lovelace Day.  Get off my back, man, I said I'd do it!  Just kidding, absolutely no one but me is actually concerned about whether or not I write this post.  Except maybe my reader in Russia! Google tells me that I have three views on Rah Rah Radula from Russia.  Probably it's just someone phishing for my credit card number.  They'll probably succeed, but in the meantime maybe learn something about snails and science.  SUCKERS!

Part II: Sharon Strauss and More Swoonage

So, recalling that Ada Lovelace Day is all about inspirational women in STEM fields, I'd like to call your attention to Sharon Strauss.  Now, I have a bad habit of letting my first impressions get the best of me.  I first paper-met her  when I read a review she wrote with colleagues at UC Davis about how native species evolve in response to introduced species.  This is undeniably a cool topic.  To give you just a taste of what's going on out there:

Witness the Black Snake of Australia

Figure 1. Witness! Are you Witnessing? You better be! This handsome devil,
helpfully demonstrating "gape-limited predation" is Pseudechis porphyriacus. 

The Black Snake, Pseudechis porphyriacus, is native to Australia, where it preys on anything smaller than it's head (witness Figure 1), rodents, amphibians, whathaveyou. Wait did I just say amphibians?! In Australia?! That's right, Ima talk about CANE TOADS!!!  For those of you who haven't watched the never. -ending. parade. of documentiaries. about this particular poster-child of biological invasions, cane toads were introduced to the continent-cum-island to control cane beetles in 1935. The beetles were accidentally introduced earlier and were problematic for the sugar cane growers.  Folks thought the toads (incidentally Bufo marinus) would solve their problem by eating the cane beetles.  But toads found everything else in Australia much tastier.  So cane toads became super abundant without solving the beetle problem.  In addition to eating everything except what they were supposed to, they also killed native things that ate them, because they secrete a toxin (witness Figure 2) when they are threatened or have road rage (it's ALL about inducible defenses people!).

Figure 2. Oh gross, that white stuff is bufotoxin and this toad is MAD!

So black snakes were eating cane toads and dying from actual food poisoning. But!...BUT! It appears that in approximately 23 generations of snakitude, this species has not only evolved increased resistance to the toxin (Phillips and Shine 2006), they also have evolved smaller heads (Phillips and Shine 2004).  What?! Smaller heads?! That's dumb.  No, smaller heads for a gape-limited predator means you can only eat smaller toads.  Smaller toads make less toxin.  Pinhead snakes eating small toads live to pass on their pinhead genes to the next pinhead generation. EVOLUTION: WIN! 

Anyway, that's way cool, but let's get back to the point

Shocking Upshot: I got really excited about this paper and this concept. Evolution happens so fast, and humans can cause it and we can see the effects!  So, naturally, the author was elevated to Science Goddess status.  But my hasty opinion of Sharon Strauss was formed on one paper only.  Last spring, as part of an ecology seminar, I reviewed and presented on a larger portion of her corpus, and you can imagine how much higher Sharon rocketed in my esteem (hint: way higher) when I realized how broad her research was (hint: pretty, pretty broad, witness the breadth of Figure 3).

Figure 3. Portrait of Sharon Y. Strauss and Friend.

In addition, and I wish ESA hadn't removed or archived this information because it will not have the same impact if I just tell you about it, she wrote this great piece in a profile about the joy of doing science that serves our curiosity.  Or at least that was what I took away from it, so it's entirely possible I'm getting this wrong or projecting.  I'm pretty sure it was something along those lines anyway.  My point is that my perception of Sharon Strauss is that she approaches not only the content of science thoughtfully, as demonstrated by the strength of her research program, but also the act of doing science, the living of a scientific life, of training more scientists.  If that sounds a bit grandiose, that's because it's how that makes me feel.  This is, I think, how we all start out, as scientists and/or students, but something we quickly lose sight of when we get bogged down in logistics of funding and politics of publication.  Or even before then when we have to cram so much knowledge into our heads because we are studying for qualifying exams and trying to remember why we thought this was a good idea in the first place and what do you with all this information that you don't have a context in which to place and didn't I learn all this before and why don't I remember it, it's a good thing I'm learning it now because I'll definitely remember it this time NO I'll never remember it it's too much and I don't even know what they're going to ask me I will definitely embarrass myself horribly in front of my committee and my life will be OVER!


...


OK. So that happened. Sorry.


Like many other passions one turns into a career, you can at least imagine how one might lose track of why one does Science when one is panicked about doing Science very well.  For me, Sharon Strauss was a timely reminder about big-picture thinking.  Inspirational scientists (and all scientists for that matter) aren't only about good science - lots of people do good science.  They are about doing good science with grace and generosity.  

Scientistas of the World: Part I OR Daydreams of a Graduate Student

So, my brother sent me some homework (thanks, man).  Today is evidently Ada Lovelace Day, on which day, we are encouraged to write something public about a woman in a STEM career (science, techmology, engineering, and math, or maths if, like the site, you're British)  who has provided us with some amount of inspriation or role-model-ship-ness-itude.  I'm not thrilled about having "homework", but without even meaning to think about it, two scientistas (I thought I was being cute and trendy using the -ista, but evidently that's actually the Italian word for a lady scientist, foiled again by romance languages) just popped into my head, and talking about their work would provide a framework for things rad and radula alike!

Part I: 

Nancy Schoeppner & The Ecology of Awesomeness

I sure don't know Nancy Schoeppner at all.  She really flies under the internet radar, this is literally the only actual information I could find on her.  I only paper-know her, as in I've read a handful of what I'm guessing is her PhD research with Rick Relyea at the University of Pittsburgh.  But, in addition to be an EXCELLENT science communicator (I totally heart reading her papers!) and experimental biologist, her work has really shaped some of my, hitherto undescribed, thinking about how prey decide whether or not to be terrified.  There are various names for this sub-discipline of Ecology: Risk-Assessment, Inducible Defenses, the Ecology of Fear (Mwahhahahahaha! It is October after all).  

The quick and dirty is this: Hark back unto my first blog post where I described the terror of being an oysters and knowing a predatory snail was coming for you, grinding a hole into your shell, hell-bent on suckingyourgutsout!  In that moment, that oyster can't really do anything about the snail, except hope he gets distracted by a pretty lady snail on an adjacent oyster and forgets about his hunger on his libidinous quest to pass his genes on (somewhat like terrestrial snails).  But some organisms can tell when they're in danger and do something about it - even plants, I kid you not!  Certain organisms can grow helmets and put spikes on their necks to make it harder for predators to eat them (so goth!), they can try to grow faster so that they get too big to be eaten by predators, or, well, they can run away and hide.  These are called inducible defenses.  Trying to figure out how these guys tell when they're in danger is, it turns out, really fun [for Emily].

Nancy's work has tested a bunch of hypotheses about risk assessment, and I think they are applicable to human decision-making in times of potential threat by carnivorous preadators (i.e., zombies, flesh-eating bacteria, Orca: the Killer Whale, etc.).  So here is Nancy Schoeppner's:  

3 Risk-Assessment Rules to Live and Die By

1.  If you can smell your family being eaten, there's a pretty good chance you also are in danger of being eaten, and you should do something about it.  

If you can smell your friends being eaten, there's still a good chance you're in danger, but maybe don't freak out so much.  If all you can smell is some folks you don't even really know and have never met and who have a totally different diet and culture from you getting eaten - no biggie! It's not really your problem, becuase those other prey (suckers!) are so unlike you, the predator probably doesn't even recognize you as potential food!  (NB: It's possible that this rule also guides US cultural attitudes and policy decisions)

2.  If there is a large cost to defending yourself, you should def. wait until you have good information that there is a serious, serious risk.  

Tadpoles in Schoeppner's experiments only changed their growth patterns (very pricey, energetically, and also non-reversible, so they're screwed with their permanent giant tails if they're wrong!) when they smelled predators consuming AND digesting friends/family, but they changed their behavior (who cares?! You can just come out from your hiding space when you realize your friends were punking you, and all you lose is your dignity!) in response to less threatening smells.  

3.  Do the math, dummy. 

If there's only one shark in the water (Fig. 1) but 500 tasty fat people, simmer down!  Probably that shark will rip off somebody else's leg (phew!) and then realize humans taste like diet soda and a bitterness that can only be acquired from a lifetime of regrets.  If the shark attacks randomly, the probability you will lose your leg is 1 in 500.  But if you all panic, you miss valuable wave time, and increase the probability that you will get crushed by the 499 panicking morons on their way to shore.  If, however, there are 499 sharks, and 500 people, the probability that you will leave the beach with all 4 limbs is 1 in 500, and so taking the chance of getting stampeded by your fellow prey is probably still a safe bet.

Fig. 1 Do not run from this shark - it probably won't rip your 

leg off because, no offense meant, but it would probably rather 

eat a brownie sundae. I put this picture in here because this post
is long and boring.

There are most certainly more rules, but these are the best supported.  I hope to add my own rules some day.  For instance, if you're on vacation, how can you tell whether that Italian man is ogling you because he's hungry, or because he likes the cut of your minigonna?  Are there threat-signals that transcend international boundaries?

My point is that plants and animals seem to be very good at telling when they are safe and when they should hit the deck, and can optimize these situations to make sure that they will live long enough to make many, many babies.  Even cooler, they do this all without actuarial tables, the Central Intelligence Agency, night-vision goggles (well some of them do have pretty good night vision), or even very sophistocated sensory systems.  I have really benefitted from Nancy's clear thinking and writing, and her thorough experimental technique - Swoon.  I'd love to write a review paper with her some day - but these are merely the silly daydreams of a graduate student putting off other work...

Nancy Schoeppner - Selected Publications (in no detectible order):
1. Schoeppner & Relyea (2008) Oecologia. Detecting small environmental differences: risk-response curves for predator-induced behavior and morphology. 154:743-754.
2. Schoeppner & Relyea (2009) Functional Ecology. Interpreting the smells of predation: how alarm cues and kairomones induce different prey defences. 23: 1114-1121.
3. Schoeppner & Relyea (2009) Copeia. When Should Prey Respond to Consumed Heterospecifics? Testing Hypotheses of Perceived Risk. 1: 190-194
4. Schoeppner & Relyea (2005) Ecology Letters. Damage, digestion, and defence: the roles of alarm cues and kairomones for inducing prey defences. 8:505-512.