Hey, where's that shell going?

Have you ever been beach combing, spot a lovely clam shell, and go to pick it up only to have it wander away from you? Well, you may have seen this Crabday's crab:

Shellback Crab

Hypoconcha arcuata, H. parasitica, and H. spinosissima

this H. arcuata is a sneaky little surprise!

Did anyone else know these existed!?!? I didn't until I stumbled across a picture of them on The O'Keefe Family Website (no, I don't know the family; they just have really awesome crab eye candy!). The crabs pictured there are from North Carolina but all three species listed above are found all along the Atlantic coast of the US. Don't worry, west coasters, there's also a California shellback crab H. californiensis!

another H. arcuata showing how cozy a bivalve can be

While these guys rely on other animals' shells for protection, they are very different from hermit crabs. Shellback crabs are true crabs (infraorder Brachyuran) while hermit crabs are not considered 'true' crabs (infraorder Anomura). Also, while hermit crabs will protect their soft abdomens with 360° of a snail shell, shellback crabs only protect the top half of their "membranous" (aka soft) bodies by using old bivalve shells like clams or scallops.

this little juvie H. spinosissima is so small
it only needs a shell fragment for protection

What's really neat about these guys is they have modified 4th and 5th walking legs (kind of like how swimming crabs have leg modifications) that enable the shellback crabs to hook and almost suction themselves into the shell halves!

little known fact:
shellback crabs are incredible at yoga

I strongly advise you all to stretch before trying to impersonate the shellback crab! Safety first, am I right?

Thesis defense date!

Hi all! My thesis defense date is set:

April 18, 2012 

10:00 am (Alaskan Time)

So you can brush up on my thesis (while I do the same), here's an overview of my project:

A brief introduction and why I'm working with male snow crab

Gonad work

Hormones:

• Why study 'em?
• How I measure ecdysteroids
• What's methyl farnesoate, and what's it got to do with mating?
• What I use to measure methyl farnesoate - the HPLC 

OK, that should pretty well bring you up to speed! Wish me luck!

thumbs up for an awesome defense!

A fluff piece

Warning: this post contains NO scientific content!

A while back my friends bought a condo and decided to adopt a sweet little kitty for the new place. Well, really she's more like a well-aged woman. I guess you could say, were she tracking down young tomcats, she'd be a cougar. (Because of the age and gender... and feline-ness. Sorry.)

"not funny!" - cougar kitten

Anyway, we wanted to get her a little welcoming present and figured, what better thing to get than a catnip-filled crustacean toy!

who doesn't love lobster?

I checked with my cats to see if they approved

the verdict: it's good to go!

meet Zoe!

I think she likes it!

Success! Have you gotten any crustacean-themed toys, whether for yourself, a friend, a pet, or a study animal? If not, I suggest you get on that.

My chat with the F/V Seabrooke fans!

I had the honor of being a guest chatter in the Seabrooke Chat Room last night. It's a forum for fans of the F/V Seabrooke and that little TV documentary show about crabbing. You may have heard of it: Discovery Channel's Deadliest Catch.

the F/V Seabrooke crew

It was so great to have the opportunity to talk about crabs (be still my little heart) and answer snow crab questions in real time!

just some of the gabbing

and you know my avatar was a Fox!

So you don't feel left out, here are some of the topics covered with some links to my answers:

1. How old can snow crabs get?

This was a tricky one since it is really hard to age crabs. But there are estimates that they can live between 4 to 8 years after their terminal molt (at most... barring any predation). We learned about the terminal molt here, and we saw a SUPER old (8 1/2 years old) female here.

the old lady herself

2. How do snow crabs reproduce and how many babies can they have?

Oh man, can I talk about opie reproduction! All day, any day! Snow crabs aren't broadcast spawners; they actually copulate so that the males can deposit spermatophores (packets of sperm) into the female's spermatheca (pockets for sperm, you could say). Learn more about their anatomy here. And watch some mating experiment videos here and here. It's estimated that from all that mating, females can produce and fertilize over 80,000 eggs per clutch!

a big male grasping his little lady before sealing the deal

3. Do different crabs get it on, aka hybridize?

You know it! Snow crabs Chionoecetes opilio and Tanner crabs Chionoecetes bairdi make hybrid babies, who can then produce offspring of their own! Read more about hybrids in these posts.

male bairdi + female opilio = Chionoecetes hybrid

I feel bad because after reading through the conversation there were a lot of questions I missed, like do whales/walruses eat crabs? I'm hoping to participate in the chat room again, and until then I'll try and answer some questions I missed in future posts. 

Thanks to everyone who participated in the chat and thanks to Helen Green Ruckman for allowing me to talk about snow crabs with you all!

A slow (and steady) Crabday

It's Crabday! Crabday! Gotta get down on Crabday!

(So terrible but still so wonderful!)

This week's Crabday crab was inspired by the sargassum crab due to its unusual choice of real estate: a sea turtle's behind. While researching googling "sea turtle with crabs" I came across the aptly named

Turtle Crab

Cryptolithodes sitchensis

I can't get over that adorably flat rostrum!

These amazing-looking crabs are also called umbrella crabs due to their wide, smooth carapaces. Their claws and walking legs are all hidden with only their eyes poking out.

wrong umbrella crab...

there you go: see how it has the ability to protect all of its legs?

tah-dah! all of it's happy little legs tucked away like a turtle!

Turtle crabs range from southern California all the way up to southeast Alaska (hence another name, the Sitka crab). They're an intertidal species so you can probably spot them while beachcombing rocky intertidal zones (though I haven't had the pleasure of seeing one myself).

(now you can visualize what it must feel like to come across a turtle crab!

Thanks, YouTube!)

Turtle crabs are, unshockingly, quite slow (hey-oh), feeding on coralline algae (which doesn't move at all...) but their predators include otters, octopus, and sea birds. They are also constantly annoyed by sea hares (also seen here) egging them on for races. That... that last part's not true.

"Besides, I could totally beat any sea hare,

any day!" - turtle crab

You go, turtle crab. You go!

Team Pinchy

This past weekend I was outside enjoying the sun, just minding my own business, when all of a sudden I saw this:

What the? Are those? Yes!

Yes, they are people dressed up as crustaceans!

(Obviously, they were the only thing standing out in this picture.)

I just happened to be at the High Gravity Games, an outdoor extravaganza hosted by Alaskan Brewing Company at the Eaglecrest Ski Area benefiting the Red Cross. This crusty crew was honoring Pinchy, that famous lobster of Simpson's lore:

 Homer with his beloved Pinchy

And boy did they commit! Check out the crustacean style in action:

flying lobster!

the last leg of the Start-Up Cup relay was a human dogsled team

smooth finish (like butter?)

Have you been inspired to dress up like a crustacean recently (like Jenni last Halloween)? If so, was it a team event or did you let your crab flag fly solo?

it's OK to love crustaceans! (no matter what Marge thinks)

I'm dissoluting! Dissoluting!

I wonder what the pH of the water in that bucket was...

Last Tuesday we learned about ocean acidification and what that phrase means. The uptake of atmospheric CO₂ is creating more hydrogen ions in the ocean which lowers the pH, therefore making the ocean more acidic. So what does all this crazy acidification mean for calcium carbonate-encrusted crustaceans? Perhaps something like this:

oh dear.

Well, maybe that's an overdramatization; crabs aren't melting in ocean water with lower pH. But they are developing differently. There are a few studies going on here in Alaska looking at larval development in different pH water treatments. One such study by NOAA out in Kodiak (pdf poster here) looked at survival, growth, and calcium uptake of larval blue king crabs in pH treatments of ambient (normal levels in Auke Bay here in Juneau was 7.94 in 2010), minus 0.3 below ambient pH, and minus 0.5 below ambient pH. Sure enough, growth decreased in the lower pH treatments shown by an overall decrease in % dry mass.

"We're not growing! Oh, what a petri dish!"

Why is the development different if the acidified ocean water isn't actually melting the crabs' carapaces? Animals have the ability to regulate their internal acid-base relationship, and crabs do so by taking advantage of their calcium carbonate exoskeleton: when pH is lowered due to high levels of hydrogen ions, crabs can increase carbonate ions to bind with the hydrogen ions (thus making bicarbonate ions) through shell dissolution.

above is a crab with low pH due to all those pesky hydrogen ions

by using the calcium carbonate in its shell, it can get rid of 
some of those hydrogen ions by making bicarbonate ions

a dissolving shell results in less hydrogen ions and a higher pH (yay!)
plus an increase in calcium and bicarbonate ions

More research is in the works: UAF student Raphaelle Descoteaux is measuring any morphometric deformities in larval Tanner (Chionoecetes bairdi) and Dungeness (Metacarcinus magister) crabs that may occur in acidified seawater. We'll hear from her in a future Ask A Grad Student post, so stay tuned!

Read more crab OA research:

Pane, E. F., and J. P. Barry. 2007. Extracellular acid-base regulation during short-term hypercapnia is effective in a shallow-water crab, but ineffective in a deep-sea crab. Marine Ecology Progress Series 334: 1-9

Spicer, J. I., A. Raffo, and S. Widdicombe. 2007. Influence of CO₂-related seawater acidification on extracellular acid-base balance in the velvet swimming crab Necora puber. Marine Biology 151: 1117–1125

What's ocean acidification?

You may remember learning about acids and bases in high school. Every liquid is either acidic, basic, or neutral. You can measure this by measuring its pH: a neutral liquid has a pH of 7; anything over 7 (up to 14) is basic while anything under 7 (down to 0) is acidic.

oh, litmus tests! who didn't love these?

Say you have something with a pH of 8 but you want it to have a pH of 5. You can simply add an acid, or anything that's going to give up its hydrogen ions, because pH is just a measure of hydrogen ions in a solution. By adding acid, or acidifying the solution, you will lower the pH.

lots of hydrogen ions (in red) = acidic solution
lots of hydroxide ions (in blue) = basic solution

So, back to the main question: what's ocean acidification? It's when the ocean's pH gets lowered by the increase of hydrogen ions. The increase of hydrogen ions is from increased atmospheric CO₂. The ocean will absorb the CO₂, which will become aqueous and react with water (H₂O) to create carbonic acid. It doesn't stop there; carbonic acid can give up its hydrogen ions to become bicarbonate and then carbonate ions.

uptake of carbon dioxide into the ocean can
result in increased hydrogen ions (circled in red)

Where all this gets tricky is that organisms will use carbonate ions to make calcium carbonate (CaCO₃), but if there is extra hydrogen ions floating around, the carbonate ion will bond to them. Briefly, acidified ocean water becomes corrosive to calcified organisms.

spider crab larva: "Aren't I pretty?

All my little spines are made from calcium carbonate!"

How does this affect crabs? Stay tuned for research being performed in Alaska on larval crab development in acidified sea water (coming this Friday, March 9th)!

Why is this turtle so unhappy?

loggerhead sea turtle: "AHHHH!"

Could it be because:

(A) it is being accosted by a man in a speedo?

(B) it just realized it had been swimming east this whole time instead of west and was now off the coast of Spain, not Mexico? or

(C) it has an uncomfortable crab companion near its bum?

If you guessed (A) or (B), you obviously missed that this blog is about crabs. If you guessed (C), you're correct and have picked this Crabday's featured crab!

Sargassum Crab

Planes minutus

a sweet little sargassum crab

(not to be confused with the sargassum swimming crab, Portunis sayi)

"Hey! I'm swimmin' here!" - P. sayi

The sargassum crab, also known as the Columbus crab or gulfweed crab, is found on flotsam in the ocean. The most notable "flotsam" of all is the Sargasso Sea, and wouldn't you know it, the sargassum crab thrives there, floating among the Sargassum mats.

a minute P. minutus sayi mama! (found here)

(Thanks, Joe, for the species correction!)

When not living in masses of floating debris, P. minutus finds a home on loggerhead sea turtles, eating other epibionts like barnacles and parasitic amphipods! Unfortunately, the crabs seems to pick a not-so-cozy-for-the-turtles spot to call home:

peek a boo!

That's right, not one, but two sargassum crabs!
You can see the claw of the 2nd crab next to the 1st.

That's one tight squeeze! If I were these guys, I think I'd be looking out for the nearest Sargassum patch! (As for the sea turtle, I guess these crabs are found on a lot of them, so this turtle probably really was just upset about the speedo.)