Double Ouch!

It's science fair season, and if you're lucky like me, you're up to your eyeballs in mentoring and facilitating fun experimental designs. This past weekend I was able to help my student run some behavioral experiments with hermit crabs (more on that later), and while we were removing the crabs from their shells (by gently holding the shell steady at the surface of a small tank: the hairy hermit crab, Pagarus hirsutiusculus, will wiggle its way out of the shell and drop to the bottom of the tank) we noticed this:

 

The hermit crab is about to enter its shell, but see that red blob?

Do you know what it is?

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(I'll give you a moment to think)

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It's a rhizocephalan! WOOO! And GROSS!!! This poor little hermit crab is being parasitized by a reproductive-organ-hijacking barnacle. Remember learning here that rhizocephalans will sterilize their host and use the host's energy to raise and protect their own little parasite larvae. I was used to seeing these parasites on king crabs, but it is pretty common for hermit crabs to have rhizocephalans on them, at least in Auke Bay, where our science fair animals had been collected. In fact, back in 1996, researchers went out and collected 169 hairy hermit crabs from Auke Bay and found the parasites on about 13% of them! But don't worry, because they also found this:

The blobs marked "A" and "B" are rhizocephalans (Peltogaster paguri),

but the "C" blob is a HYPERPARASITE on the "B" rhizocephalan! 

YEAH! Take that, parasite! You've got a parasite of your own! (Nature: it's an awesome, scary place.) The rhizocephalan's hyperparasite is Liriopsis pygmaea, an isopod that will sterilize its host. It's a nice case of karma, am I right?

Cod are just like people:

They love to eat snow crabs!

You may remember meeting Laurinda Marcello through an interview last year as a student, but she's since graduated and published her results! Her paper looked at how snow crab recruitment is affected by water temperature and cold area extent, spawning stock biomass (how many crabs are out there makin' babies), and the biomass of crab predators (cod!). As a bonus, she compared these relationships between the Bering Sea and the Canadian North Atlantic.

What did she find out? Let's start with the predators! We know that cod like to eat snow crabs. I've had a cod puke little baby snow crabs on me (it had been through a lot, the poor cod, so I wasn't mad or anything). And check out this piece of knowledge:

snow crabs (in the orange square) make up a relatively large percentage

of both frequency of occurence (%FO, on the top half of the figure)

and stomach content weight (%W, on the bottom half) compared to

red king crabs and Tanner crabs in Pacific cod stomachs (from this paper)

Interestingly enough, Laurinda's study only saw an inverse relationship between predator abundance and snow crab recruitment in one study area! The rest of the areas had no real pattern. This could suggest that, while cod eat snow crab, there may not be enough predation on their part to be considered a top-down effect on snow crab recruitment. (That's a big statement up in here!) However, she warned us not to be too hasty with this conclusion as predator biomass may not mean direct predation pressure on the crabs.

Moving on, spawning stock biomass in both the Bering Sea and one portion of the North Atlantic study area was inversely related to recruitment. What? More baby-makers mean less babies? Crazy town sea, right? Laurinda posited that since snow crab reproduction relies on not only males and females to be present, but for them to be within each other's vicinity, simply looking at the number of adults may not accurately represent the number of mating adults. There's also the case of cannibalism in snow crabs: more adults mean more cannibalistic mouths to feed!

"Get into my belly!" - large snow crab

The big result was that the main factor associated with snow crab recruitment was the ocean climate. From her paper, "[t]his strongly supports our hypothesis... that cold conditions during early life history stages promote subsequent snow crab recruitment."

the colder the temperature (to a point), the more recruits to the fishery!

Cool! (Get it? wink.) Congratulations on the paper, Laurinda!

Read the full paper:
Marcello, L. A., F. J. Mueter, E. G. Dawe, and M. Moriyasu. 2012. Effects of temperature and gadid predation on snow crab recruitment: comparisons between the Bering Sea and Atlantic Canada. Marine Ecology Progress Series 469: 249 - 261. doi: 10.3354/meps09766

OUCH!

OK, I think we all thought about this when dumping a lobster or crab into a boiling pot:

"Yikes! At least they can't feel this. Right? Right guys?"

WRONG!

A new study in the Journal of Experimental Biology that is making the rounds on the internet looked at shock avoidance by the shore crab Carcinus maenus. Crabs were placed in a tank with two shelters: one safe and one rigged to shock them. Over a few trials, the crabs avoided the shocking shelter and chose the safe one; by avoiding the shock after trial and error, the crabs were exhibiting a learned behavior from what we, as humans, would perceive as pain. In other words, the crabs learned the one shelter would hurt them while the other one would not, and after a few painful shocks, they would seek out the shelter that wasn't harmful.

a tale of Goldi-crab

This study's results are not so shocking (hey-oh) to me - my snow crabs would consistently massage their limbs after fighting with fellow crabs or reach for their missing limb at the joint when another crab would rip it off. That's why my heart really went out to my dear Legoless.

"I have two legs!" - Legoless in his sanctuary

It's also why I'm so passionate about how I went about sacrificing my snow crabs, and how we prepare Dungeness crabs when we eat them. In a word: QUICK! There's all this "humane" talk about chilling lobsters and crabs in the air for awhile to bring their body temperature down until they stop moving, but, in my mind, that's just slowly suffocating them as they can't breath as well out of water. Also, do you really think an animal who is used to seawater is going to appreciate being on a mass of melting fresh water? I mean, osmoregulation, people.

remember learning about osmoregulation in lyre crabs?

When I had to sacrifice my crabs to measure their gonads, I would take them out of the water, whisper an apology, then swiftly, in one motion, rip their carapaces off of their bodies and remove their heart. Boom. Done. No waiting around for the inevitable. There is this idea of stabbing the lobsters in the heart before boiling, and that may work, but again I'd advise against forcing them to sit on ice just so that you are not so afraid to handle them while they're still active. Man up, people!

Read more:

Magee, B., and R. W. Elwood. 2013. Shock avoidance by discrimination learning in the shore crab (Carcinus maenas) is consistent with a key criterion for pain. Journal of Experimental Biology 216: 353-358.

On your marks, get set, Tanner crab fish!

A Tanner crab (Chionoecetes bairdi) fishery is opening tomorrow off of Kodiak. Where, you might ask? Right here:

beautiful Kiliuda Bay

But wait, what's all that racket going on in Kiliuda Bay, home of the upcoming Tanner crab fishery?

Oh, this old thing?

That's right. Sitting in Kiliuda Bay is the Kulluk, Shell's oil rig that had run aground off Kodiak January 1st. The Kulluk is using Kiliuda Bay as safe harbor, but as such, any boats that will be participating in tomorrow's fishery will need to get special permission from the Coast Guard to do the same if the fishermen want to sleep in the bay. As for the fishery itself, the Kulluk should be out of the way as it is anchored in a nursery area for juvenile Tanner crabs and is therefore closed to the fishery.

Kiliuda Bay is enlarged showing the grey area closed to fishing

As long as the Kulluk stays "intact and upright" it shouldn't pose a threat to the crabs. And we can totally trust that nothing like that would happen, right? I mean, it was built in 1982 (and is older than me) but survived a season in the Arctic and didn't spill any oil during the grounding, so...

(waves crashing over the Kulluk when it was first grounded)

Sorry, all that craziness aside, the Tanner crab fishery is opening and you can place orders for pick up in Kodiak, Homer, or Anchorage! The Bering Sea Tanner fishery is closed for 2013 so this Kodiak fishery is a great opportunity for Alaskans (or at least those not privy to Southeast Tanners) to get some fresh C. bairdi meat and support local fishermen.

 a good Kodiak catch

Are you involved in the Tanner crab fishery or from Kodiak? Let me know how the fishery goes and what, if anything, you had to change to accommodate the Kulluk!

nerd

What did you do during your lunch break today? I found the one ring that rules us all, hid it the only place befitting such a ring, and wrote a clue for the owner of the ring in Elvish:

If you can't read Elvish (or my attempt at it), it says:

"The one ring is safe in the

clutches of an immortalized

denizen of the deep

~MZ"

Obviously, the only "denizen of the deep" deserving of such an honor is this bronze beauty (remember meeting him here?):

 "My precious!!!!"

(Props to Pat Barry for figuring out the message!)

Happy New Year!

How has everyone's first week in 2013 been? Did you bring in the New Year with a bang or with quiet reflection on the past year? I have a feeling I know what this guy did:

someone went a little overboard with the silly string

To be fair, the hermit crab here, Pagurus prideauxi, wasn't the party animal here. Those pink strings were secreted from the cloak anemone (Adamsia carciniopados). While they seem fun and festive, the strings are actually poisonous tentacles to protect both the hermit crab and its symbiotic friend!

the anemone protecting its hermit crab pal while he courts a little lady

(photo by Dive Tramp Darryl Mayer)

I always love seeing symbiotic relationships with hermit crabs and anemones. It seems like such a wonderful way for an anemone to get around! The cloak anemone really has it figured out though: while hermit crabs normally have to find larger shells to fit into, and thus have to ditch their old small shells despite any friends they might have picked up, the cloak anemone becomes a sort of protective shell itself for the hermit crab. It does this by creating a chitinous layer called a carcinoecium which helps extend the original shell's coverage!

a sad crabless anemone found on a Scottish beach - note the structure of

the carcinoecium that used to protect a hermit crab's face

Because the cloak anemone adds to the hermit crab's home, the hermit crab never has to worry about finding a bigger shell. That means these crab-anemone pairs are set for life! They're like the Pooh Bear and Piglet of the marine world!

"Silly ol' crab!" - cloak anemone