Wednesday, July 28, 2010

Tips From a Crab-Samplin' Seafarer

  • Pack sweats. You can wear sweatpants all day, every day, and no one will judge you!
  • Seasick? Dramamine is good if you want to sleep through a tsunami (true story). Bonine (aka Meclizine) is where it's at: it's the less-drowsy form of Dramamine. I take one the day before I head out to sea to let my body adjust to it, then I take one my first and second day at sea. I also rely on ginger tablets or green ginger tea (yum!). **It's different for everyone though, so while this may work for me, something else might work for you**
  • Work on deck. For one thing, if you tend towards seasickness, fresh air is the best medicine (and puking on deck is way better than puking in the head). It's also a great way to burn calories: just staying balanced while standing can blaze through the cals! This is especially helpful if your cook specializes in tater tot casserole or there's an abundance of Cheetos (which, trust me friends, there always is) and you have a wedding dress to fit into a couple of weeks after you get back to land.
  • If you work with a head-set and you keep feeling like your hair is being constantly pulled by it, you're probably just being electrocuted over and over again... on your head... because it's wet everywhere, all the time. Genius.
  • What's left under your mattress by the person before you is fair game. Adam (my husband) once found a stack of "gentlemen's" magazines that was so high his mattress was noticeably uneven. I found something even better: 2 TOBLERONE BARS!!!! This prompted a Sundae Sunday party!

  • If you get a chance to walk on land, DO IT! I was once on a boat that only offloaded to trampers (and thus stayed on the boat for 27 straight days!), so I was never able to actually visit St. Paul until I worked on the NMFS trawl survey. It was beautiful and so worth just taking the time to meander!
touring St. Paul
northern fur seal

sneaky fox

Sunday, July 25, 2010

Hormones can be fun!

Part of this research project is measuring reproductive hormones in male snow crabs. But who really cares about mating hormones? The answer is YOU, especially when you were in high school.

in the year 2000

Crabs are just like people (OK, maybe not) in that they have glands that produce hormones, and these hormones then travel around their bodies affecting physiology and behavior.

Think of your pituitary gland and all the amazing things it's done for you (and for that guy from The Relic). Crabs have something similar: the X-organ sinus gland (XO-SG; see fancy drawing). Just as the pituitary gland controls the function of other endocrine glands, the XO-SG controls (by inhibiting) the function of the mandibular organs (MO) and Y-organs in crabs. And just as the pituitary gland produces follicle-stimulating hormone (FSH) to stimulate the ovaries and testes of humans, the MO produces methyl farnesoate (MF) to stimulate gonad development in crabs!

See, we're so similar!!

Thursday, July 22, 2010

The Tale of Legoless

Legoless was a recently-molted crab wandering the benthos of the eastern Bering Sea, when all of a sudden he was snatched up by a trawler! But this wasn't any trawler, it was the Aldebaran, searching the sea floor for groundfish and crabs during the NMFS trawl survey. And on the Aldebaran was a grad student, hoping to find a new-shell male snow crab to complete her project.

Flash forward to a marine research wet lab, where Legoless is in a saltwater tank with his fellow male snow crabs. They've been promised an opportunity to mate with some females in the spring, but these guys are getting anxious, and maybe a little bored with the herring, mussels, and salmon the grad student keeps feeding them. Legoless, being the sweet crab that he is, tries to calm everyone with a stirring rendition of Don't Worry Be Happy; crab pandemonium ensues.

Somehow, Legoless was able to escape alive (the grad student hoisted him from the tank and put him in his own special area), but he had lost so much: the others had eaten 6 of his 8 walking legs. Thank goodness he still had both of his claws for eating and flashing crab-signs.

Legoless in his sanctuary

You may be asking, crabs can regenerate their legs, so won't Legoless be fine? Can't he become Legolots? Unfortunately, friends, as a snow crab Legoless will terminally molt. Crabs and lobsters regenerate their legs with each successive molt as they grow, but because Legoless may only molt once more, he won't ever fully regenerate his missing legs.

And so Legoless sits, occasionally scooting over to a neighboring urchin, whistling as he goes.

Wednesday, July 21, 2010

Size Matters

One way to group male snow crabs is to use their relative claw size. Male opies can be small-clawed adolescents or large-clawed adults. Their claw size distinction is based on the height of their claw, or chela, compared to the carapace width.

It seems pretty straight forward, but the difference in claw size represents where each male snow crab is in his life cycle. Crustaceans molt/shed their hard exoskeleton in order to grow. Once they shimmy out of their old exoskeleton, they're really soft and vulnerable. But because they're soft, they're able to swell their bodies by taking in lots of water so that once their new shell hardens they're larger.

Snow crabs have a final, or terminal, molt. This means that after the terminal molt, they will no longer grow. When the males terminally molt, their claws become disproportionately larger compared to their bodies' growth. Why the larger claws? It's thought that larger claws (and larger muscles within them) give terminally-molted males a physical advantage when competing for females.

Not all male snow crabs terminally molt at the same time; some may skip a molt for a year or "choose" to stay adolescent for one more molt (it's not really well understood). Because of this, adult males come in a wide range of carapace widths. In order to determine which males are adolescent versus adult, I have to use a logarithmic discriminate function, which I won't get into too much, but I think it sounds impressive. It goes something like this:

Monday, July 19, 2010

Gonadosomatic Index: a how-to

Why am I measuring gonads? I measure the whole weight of a male crab, then I measure his gonad weight to calculate gonadosomatic index (GSI). GSI can be used as a proxy for reproductive fitness: the greater the index, the more that male has to offer any female with whom he mates.

Step 1. Determine shell condition:

Shell condition is a rough estimate of timing post-molt for a crab which I am using for comparisons:
Shell 2 is really fresh and clean, bright, with no barnacles or other epibionts
Shell 3 is a little darker, some scratches visible on the carapace, with few epibionts like small barnacles or leech egg cases
Shell 4 is dark, lots of abrasions on the carapace and legs, larger barnacles (given that they’ve had a longer time to grow), but not at the “very-old-shell” phase of beginning to deteriorate and become malleable
shell conditions: click for a larger view

Step 2. Wet weight:

Step 3. Estimating missing leg weight:

Some crabs may not have had all their legs (crab fights, trawl injuries, etc.) so I needed to estimate their missing weight in order to have the complete whole crab wet weight. This guy was missing three legs on his right and half a leg on his left (written as MR2, MR4, MR5, and DL2). Using his remaining legs, I can measure approximately what he was missing and add it to his wet weight.

MR2, MR4, MR5, DL2

Step 4. Morphometrics:

Measure the carapace width and chela, or claw, height. These measurements will be used later to determine claw size.

Step 5. Gonad removal:

It’s time to open the crab and weigh those gonads!

Step 6. Do the math:

GSI = gonad weight / whole crab wet weight * 100%

And there you have it: an easy 6-step process to measuring gonadosomatic index!

I measure crab gonads.

Yep, that's right: crab gonads. It's part of a study on male snow crab (Chionoecetes opilio) reproduction looking at hormones, structures (the gonads), and behavior. I am comparing these reproductive indices between the visually-appealing males that have recently molted ("new-shell") versus the males that haven't molted in at least a year ("old-shell").

Snow crabs are a commercially valuable fishery in Alaska. You may know them as the all-you-can-eat crab legs at Red Lobster or the "opies" caught on Deadliest Catch. Just like those fishermen, I went to the Bering Sea to bring some opies home to Juneau, AK for my project. Every summer the National Marine Fisheries Service does a trawl survey, counting, measuring, and sexing groundfish and crabs in an effort to estimate population abundance. Last summer I got to tag along and help sort and count the crabs.

a sampling of brittle stars and baby crabs

My guys were held in the live tank, brought back to Dutch Harbor, then flown to Juneau! It was quite a trip, and because of some unforeseen plane issues in Dutch (and one of my coolers of crabs being LEFT THERE!), a lot of my guys didn't make it. But their deaths were not in vain, for I was still able to measure their gonads! Hooray!!

removing the gonads