Monday, July 19, 2010

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


  1. Dear Marilyn,
    I loved your blog!
    I am starting a project at a university in Brazil with crabs too!
    But I need help with any questions!
    I wonder how open the crabs and identify the tissues!
    my crabs are from polluted mangroves of southeastern Brazil!
    I want to open them and perform analysis of pollutants in the shell, in the muscle and hepatopancreas!
    could you help me with tips on how to identify the organs and organisms as open easily?
    thank you!
    Alice Santos

  2. Hi Alice!
    Thank you so much for the compliment! You're project sounds very interesting!
    I always opened my crabs by holding their legs down with one hand and QUICKLY removing the top of their carapace wqith the other hand. This way it was swift (instead of putting them on ice for a time, which I think just prolongs their time out of water unnecessarily) and kept the organs together for easier identification and removal. In snow crabs the heart was always right on top, so I could remove it quickly to kill the crab - you can see a picture with the heart pointed out here:
    The hepatopancreas is also labelled in that picture. I'm not sure if your study animals will be too different from snow crabs, but as far as tissue identification goes, I would use muscles from the legs and find the hepatopancreas in the main body cavity of the crab under the heart. In the above picture, the hepatopancreas is the tan stuff (as opposed to the white gonads for males and orange gonads for females).
    I hope this helps! Good luck with your project and feel free to ask me any other questions!

  3. Thank you!
    I am very grateful!
    I will contact again if necessary!