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!

I wonder if they get hot flashes too

A recent paper has shown that female snow crabs experience menopause. OK, you’re right, they’re not calling it that, but the title says it all: "Histological studies on the spent ovaries of aged snow crabs Chionoecetes opilio caught in the Sea of Japan"!

Kon et al. (2010) sampled very old-shell female opies for GSI, ovarian color, and embryonic development. The purpose of this project was to estimate the fecundity of a population in the western Sea of Japan that has experienced a perceived increase in female average age due to artificial reefs and reserves.

Sea of Japan and Fukui Prefecture (starred) where the crabs were offloaded

With females getting older, the researchers wanted to determine if they were reproductively contributing as much as their younger sisters. Long story short: they were not.

The very old-shell females’ ovaries had dozens of nodules, which were darker tinted areas, indicating degeneration of unspawned eggs. Most of the ovarian eggs were strongly deteriorated, either through oosorption or oolysis, and none had the potential for ovulation.

red and black discolorations = nodules

The neat thing that this project discovered was how old one of their very old-shell girls was: one female was found with an 8 year 1 month old tag. She had been tagged directly after her terminal molt, which occurs at least at age 1½, so this female was more than 9½ years old!

Grandma opilio!

Previous estimates in the Sea of Japan had been 8½ years old based on tagging studies, while Bering Sea females may get up to 8½ years also (6 to 7 years after their terminal molt). Atlantic female snow crabs survive 4 to 5 years after their terminal molt.

This gal was OLD! I’m glad I aged a little better, at least when I was 9½.

Nerding it up, even in 1993

(photo courtesy of my dad, Jay Fox)

Read more and check out the histology slides:
Kon, T., M. Ono, and Y. Honma. 2010. Histological studies on the spent ovaries of aged snow crabs Chionoecetes opilio caught in the Sea of Japan. Fish Sci 76: 227–233.

Crabs are taking over AFS

It's that time of year again: the American Fisheries Society Alaska Chapter meeting! This year it's being held in our very own Juneau (yay! No flights for me!!). What's that you say, will there be any crab talks? Yes, oh yes.

Highlights of the meeting:

Crustaceans Are Cooler: Fisheries and Biology

of Crabs and Shrimps in Alaska

Chair: Ginny Eckert, UAF School of Fisheries and Ocean Sciences

Wednesday 9:45 – 11:25 am and 1:00 - 2:40 pm

Defining Genetic Population Structure of Snow Crab (Chionoecetes opilio) in the Bering, Chukchi and Beaufort Seas - Greg Albrecht

Variability in Reproductive Potential of Eastern Bering Sea Snow Crab, Chionoecetes opilio, in Relation to Spawning Stock Demography -  Joel Webb

Reproductive Indices of Male Snow Crab Chionoecetes opilio from the Eastern Bering Sea - Marilyn Zaleski (me)

Alaskan Crab Fisheries: An Historical Perspective - Courtney Lyons

Factors Influencing Snow Crab Recruitment: A Comparison Across Ecosystems - Laurinda Marcello

Red King Crab Paralithodes camtschaticus Larval Supply, Settlement Timing, and Benthic Habitat Structure - Jodi Pirtle

Growth Physiology of Juvenile Red King Crab Paralithodes camtschaticus Reared Under Laboratory Conditions - Miranda Westphal

Recruitment Mechanisms of Eastern Bering Sea Tanner Crab, Chionoecetes bairdi - Jon Richar

Crabs Are Not so Cool When it Comes to Management - Shareef Siddeek *

Should Some Minimum Size Limits be Amended? – Pribilof Islands Tanner Crab - Bill Bechtol *

* heavy hitters! (all the rest are student presenters)

Evolutionary/ Genetics Perspectives on Alaska Fisheries

Chair: Megan McPhee, UAF School of Fisheries and Ocean Sciences

Thursday 8:40 – 9:00 am

Alaskan red king crab (Paralithodes camtschaticus) population genetic structure - Scott Vulstek

Dynamics of Marine Ecosystems

Chair: Gordon Kruse, UAF School of Fisheries and Ocean Sciences

Thursday 10:35 - 10:55 am

Recolonization, Prey Selection and Resource Competition by Sea Otters, Enhydra lutris, in Southern Southeast Alaska - Zac Hoyt (This one doesn't sound crabby, but Zac is looking at sea otter predation on commercially valuable inverts including Dungeness crabs and Tanner crabs.)

Poster Session

Thursday from 11:55 am – 1:45 pm

Populations of ocean shrimp Pandalus jordani in the Gulf of Alaska - Aaren Ellsworth

The decorator dilemma: How Oregonia gracilis chooses what to wear - Greg Albrecht (student); Brenda Konar

Effects of larval rearing temperature on large-scale production of red king crab (Paralithodes camtschaticus) - James Swingle; Benjamin Daly (student); Jeff Hetrick; Ginny Eckert

Blue Genes: Population structure and paternity in blue king crabs (Paralithodes platypus) - Jennifer Stoutamore (student)

Long-term intra-cohort distributional shifts in the eastern Bering Sea population of Tanner crab, Chionoecetes bairdi - Jon Richar (student); Gordon Kruse

Seasonal gonad development of Parastichopus californicus in Southeast Alaska--Jessica Davila (student) (I know this isn’t crabby, but it speaks to me.)

I hope to see you there!

Thawing Crabs and Soufflé:

They wait for no one.

But while the soufflé may fall,

The crabs melt away!

a warning message for those who enter my lab

a package of crabs thawing for gonad sampling - love the pink tape, Joel!

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!