Misleading Mammal

Well, they fooled me. There’s a seal named Lobodon carcinophaga, which means “lobe-toothed crab eater”: the crabeater seal.

possible culprit of crab predation, or is it???

But you know what, these seals DON’T eat crabs. Crabs aren’t even on their radar (these seals live in Antarctica, where crabs do not roam). They eat krill with their specialized teeth.

crabeater seal skull on display at the Crary Labs Museum in Antarctica

tastey krill

And their teeth must be pretty special, because they eat 80 million tons of krill a year! Then leopard seals eat them.

AHHHHHHHH!

So now I know, and knowing is half the battle.

Note: there aren't polar bears in Antarctica either. Just so you know.

Merry Christmas!

How fitting is it that the most wonderful time of the year has its own island (Christmas Island) and that island is also called “the kingdom of the crabs” and “the crabbiest place in the world”? Two happier things couldn’t be combined!

Coconut crab (Birgus latro)

(photos from ag.gov.au)

Christmas Island red crabs (Gecarcoidea natalis)

heading to sea

Christmas Island is home to 20 terrestrial and intertidal crabs, including coconut crabs (a personal favorite: I’ve seen these guys in the Solomon Islands) and red crabs. The latter are famous for their massive march to the sea from their jungle home:

(I strongly encourage you to watch all the National Geographic videos on the red crab migration [millions of crab babies!!], but I’ll warn you now: you will come to hate yellow crazy ants!)

SO MANY BABIES!

Red crabs undergo an incredible physiological change when embarking on their journey: they have to get their muscles from couch-potato to marathon-runner, which involves changes in their gene expression (rather than an 18 week training program. Lucky!). Scientists from the University of Bristol just published an article on red crab leg muscles, and it is covered quite splendidly here.

I’ll leave you with my take on a Christmas Island Christmas tree:

HAPPY HOLIDAYS!

Red crab reading:

Postel, U., F. Thompson, G. Barker, M. Viney, and S. Morris. 2010. Migration-related changes in gene expression in leg muscle of the Christmas Island red crab Gecarcoidea natalis: seasonal preparation for long-distance walking. Journal of Experimental Biology 213: 1740-1750.

Interagency Crab Meeting 2010

Another year, another fun get-together of all the Alaskan crab researchers! There's nothing like hanging out with a room full of crab lovers (I was trying to write that phrase in latin, but it would come out as cancerphiles or something, and that just didn't express the right message).

This year the meeting highlighted Crustacean Enhancement and Genetics,

with these presentations:

Developing genetic fingerprinting techniques for lobster seeding trials in New England - Rick Wahle (University of Maine) [I love lobsters and got to work with them on Long Island!]

Some population genetic considerations for red king crab management in Alaska - Dave Tallmon

Update on genetic studies of snow and king crabs at ADF&G - Stew Grant

three crab girls enjoying the sights:

Courtney Lyons, Miranda Westphal, and me

Student presentations included:

Evidence of predator-induced behavioral plasticity of juvenile red king crab (Paralithodes camtschaticus) - Ben Daly

Qualitative modeling of the Pribilof Island blue king crab fishery - Courtney Lyons

Growth of juvenile red king crab, Paralithodes camtschaticus, in Alaska - Miranda Westphal

Interannual variability in pre-hatch fecundity of eastern Bering Sea snow crab, Chionoecetes opilio - Matt Catterson

Defining population structure of snow crab (Chionoecetes opilio) - Greg Albrecht

Gonadosomatic index in male snow crab, Chionoecetes opilio, from the eastern Bering Sea: another look - Molly Zaleski (me)

Variability in reproductive potential of eastern Bering Sea snow crab with environment and stock demography - Joel Webb (the host with the most)

# Effects of ocean acidification on larval development in Alaska Tanner crabs (Chionoecetes bairdi) – Raphaelle Descoteaux

# Ecosystem-based fisheries management and population dynamics of the collapsed, Yakutat Bay Dungeness crab (Cancer magister) stocks in Southeast Alaska: A proposal – Jared Weems

# poster presentation

Ask A Grad Student: Greg Albrecht

Don't let the fish throw you off; Greg is a true crab lover all the way! While not studying snow crab genetics, he's playing dress-up with decorator crabs. He's a model for the rest of us!

Age: 27

Degree: MS Marine Biology

Current City: Fairbanks

1. Describe your project, in 4 sentences or less.

My project focuses on defining the genetic population structure of snow crab within the Bering, Chukchi and Beaufort Seas. I'm using 7 microsatellite markers and have 613 samples collected from 13 locations. The hypothesis I'm testing is that due to their long distance larval dispersal abilities the entire stock will have low genetic differentiation. This is an important question for management of the current fishery and figuring out what's going on in the arctic.

a lovely C. opilio

2. Have you come across any opilio-bairdi hybrids, and if so, have you included them in your genetic analysis? In your opinion, are they truly 2 separate species (C. opilio and C. bairdi) , or simply subspecies of one another? Let’s fuel the debate!

To my knowledge, none of the crabs sampled were hybrids; however, that's hard to tell since identifying them can be difficult especially if they aren't first generation. Genetic techniques can be used to distinguish the two, or at least what portion of each species they are; however, we didn't conduct any of those tests or collect any Tanners, which would have been necessary.

So yeah... a species: they are typically defined by two animals that can interbreed and produce fertile offspring; however, that means that opies and bairdis would be the same. There are other examples of this like the cutthroat and rainbow trout that make a cutbow hybrid. So, to the best of my knowledge (which is just basically Wikipedia and asking the grad student in the office next to me) often times genetics and the ecological niche that they fill are used to define the species. Opilio and Tanner crab have different habitat limitations (mostly based on temperature) and although they overlap, I don't think a Tanner would stand a chance in the Arctic. So with that and the significant differences we see in their DNA (at least at this point... given that hybrids don't rule the Oceans... yet) we can say they are still different species.

Now as to "subspecies" well that's kind of a fuzzy line in my opinion. I think that technically subspecies can interbreed, but don't very regularly due to behavioral differences and ecological barriers (i.e. dogs and wolves). In my opinion, Tanners are still morphologically differentiated in a number of ways (size being one big one) and at this point are still defined by different habitats (thermal tolerances).

3. You have also been studying decorator crabs and their decoration choices. What led you to this work and what’s the weirdest thing you’ve seen a decorator crab choose?

I have long thought decorator crabs to be cool, but diving in Kachemak Bay this past summer gave me an opportunity to start a small study on their behavior. I have found flagging tape, viable fish eggs and of course lots of algae on crabs; however, the funniest finding was a crab sampled from a location containing a mix of algae and trash (95% and 5% cover, respectively) who had placed a piece of an old windshield wiper on his carapace.

decorator crabs showing off their flair


4. You eventually want to teach high school: why? (What sparked this interest?)

So that I'll have summers off to play with decorator crabs and go fishing... oh yeah, and I guess to "inspire" the next generation.

 oh snap!

I'm inspired!

5. What is your favorite piece of crab paraphernalia?

My crab pot

crab on!

Thanks, Greg! And I have some great crab dip recipes, just in case you don't know what to do with all that king crab. Just saying. 

Glittered holiday crab cards

Taking a page from Martha Stewart, I decided to share a fun card idea with you:

Step 1:

Download this crab cutout and print it on white paper or cardstock (you can also make a template to trace onto your paper each time). Cut along the black lines, leaving the tips of the legs and the sides of the claws connected where the blue dashed line runs. (Don't cut the legs and chelae off though, and try not to eyestalk-ablate them.)

Step 2:

Fold your crab! If you used a template you don’t have to worry about lines showing, but if you just printed directly onto the cardstock, make sure the printed side is face down. Add glitter!! I used glitter paint, but Martha is a fan of the glue-glitter combo.

Step 3:

Glue your crab to a cardstock background (I used yellow, but you could use whichever color you prefer) and delight a loved one with your home-made card!

I linked up to this blog:

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.

Welcome Allacanthos yawi!

A new crab species has been discovered, and not from some deep-sea, hard-to-find chasm, but from a river in Costa Rica! Allacanthos yawi is a decapod crustacean in the family Pseudothelphusidae, and was discovered 1,000 meters above sea level in the Río Volcán drainage (Buenos Aires County, Puntarenas Province, Costa Rica)!

A. yawi showing off his lovely green carapace (scale bar = 10 mm)

The crab was found by Luis Rólier Lara while he was scouting for the Costa Rican Electricity Institute (they want to build a hydroelectric plant), identified by Ingo Wehrtmann from the Museum of Zoology and the School of Biology at the University of Costa Rica, and described by Célio Magalhães from the National Institute of Amazonian Research. Melania Pérez, a Costa Rican archeologist, gave the crab its species name yawi, which means “crab” in the indigenous language Cabécar (or more fully “river crab that lives under rocks”, as reported by Tico Times).

the pretty mottled female A. yawi (scale bar = 10 mm)

Let’s wish this newly-discovered crab luck! With battles against expanding pineapple farms, hydroelectric projects, and pollution, this endemic little species may need it!

Pineapple attack!!

(A. yawi is a preserved male from Magalhães et al., 2010)

Read about it:
Magalhães, C., L. R. Lara, I. S. Wehrtmann. 2010. A new species of freshwater crab of the genus Allacanthos Smalley, 1964 (Crustacea, Decapoda, Pseudothelphusidae) from southern Costa Rica, Central America. Zootaxa 2604: 52–60.