Found you!

If you follow Snow Crab Love on facebook, you may remember that I started keeping track of the non-crab related keyword searches that bring people to my blog:

this was just the beginning - it's gotten even weirder, I promise!

I'll share the final results at the end of the year, but in the mean time I was curious what other websites thought of Snow Crab Love and the search phrases that draws its way. I saw The Bloggess check her stats using Alexa, so I figured I'd check it out too. Here are the results:

TOP QUERIES DRIVING TRAFFIC TO SCL FROM SEARCH ENGINES

Totally weird, right? But when I google "the bullet crab", sure enough a link to this post comes up (currently it is the 7th link in the list).

a mantis shrimp's fist accelerates faster than a speeding bullet

(If you watch Arrested Development, you might get this photo reference)

The one that really confused me was "hat is fecundity". After pondering what it could mean and picturing things like this:

the hat had babies

I realized it was probably a commonly misspelled question of, "What is fecundity?" And what is it? Fecundity refers to how many babies something can produce (what their reproductive capacity is). For example, a female snow crab's fecundity can be measured in how many eggs she holds in her clutch (if you click on the link, check out slides 14 - 16). Or the fecundity of my hat (inspired by Princess Beatrice at the wedding of Prince William and Kate Middleton, and worn during a midnight 5K race) could be measured by how many little hats spring forth from it's bow-y goodness.

(this was a few years ago, but a good hat [joke] never goes out of fashion)

So now you know. I wonder if this is going to change my search analytics...

Trading WHAT for protection?

Oh, fiddler crabs, you're at it again.

"Who, me?"

You may already know that I have a deep-seeded distrust of fiddler crabs (despite this story I made up about one), but this next bit of science takes the cake. Few animals in the animal kingdom are monogamous. Hey, they all can't be like the mantis shrimp, right? But female fiddler crabs take this idea of polygamy to a whole new level! Female Uca mjoebergi will mate outside of their burrows on the sand flat for all the world to see. This rather public display with a male fiddler crab will secure that male's devotion in protecting her burrow. She trades sex for protection!

However, this broad's not finished with getting her, er, crab on. She'll next mate with a male inside her burrow, which is protected by her first mate. So the first male gets to mate, but it's the last male that will likely fertilize the majority of her eggs!

"There's nothing going on behind MY back, right? Right?"

The Slatyer et al. (2012) paper observed that the neighboring males were significantly more inclined to help after mating, so really the males are just as sleazy as the females.

cute, but still sleazy

Thanks to Meghan Garrison for telling me about this incredible crab behavior!

Read more:
Slatyer, R.A., M. D. Jennions, and P. R. Y. Blackwell. 2012. Polyandry occurs because females initially trade sex for protection. Animal Behviour 83: 1203-1206.

"Robocrab" or "You still can't trust a fiddler crab"

Researchers wanted to learn the factors affecting mate selection in fiddler crabs, specifically the Australian Uca mjoebergi fiddlers (thanks, Laurinda, for sending me this article!). You see, female fiddler crabs are VERY picky when it comes to choosing a male. Also, it's just plain fun to watch fiddler crab behavior! 

So the researchers mimicked the crabs in two ways:

1. make a robocrab arm to wave to the ladies at different sizes and speeds

2. lie to the ladies, as male fiddler crabs are apt to do, by making them think they are legitimate mates and not just some flailing piece of machinery (read another example of fiddler crab dishonesty here).

Are you a man or a machine?

Actually, you look like a pretty cute male U. mjoebergi!

It's actually pretty cool. Not surprisingly, females preferred "males" with larger claws, but they also liked faster waving speeds. Researchers were then able to learn that males purposefully situate themselves around smaller, slower neighbors in order to make themselves look better! They even go so far as to protect their weaker neighbors, but with an ulterior motive, not "Oh, I'm just a nice guy".

what, you think Ryan Gosling is the only one to say "Hey girl"?

Another study showed males "eavesdropping" on their neighbors to learn where the ladies are! Fiddler crabs. Pfft.

(Watch the robocrab videos here.)

Crab nerds united!

It's here! The 25th Lowell Wakefield Fisheries Symposium publication is out! The book detailing a meeting of so many crab nerds under one roof! And for 4 days, no less! Many participants have already gotten theirs, including my lab mate Miranda, but I'm still waiting on mine. That doesn't mean that I haven't hijacked her copy of Biology and Management of Exploited Crab Populations under Climate Change to get my crab-learnin' on!

I've referenced the knowledge I gained/people I met from the symposium here, here, and here, for a start. Today I'd like to highlight a paper from the book itself:

Preliminary analysis of spermathecal load of primiparous snow crab (Chionoecetes opilio) from the eastern Bering Sea, 2005-2008
Laura M. Slater, Kirsten A. MacTavish, and Douglas Pengilly

(What can I say? They had me at 'spermathecal load'.)

Their project was a monitoring program measuring spermathecal loads in primiparous female snow crabs from the eastern Bering Sea. They wanted to monitor the loads because a 2005 paper showed this group of females had low sperm reserves, which can mean that they won't have enough sperm stores to fertilize subsequent clutches after their first batch. (And remember, mating can be a dicey thing for female snow crabs!) The goal of the program was to see if large-scale interannual variability exists for female snow crab sperm reserves in the Bering Sea.

So what did they find out? First, clutches were mostly either 3/4 full or full, with healthy, viable eggs. Spermathecal loads in primiparous females had quite the range: from 0.001 g to 0.180 g! These loads are actually pretty low compared to crab stocks on the east coast, but since so many clutches were full of viable eggs it might not be an issue for these ladies.

The eastern Bering Sea was divided into three regions: northwest NW (area closest to Russia), central C (including St. Paul), and southeast SE (an area including St. George and Nunivak Island). Females were smallest in carapace width and had the lowest spermathecal loads in the NW region. There were also variations in loads over the different years of the study (as seen in the graph below), but only region and carapace width had any significant effects on the log-transformed spermathecal loads (ANCOVA, p < 0.05).

average spermathecal loads from the three regions of

the eastern Bering Sea during 2005, 2007, and 2008 

What does this mean? Sperm reserves in primiparous females are size-dependent (on the female's carapace width) and show spatial variation (between the different regions of the eastern Bering Sea). Using these differences, sperm reserves may end up being a helpful tool for predicting the presence and fitness of reproductively active males, which, as you know, is my #1 interest!

Crab Lab Fecundity

Is it just me, or is every other crab student at UAF having a baby? This lab is super fecund! (Take note, all you prospective students!)

For the most recent addition to our crab-lovin' group, Katie Palof (Pacific ocean perch geneticist) knit this amazingly cute little crustacean:

on route to the baby shower, enjoying the view of Douglas Island across the channel

livin' it up at the party!

It's not as cute as crab labber Joel and Karin's new baby boy, but it's a close second! It inspired me to search etsy (once again) for cute crab/baby stuff. Please, enjoy:

This lobster is both cute and educational:

remember how important cannibalism is for crustaceans?

(from this Chi-town shop!)

The simplicity of Lobber the crab-monster reminds

me of my little snow crab cartoons.

In short, I love him (from here)!

This sweet hat would help any little one match

their new crab toys pretty darn closely! Plus the

seller is from Kodiak, Alaska!! Represent!

That last hat made me think of this cute little number

my sister whipped up over at Happy Walrus,

inspired by this very blog! (How adorable is my neice!?!)

It's never too early to start teaching the little ones about crab love, and they can be ever the more cute while they learn!

Baby boom

I can track the search words people use when coming to Snow Crab Love and saw the question:

How many babies can a snow crab mother have?

Ahahaha! I love this kid's expression!

(picture from here)

I feel bad that the reader didn't get the answer they were looking for, so here goes:

Conan et al. (1989) estimated that snow crab females can produce between 31,000 and 90,500 orange eggs in one clutch. The top number drops slightly, to 88,800, when considering brown eggs (embryos that are further along in development) due to egg loss. (Read about the different colors of development here.)

eyed snow crab emryos attached to their mom

Similarly, Comeau et al. (1999) estimated 88,500 brown eggs within a large (85 mm carapace width) female's clutch, and for smaller females (55 mm carapace width) they estimated 31,500 eggs. Their study showed that fecundity for female snow crabs is positively correlated with carapace width (or size), which isn't too shocking. The egg estimations were based off of subsamples of clutches that were back-calculated to get the full clutch number (using a ratio of dry weight of 250 sampled eggs to the dry weight of the full clutch). Their study differed in that they thought large females may start out with as many as 116,000 orange eggs! This difference suggests greater egg loss during development.

full uneyed snow crab clutch = THOUSANDS of potential baby crabs

Females may lose eggs within their clutch due to some eggs remaining unfertilized, developmental problems, predation, or parasitism. Loss due to unfertilized eggs is why I'm concerned with male snow crab gonads: we want to make sure each male is giving the females he mates with enough sperm to fertilize at least one whole clutch.

These estimates don't include loss after hatching due to predation, cannibalism, and other problems (which accounts for a huge proportion of snow crab mortality), but this should give you an idea of how many babies a female can produce.

Fecundity Findings:
Comeau, M., M. Starr, G. Y. Conan, G. Robichaud, and J.-C. Therriault. Fecundity and duration of egg incubation for multiparous female snow crabs (Chionoecetes opilio) in the fjord of Bonne Bay, Newfoundland. Canadian Journal of Fisheries and Aquatic Sciences 56: 1088 - 1095.

Conan, G. Y., M. Moriyasu, D. R. Maynard, and Y. Chiasson. 1989. Factors influencing egg production in decapod Crustacea with two case studies: Chionoecetes opilio and Homarus americanus in the Gulf of St. Lawrence. ICES CM 1989/Mini 04.

Happy Easter!

I hope everyone had a wonderful Easter Sunday! I know for many people, an egg hunt was included in the festivities; there’s an egg hunt going on as I type this here at the UAF Juneau building. What colors did you find?

Just the beginning of my pile o' eggs!

So far, I’ve found some orange and purple eggs (and a white one), which makes me think of crab eggs!

the many colors of snow crab eggs/embryos

Moriyasu and Lanteigne (1998) color-coded the stages of development in snow crab embryos, so that when you catch females, you can determine how far along they are in their clutch maturation:

Moriyasu and Lanteigne's color scheme

Biological Field Techniques for Chionoecetes Crabs (Jadamec et al., 1999) and Biological Field Techniques for Lithodid Crabs (Donaldson and Byersdorfer, 2005) also describe the different categories for egg condition, which refers to embryo development. They include pictures of actual clutches that scientists can use to standardize different surveys’ data.

a myriad of egg colors:

the top clutches are Chionoecetes'

while the bottom are different king crabs' clutches

Based on these pictures, my eggs were a mix of uneyed snow crab Chionoecetes opilio embryos (orange) and uneyed king crab Paralithodes camtschaticus or P. platypus embryos (purple). The white egg could possibly be an eyed golden king crab Lithodes aequispinus embryo, or just a snow crab dud egg (unfertilized). Either way, it had two Butterfinger® chocolate eggs in there, so it was worth it!

Crab Egg Reading:
Donaldson, W., and S. Byersdorfer. 2005. Biological field techniques for Lithodid crabs. University of Alaska Sea Grant. AK-SG-05-03, Fairbanks.

Jadamec, L. S., W. E. Donaldson, and P. Cullenberg. 1999. Biological field techniques for Chionoecetes crabs. University of Alaska Sea Grant. AK-SG-99-02, Fairbanks.

Moriyasu, M., and C. Lanteigne. 1998. Embryo development and reproductive cycle in the snow crab, Chionoecetes opilio (Crustacea: Majidae), in the southern Gulf of St. Lawrence, Canada. Canadian Journal of Zoology 76: 2040 – 2048.

Snow crab moms get no respect

Do you ever just wish your kids would listen to you? “Don’t hit your sister.” “Practice for your piano recital.” “Don’t stick your finger there.” “Hatch right now!”

"I told you not to eat your sister!"

Well, you’re not alone. A new paper has come out in the Journal of Crustacean Biology (I may have squeeled when I saw this year’s purple cover) about Chionoecetes opilio larval release. Penny Kuhn, Sara Graham, and Jae Choi looked at whether or not hatch timing of embryos is dependent on their mothers’ presence. You see, some crab moms, like Sesarma cinereum and Uca pugilator, can control larval release. They may send signals to their embryos to start releasing enzymes important in the hatching process. Conversely, embryos of Dyspanopeus sayi and Rhithropanopeus harrisii may release their own pheromones to instigate hatching.

Kuhn et al. wanted to know which control was the case for snow crab larval release: mom versus embryo. They did this by detaching embryos from female snow crab clutches and placing them in completely dark tanks with ambient water (to mimic being hidden within the mothers’ abdominal flaps). Larval release was monitored for both attached and detached embryos and found to be “relatively synchronous”, meaning that the mothers don’t initiate hatching. In fact, detached embryos were able to successfully hatch up to 2 weeks after they were removed from the clutch!

hatching of attached and detached eggs from one of the study female opies:

see how the peaks are pretty consistant/synchronized?!?

Previously, hatching synchrony had been seen up to 10 days post-removal in Homarus gammarus and only up to 5 days post-removal in Rhithropanopeus harrisii, so the matched hatch-timing 14 days after separation from mom is pretty impressive. Clearly, snow crab babies were not relying on any message or signal the moms might have given.

So snow crab moms may have no say when their larvae are released into the ocean; they just get no respect!

Mom v Embryo:

Kuhn, P. S., S. Graham, and J. S. Choi. 2011. Influence of senescent algae, temperature, tides, currents, and embryo detachment on Chionoecetes opilio (snow crab) larval release. Journal of Crustacean Biology 31: 100-105.
(The bulk of the paper also looked at different potential triggers of larval release: senescent algae, tides, currents. I don’t want to give any more away though, so you’ll have to read it yourself! Also, you can find the references for the other cited research in the Kuhn et al. paper.)

CSI for crabs

Remember that sweet male snow crab who protected his female by hoisting her in the air? Well, I have hard evidence that they did in fact mate:

spermatheca from the lucky lady



Pretty awesome, huh? Joel Webb removed the spermathecae from my females after their mating experiments to see if copulation really occurred. The dark color is from the spermatheca's reaction to a foreign object (the spermatophores). Joel showed me how to dissect the spermatheca so that I could measure the sperm load too! You can see that the male didn't quite, er, fill her up:

So there you have it! The proof is in the spermathecae!

Let's hear it for the boys

Someone once asked me why I’m studying male snow crab reproduction. My first response was, “Why not?” But the real answer is Joel Webb is monopolizing all the female crabs! No, that’s not the real answer, but it’s true. He is.

me with one of Joel's females... sigh...

The real answer is snow crab is a male-only fishery with a minimum size limit (the females aren’t targeted and, if caught, get thrown back). Removing large males can negatively affect a population because it may be giving smaller males more opportunities to mate. The idea is, because snow crabs terminally molt at different sizes, the males who are smaller than the fishery size limit will never be harvested, and therefore will be around for more reproductive seasons than the larger commercially targeted guys. If maturing smaller is a genetic trait, the smaller males’ offspring may tend towards maturing smaller too. It’s the classic case of shrinkage…

Oh, wait, that’s not what that means? Oh, well…

ANYWAY, it’s necessary to understand the role males play in reproduction, not just the females, when trying to estimate population size for management. The eastern Bering Sea stock was declared overfished by NMFS in 1999, and while the fishery continues, the stock is still in a rebuilding phase.

snow crab estimated biomass and landings showing the decline in 1999

That’s right guys, you’re important too.

Chivalry's not dead

While I’m glad I’m not a female snow crab, male snow crabs can defend females for mating, not just for munching.

This guy was in it to win it, even going so far as lifting the female out of the water to keep her from the other male! What a fighter!

Boys have HOW MANY and girls have WHAT?

I know we all learned a lot from Kindergarten Cop, but some things even Arnold can't teach us!

This blog is about love for snow crabs, but also about snow crab lovin', and as such I feel the need... the need for speed. NO! Sorry, I just kinda slipped into that. No, I feel the need to explain snow crab sexual structures.

First the females: their abdominal flap is wide, almost the entire width of their body when they're mature. This allows them to hold as many fertilized eggs between their abdominal flap and body as possible. Next they have two spermathecae under their abdominal flap, where males deposit spermatophores (capsules of sperm) for the females to use at their leisure when fertilizing eggs. It's said the sperm in the spermathecae are viable for up to 3 years! Storing sperm is a handy way to fertilize subsequent clutches without having to find a male and mate again, especially since mating can be so violent.

juvenile female abdominal flap

male abdomen

Why do females have two spermathecae? Because males have two gonopods (crab penises)!! Yep, it's not just for sharks; snow crab males are cool too. The gonopods are hidden under their abdominal flaps, which are quite skinnier that females' flaps.

two gonopods under the male's adbominal flap

Males will hold the females in an abdomen-to-abdomen position in order to do the deed, then guard the females afterward in case there are any other males around. Once the females extrude their eggs and fertilize them, the males know their job is done, and they go their separate ways.

Why I'm glad I'm not a female snow crab

Understanding any hormonal differences between new- and old-shell males is one thing, but getting to see a new-shell male compete with an old-shell male for a female is the icing on this project's cake! Imagine my excitement when my first female molted (and wasn't eaten by her girlfriends) and was ready to mate - females mate after they've molted to maturity and are still soft. It was 6 pm and the experiment needed to be filmed for 12 hours, so instead of just waiting to start the next morning, I did what any normal person would do: asked my husband to get the sleeping bags and some Chinese take-out, and got started!

Adam at the lab

I put my new, precious, soft-shell female into the tank with two males and some herring (you know, in case they wanted a snack...) and started taping. Things were really slow for the first 6 hours, then things got crazy!

The small crab is the female, playing the edible rope in a medieval tug-of-war: the old-shell male (with white barnacles attached to his back) ate 2 1/2 of her legs! Don't worry, I took her out and put her in her own little hospice area. And then I sampled the males for their gonads.

But how representative is this behavior compared to opies in the wild? Maybe more representative than you'd think. This carnage was captured in the Bering Sea by ADF&G:

And that's why I'm glad I'm human.