Friday, July 22, 2011

Crabday: Horseshoe Crabs

This Crabday is dedicated to:

Horseshoe Crabs!


Wait, say what now??

OK, so a horseshoe crab isn't really a crab, per say, but more closely related to spiders (phylum Arthropoda, but subphylum Chelicerata like spiders instead of Crustacea like snow crabs). The common name "horseshoe crab" covers four living species within the family Limulidae: the Atlantic horseshoe crab Limulus polyphemus, the mangrove horseshoe crab Carcinoscorpius rotundicauda, and the congeners Tachypleus gigas and T. tridentatus.

a simple family tree showing the relationship between
horseshoe crabs, spiders, and true crabs like our snow crab

Despite not being true crabs, when I was working in the crustacean department for the NY State Department of Environmental Conservation I monitored the horseshoe crab harvest along with the lobster population. Fishermen harvest both males and females, and target the females more so because the females are so much larger than the males. (I never feel good about that kind of arrangement, but perhaps that's just me.) Fishermen use horseshoe crabs as bait for whelks (most commonly the channeled whelk Busycotypus canaliculatus), which they can then sell as scungilli. (This also explains why, when I see large snails up in the Bering Sea, I identify them as whelks... and then get made fun of. But now you know!) They are also harvested in some areas for their blood, which is then used in medical research.

These animals are obviously a hot commodity, and as such suffer from potential overharvesting. This becomes an even bigger problem because horseshoe crab eggs are the primary meal for red knots, who make an annual stop in Delaware Bay, Maryland for this treat. This may not be a sad tale, however, because at least in 2009 the red knots appeared to be gaining enough weight during their stop in Delaware Bay to make the flight north to the Arctic.

a red knot amid horseshoe crab carnage

Anywho, I want to end this Crabday with a lesson on how to properly hold horseshoe crabs. Pick them up by their "heads" and not their "tails"! The "tail spine" is actually a telson which helps them turn over if they've flipped on their backs, so it is important to not damage it. It is NOT a stinger like a sting ray: it will not hurt you. So be nice and friendly and only handle them by the front of their carapaces.

this little guy is perfectly demonstrating
how NOT to hold a horseshoe crab


Tuesday, July 19, 2011

Arctic Opies

I’ve mentioned invasive crabs here (Chinese mitten crabs), here (kings in Antarctica) and briefly here (green shore crabs all over), but did you know snow crabs Chionoecetes opilio are turning up where they aren’t expected too?

Shocking, right? Because who wouldn’t want snow crabs around? Well, maybe the other critters in the Barents Sea, including the previously
introduced red king crab (Paralithodes camtschaticus). Snow crabs were first caught by Russian vessels in 1996 (5 in total) and have apparently grown in numbers since then.

"normal" distribution of snow crab Chionoecetes opilio in grey;
the blue star shows the Barents Sea

Alvsvåg et al (2009) showed, through surveys from 2004 – 2006, that opies have in fact established a population in the Barents Sea. Not only were there large males and females, but the researchers also measured little opies, indicating successful recruitment into the Barents Sea population.

quite the range: large and small male opies from the Barents Sea

In their snow crab chapter of the new book, In The Wrong Place, Agnalt et al (2011) also mentioned the abundance of juvenile snow crabs during yearly Barents Sea surveys; about 40% of the measured crabs were juvies! New recruits in the Barents Sea suggest that this snow crab population either has no competition with other benthic animals or they are out-competing their benthic neighbors for food/space. My question: what could this mean for the red kings?

Invasive opies:
Alvsvåg, J., A.-L. Agnalt, and K. E. Jørstad. 2009. Evidence for a permanent establishment of the snow crab (Chionoecetes opilio) in the Barents Sea. Biological Invasions 11: 587 – 595.

Friday, July 15, 2011

Crabday: Ghost Crabs

Happy Harry Potter Day! I can’t tell you how excited I am to see the LAST movie!!! I made my husband wait in line at midnight in Chicago when the last book came out, so I’m actually thinking of waiting for him to get back from Russia before I see the Deathly Hallows Part 2. Key word: thinking!

In honor of the culmination of the Harry Potter series, this Crabday we’ll learn about the 
Ghost Crab!

The common name ‘ghost crab’ refers to several species found all over the world! Many of you on the east coast of the US may be familiar with Ocypode quadrata, while those of you in the Indo-Pacific region may know Ocypode pallidula as your friendly ghost crab.

Ocypode quadrata hanging out at Myrtle Beach, South Carolina

Ocypode crabs get their ghostly name from their pale colors across their genus. Only the painted ghost crab O. gaudichaudii is bright orange (found in the Galapagos, and from El Salvador to Chile), but I guess there’s an “orange crab” in every family. (Eh, see what I did there? Let’s start using that phrase instead of “black sheep”. New crab movement!)

orange is the new white: a painted ghost crab in the Galapagos

The name may also refer to their ability to hide quickly (ie disappear), a skill referenced in the genus where Ocy means swift and podi means foot. When I was in Fiji we’d just get a glimpse of a little white crustacean before it sprinted to its home; the local dogs had a hard time trying to snatch the speedy crabs up, and no wonder when ghost crabs can run about 100 body lengths/second (compared to a cheetah’s 10 body lengths per second)!

this horn-eyed ghost crab O. ceratopthalma from New South Wales
must be taking a break from all the running

Enjoy the many varieties of ghost crabs, and enjoy the movies!

Tuesday, July 12, 2011

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!

Friday, July 8, 2011

It's Crabday!

It's Crabday, Crabday! Gotta get down on Crabday!
Fun! Fun! Fun! Fun!

OK, so this isn't as catchy as "Caturday" or "Sundog" over at, but I figured it would be a fun way to celebrate Fridays.

Which crab should I... talk about first?
(I kinda gave up on that last line.)

Coconut Crab!
Birgus latro

These crabs are so huge and so beautiful! Their coloration has this amazing shade of blue that I fell in love with at first sight in the Solomon Islands. (Oh yeah, I got to see these beautiful crabs in person during a tropical marine biology class in 2004!) I first mentioned them here.

look at that beautiful mug!

B. latro are named coconut crabs because their large chelae can open coconuts for them to eat. This ability to crunch through coconuts has led people to suggest the crabs' ability to attack human skulls! Some people even question their role in Amelia Earhart's death and dismemberment.

Coconut vs. Coconut crab: who will win??

Part of why the rumor of the coconut crabs' skull cracking ability persists is their sheer size: they are the largest land-dwelling arthropod, weighing up to 9 pounds!  They are related to hermit crabs, but ditch the protective shells after adolescence. For something that large, with a heavy exoskeleton, walking around on the ground is a pretty impressive feat. But they can also climb trees!

Can you imagine walking through the forest, minding your own business, and coming eye-to-eye with this guy!?! It would be so awesome!!

Monday, July 4, 2011

Happy Fourth!

Happy 4th of July!

I hope you are all having a fun and safe time celebrating the red, white, and blue!

Friday, July 1, 2011

My spidey senses are tingling!

Sorry I’ve been on hiatus a bit. What with my husband leaving for his Russian field season and friends coming up from the lower 48 (not to mention lab work!) it’s been a bit hectic at the Snow Crab Love HQ.

My friend John is a fellow Southampton College alum and a science blogger. (It’s hard to keep myself from singing every time I read his Chronicles of Zostera!) He dives around Long Island and takes phenomenal pictures and video. Lucky for us, some of his subjects are of the crabby variety! Check out this spider crab (Libinia emarginata, I believe) munching on a sea nettle:

Pretty cute, huh? These guys have a special place in my heart because I sifted through THOUSANDS of them during my lobster survey days. Plus there’s been so much work with these guys involving methyl farnesoate that I feel like I know ‘em inside and out!