Travel With Crabs: Galapagos

It's time again to

My friends Torrie Behrens and Ben Penzick recently got back from an amazing trip to the Galapagos, and they couldn't wait to share their crab photos with us! (Really, they took a lot of amazing photos of a lot of awesome animals, but we'll just stick to the crabs here.)

Me: When were you in the Galapagos? Where did you actually get to walk around? 

Ben and Torrie: We were in the Galapagos the second week of April, 2012. Prime wet season in the Galapagos so there was a lot of breeding going on from all species and a lot of very small babies running around. We took a small capacity cruise to Baltra, Seymour, Chinese Hat, Bartholomew, Genovesa, Santiago, Rabida, Santa Cruz. Every tour operator's itinerary in the Galapagos is regulated by the park service and most is unseen by tourists. There are designated trails that tourists cannot deviate, luckily most of those trails are close to the shore, allowing maximum crab sightings.

including Sally Lightfoot crabs (Grapsus grapsus)!!!

What did you learn about the crabs you saw?

We learned that the Sally Lightfoot crabs are not endemic to the Galapagos, but can be found throughout the Americas.

crabs, on the rocks

Their coloration is used to attract mates and they're not born with those colors. Their colors vary a lot; I found the most with blue on their chests, and some had very brilliant blues while others were much more pale.

check out this crab's colors! so bright!

When the crabs are born they're a dark rock color which allows the young to blend in with their habitat.

a juvie Grapsus grapsus

They have a lot of predators in the Galapagos including the Lava Heron.

"Lookin' for crabs in all the wrong places." - lava heron

The crabs are not as fearless as most species in the Galapagos, our guide suggested it was because Herons cast a similar shadow of humans, of a different scale, and it makes the crabs scurry away.

They molt their carapaces when they need to grow (their shells do not grow with them) including their eyeballs! Once they molt, they back out of their previous shell and go into hiding because they need to allow time for their shell to harden. At this point, they're soft shell crabs. We also learned that Europeans do not eat soft shell crab!

 Ben with a "t-shirt" or molt

Torrie rockin' some crab fashion

Claws regenerate! (through the molting process: when they shed that hard shell, they can begin to regrow their missing limbs while soft, though it takes a few molts to regenerate fully)

They are able to move so well over rocks because they have two joints that function in different directions allowing full movement of each of their limbs.

mechanics of a molt's legs

The crabs share a habitat with the marine iguanas, and are often climbing right over them, which doesn't bother the iguanas at all.

sharing (space) is caring: it can be fun!

for whatever reason, this iguana cracks me up:
it looks so tiny next to that crab! 

[More crabs with animals!]

sea lion and surf

they even hang out with penguins! (see the red dots?)

What else did you see?

While traveling, we also saw Ghost Crabs that have eyes almost floating above their bodies. They lived in holes in the ground on the beach and would only come out if we were very still and didn't make any vibrations. And we saw freshwater crabs in the Amazon swamp, mangrove crabs along the coast, and various super tiny crabs along mainland Ecuador's coast and hermit crabs!

 a freshwater crab spotted in Ecuador!

Thanks, Ben and Torrie, for letting me share your photos and fun facts!

How does Ophilia grow?

Ophilia the opilio is back with another mini-book! This time you and your friends/kiddos/pets can learn how a crab grows: through the molting process.

It's a very simplified version of what goes down for our little crustacean friends, but you can learn more about the hormones involved here, the terminal (or final) molt in snow crabs here, growth through a succession of red king crab molts here, and watch a video of a spider crab molting below (it's pretty crazy!).

To make your new mini-book:

1. Just download this pdf and print it out.

2. Follow the instructions from the original Ophilia post.

Hooray!

3. Learn (or teach), color, and enjoy!

this guy worked really hard, but it paid off in just how big he was able to get!

NOAA's Sea Week

The last 3 weeks were "Sea Week" at NOAA's Ted Stevens Marine Research Institute. Hundreds of kids got to come through the labs and learn about some of the sea creatures that call Alaska home. I got to visit too (since I work there) and took some pictures to share with you!

 the touch tanks had many different animals:

snails, sea cucumbers, hermit crabs, and blue mussels to name a few

 two orange hermit crabs (Elassochirus gilli)

hanging with a sea cucumber (Parastichopus californicus)

I was smitten with this orange guy!

 "Oh dear, I've rolled over!"

 a beautiful blue friend

 a darker fellow (Elassochirus tenuimanus)

Hermit crab molt! You can see, because of their soft abdomen,

that the hard parts they have to molt are only on the 

front portion of their bodies! So cool! 

 there were also some sweet lyre crabs

and scallops! Can you see its many little eyes?

The scallops were a lot of fun because they are really quite active when they sense predators, like this large pycnopodia sea star:

I hope you enjoyed the virtual tour of TSMRI's touch tanks!

Can't blame your mom on this!

HAPPY MOTHER'S DAY!

We all have a lot to thank our moms for, but I know there are some out there who like to blame their moms for some things too. Like, "Don't blame me; I have my mother's sense of humor" or "I can't help it; I got my mom's lack of coordination" or "I'm getting my mom's butt!!!"

"I got my mom's pretty polka dots!" - Neopetrolisthes ohshimai

(OK, that's probably not the porcelain crab's mom,

but it definitely got the polka dots from someone)

It's no different for crab moms, but new research is showing that not all facets of baby crabs can be blamed on their moms. At this past year's Alaska Marine Science Symposium, two such studies looked at potential maternal effects on embryo quality, one in snow crab (Chionoecetes opilio) and the other in red king crab (Paralithodes camtschaticus).

"Eee! I'm a larval snow crab!"

Joel Webb looked at embryo size, dry weight, and chemical compostition (% carbon and nitrogen) in emryonic snow crabs to see if they varied depending on the size of their mothers. It's already known that multiparous mothers (those gals that have been around the block a few times) are more fecund than primiparous females (first-time moms). The question here was: will larger mothers make larger, healthier babies? He found that, for all quality measurements, there was little variation due to female size and shell condition. Ultimately, to answer his question: No.

Yay for opie moms!

Kathy Swiney looked at similar quality controls (size, weight, carbon and nitrogen content) from red king crab clutches. She also found that, while mothers may have been different sizes, the quality of larvae they produced was no different! (There were differences in carbon and nitrogen between years, but that's another story.)

(photos by Ben Daly and Celeste Leroux)

So there you have it: you may blame a lot on your parents, but if you're a crab baby, you can't blame your small stature on you mom!

You can read the abstracts from the link here:

Joel Webb et al.: Are all eggs equal? Maternal effects on embryo quality in the snow crab, Chionoecetes opilio. p. 162

Kathy Swiney et al.: Interannual and Seasonal Variability in the Size-Fecundity Relationship for Red King Crab (Paralithodes camtschaticus), with Considerations of Maternal Size effects on Embryo and Larval Quality. p. 64

perfect Crabday for moms

Mother's Day is right around the corner! Have you gotten your mom something yet? Flowers? A card? This week's Crabday crab??

Chocolate Swimming Crab

Thalamita spinimana

"I love you THIIIIIIIS much!" - chocolate swimming crab

If I know moms, then I know what moms love: CHOCOLATE! So I figured what better crab to talk about than a chocolate one? Well, really it's called the red swimming crab, but we all know how common names vs scientific names work, and this guy has a chocolate-colored appearance, so I'm going with it! (You can see the brown hues better at this site.)

a red specimen showing off his beautiful spots

These guys like to hang out in tropical reefs, and because they have those modified 5th walking legs shaped like paddles, they can swim around and catch their prey! They are so good at hunting that they've even been described as "vicious"! And we all know moms can be vicious when blocked from their chocolate gifts.

 nom nom nom

(check out his chocolate spots!)

Well done, crabs. Well done.

Travel With Crabs: Oahu

Our first destination is Oahu, Hawaii. My husband Adam had the opportunity to travel to Oahu and work at the University of Hawaii at Manoa lab processing Steller sea lion blood samples. When not working, he headed to Waikiki Beach and spotted these little guys:

A'ama

Grapsus tenuicrustatus

I love their green spots!

there are 4 a'ama crabs in this shot!

A'ama has several other common names including the lightfoot crab (kind of like Sally Lightfoots seen here) and the weak-shelled shore crab. They are an important crab to Hawaiians who enjoy catching and feasting on them either cooked or fresh and raw! To quote [a translation of] the song "E 'A'ama":

"Run, run, you must run away

Run, run, here and there

I will catch you, black crab
You are delicious!"

"I'd like to see you try!" - a'ama crab

Run these crabs will! They are built for running on land and in the water, and maintain different postures to gain greatest efficiency in either environment. That's why they are so fit for intertidal habitats and are often found on lava rocks ducking from the waves.

two crabs at a tide pool

Keep an eye out for these black beauties the next time you're in Oahu! And if you see a bright red version seemingly sunning itself on the rocks, it just may be a molt for you to treasure!

Run, a'ama, run:

Martinez, M. M., R. J. Full, and M. A. R. Koehl. 1998. Underwater punting by an intertidal crab: a novel gait revealed by the kinematics of pedestrian locomotion in air versus water. Journal of Experimental Biology 201: 2609 - 2623.

Martinez, M. M. 2001. Running in the surf: hydrodynamics of the shore crab Grapsus tenuicrustatus. Journal of Experimental Biology 204: 3097 - 3112.

Meet Sean's Crabs

I had the pleasure of meeting two very special, very sweet little crabs at my friend and fellow SFOSer's apartment: Snap and Ewan McGregor!

Snap (hunkered down - you can just make out his silhouette)

and Ewan (in the forefront)

I took lots of pictures and asked Sean Larson (sea otter/sea cucumber guy from this post) just as many questions. It went something like this:

Me: How do you tell them apart?

Sean: Ewan is the better looking one.

(Don't worry, Snap, I think you look great too!)

Me: Do you know what species they are and where they are from?

Sean: Gecarcinus quadratus, located from Mexico to Peru, but mine were from Costa Rica I was told!

Gecarcinus quadratus are known as the Halloween crab, 

the moon crab, and the harlequin crab
(among other common names)

True story: I thought these guys were a congener, zombie crabs (G. ruricola) until I double checked my own zombie crab post and realized I had misidentified one of my photos! I've since updated it, but I owe a big Thanks to Snap and E.M. for setting me straight! 

Me: How often do you feed them? What do they seem to prefer, if anything? 

Sean: I feed them every day, they usually wait until night to eat. They eat everything!!!! I have fed them lettuce, cabbage, potatoe, orange, banana, BACON and Dungeness crab. They like veggies but they LOVE meat. They ate all the crab I gave them last night; I was so proud.

Ewan eating bacon!

Me: Do they interact with each other much and are the interactions friendly or more competitive? 

Sean: They are pretty friendly, if I perturb them, then they kinda crawl all over each other. During the day, they kinda hunker down on opposite sides of the tank. But who knows, they may have little turf wars at night that I don't see. 

Me: Tell me more!!! 

Sean: They like to dig holes... each night there are new holes throughout the tank. I think that is because in the wild they dig into river banks and hide during the day and then come out at night to scavenge. 

(Read about hole digging behavior in Costa Rican G. quadratus here!)

Sean (cont.): Sometimes when I am sitting next to them at night watching a movie I can peripherally watch them slowly exit their holes and then I turn towards them, there is this awkward stare down for a minute before they either run back or keep moving. I am going to switch their day night schedule with a UV bulb so they are more active during the day.

(sorry this is so dark, but I didn't want to freak them out with the flash)

Sean (cont.): They never pinch, I can hold them.

Sean: "Yeah Crabs!"

Waiter, there's a crab in my bivalve: part 2

No, this is not another recipe for baked clams or crab-filled treats. This is much better!

Where the shellback crab lives in old bivalve shells for protection, there are other crabs that live in LIVE clams, mussels, oysters, etc!! That crab is the

Pea Crab

the polka dot pea crab (Pinnaxodes floridensis)

I was pretty excited when I learned about this guy (thanks Bryan!).  There are a few species with the common name pea crab, but, as far as my little research review went, they all have one thing in common: they hunker down in those comfy hinged molluscs!

"Of the small crabs that live in a foreign host"

(from Rondeletius (1554) courtesy of Haines et al. (1994))

Female pea crabs seem to prefer this lifestyle compared to the free-swimming male crabs, but mating pairs have been found in mussels! Because of this sexual difference in preference, the relationship between male pea crabs and their hosts is considered amensalism, which means one species has a negative effect on another, but with no effect to itself. The male pea crab may harm its mussel host, but it gets no real benefit from the mussel.

true story

Female pea crabs are simply parasites. Parasitism means one species benefits at the expense of the other species. Scientists saw negative effects to mussel growth when female pea crabs were present, so while the female pea crabs had a safe place to live, their mussel hosts were stressed and unable to attain similar lengths compared to unparasitized mussels.

"Hey! I'm livin' here!" - female pea crab

Bonus fun fact: pea crabs also parasitize sea cucumbers too! So if you're feeling like you want two snacks in one, keep an eye out for these little crabs on your next mussel/cucumber foraging expedition!

Pea crab papers:

Haines, C. M. C., M. Edmunds, and A. R. Pewsey. 1994. The pea crab, Pinnotheres pisum (Linnaeus, 1767), and its association with the common  mussel, Mytilus edulis (Linneaus, 1758), in the Solent (UK). Journal of Shellfish Research 13: 5-10.

Tablado, A., and G. J. Lopez. 1995. Host-parasite relationships between the mussel, Mytilus edulis L., and the pea crab, Tumidotheres maculatus (Say), in the southwestern Atlantic. Journal of Shellfish Research 14: 417-423.