long lost family members

When you think of lobster relatives you probably picture crabs and shrimp, not cockroaches and dragonflies. But it turns out that they may be more closely related than we originally thought! Researchers recently came together during the Society for Integrative and Comparative Biology meeting to discuss a reorganization of the family tree. Basically, instead of insects and crustaceans being separate branches, they may be part of the same branch called 'Pancrustacea':

This special symposium was co-organized by my Master's advisor friend, Sherry Tamone! In the past, researchers have noticed similarities between insects and crustaceans, but their methods for studying them differed. There are more genetic resources for insects while crustacean researchers focus on hormones (like me!). But, using this symposium as an example, they're coming together to find similarities. Take methyl farnesoate and insect juvenile hormone: they control growth and maturation in crustaceans and insects, respectively, but are inactive in their arthropod counter part. The link is that production of both are limited by the same enzymes!

sesquiterpenoids represent!

As Sherry says, "We should get comfortable eating crickets. It's all one big group." You can read more in Science and check out abstracts from the symposium here.

FA!

No, not a long long way to run. (I'll wait for people to get that. Got it? Good.)

FA stands for farnesoic acid, and I've been running it in the lab to make sure that what I'm looking at in my snow crab hemolymph truly is methyl farnesoate (MF) and not FA. (Remember, MF is a crustacean reproductive hormone. I'm hoping to quantify levels of MF in various groups of snow crab males to see how the terminal molt affects their reproductive physiology.)

FA is the precursor to MF. See how similar they look?

two sesquiterpenoids: MF (top) and FA (bottom)

see how they compare to the insect juvenile hormone III here

For more fun, long, sciencey words: MF comes from FA through the methylation of the latter, which is catalyzed by farnesoic acid O-methyltransferase (FAMeT)! Thrilling I know.

The good news is, after running different levels of FA through the HPLC, I am ever the more confident in my MF results! Yay for anagrams, and yay for me!

Yes, Tina Turner, you had a question?

"What’s methyl farnesoate got to do, got to do with it?

What’s methyl farnesoate, but a sesquiterpenoid?

What’s methyl farnesoate got to do, got to do with it?

Who needs a heart when you’ve got mandibular organs?"

Wow, that's a good question Tina (or three, really). I'm surprised you're so familiar with crustacean hormones, but I guess I should never underestimate Ms. Turner.

mm-hmm!

Well, now that I've been set straight, let me answer your big question: what does methyl farnesoate (MF) have to do with crab love? That is the big question in my graduate thesis, and I'm afraid I don't have all the answers... YET. But here's what I do know:

You'll remember that MF is synthesized in the mandibular organs (MO):

methyl farnesoate leaving the mandibular organs and heading for the gonads

When the MF leaves the MOs (ah, science and acronyms), it binds to specific receptor sites that can change the physiological activity of the target (such as the gonads). What results is increased gonad development, so far recorded in these crustaceans:

monsoon river prawn Macrobrachium malcolmsonii (pictured is a congener)

and red swamp crayfish Procambarus clarkii

green crab Carcinus maenas,

Indian field crab Oziotelphusa senex senex (another congener picture),

and spider crab Libinia emarginata

In the red swamp crayfish, green crab, spider crab, and Tanner crab (you remember Chionoecetes bairdi), higher MF also correlates with more reproductive behavior. And, since MF stimulates secretion of ecdysteroids by the Y-organs (which in turn stimulates the production of a new shell and shedding of the old one), mating and molting are hormonally linked!

MF stimulating the secretion of 20-hydroxyecdysone (20-HE) from the Y-organs

My research will look at the mating/molting relationship in snow crabs: will MF be lower in post-molt males? Will it correlate with lower gonads (GSI)? I can't wait to find out!

So you see, Tina, MF has a lot to do, lot to do with it!

It's a bit early for Halloween...

… but what the heck!

Methyl farnesoate (MF) is a sesquiterpenoid (5 syllables… try to use it in a haiku!) hormone, meaning it has a 15-carbon skeleton.

Methyl farnesoate's carbon skeleton. Get it??

It is produced in the mandibular organs which are glands, kind of like our pituitary gland. It is the crustacean reproduction hormone, but the tricky thing about it is that MF is also related to the insect juvenile hormone. What does that mean? When a juvenile crustacean, like a crayfish, has a high level of MF in its system before molting, it WON’T molt to a mature/reproductively active state. It will stay a juvie. It’s like your average 13-year-old boy (or 23-year-old boy…): hormones raging, but still basically an infant.

Hormones can be fun!

Part of this research project is measuring reproductive hormones in male snow crabs. But who really cares about mating hormones? The answer is YOU, especially when you were in high school.

in the year 2000

Crabs are just like people (OK, maybe not) in that they have glands that produce hormones, and these hormones then travel around their bodies affecting physiology and behavior.

Think of your pituitary gland and all the amazing things it's done for you (and for that guy from The Relic). Crabs have something similar: the X-organ sinus gland (XO-SG; see fancy drawing). Just as the pituitary gland controls the function of other endocrine glands, the XO-SG controls (by inhibiting) the function of the mandibular organs (MO) and Y-organs in crabs. And just as the pituitary gland produces follicle-stimulating hormone (FSH) to stimulate the ovaries and testes of humans, the MO produces methyl farnesoate (MF) to stimulate gonad development in crabs!

See, we're so similar!!