Gene You're Positively Glowing!

Out on the beaches of the Pacific is a group of heroes. A squad of jiggly life savers, spending their days scanning the surf, waiting for their moment to pull you back from oblivion... 

What!? Oh God...NO. Get your head out of the gutter, uck! What the heck is wrong with you? I'm talking about jellyfish; specifically the water jelly (Aequorea victoria), they're also called crystal jellies and have many other common names, so for this post we'll just call them Aequorea (pronounced: ay-core-ee-uh). 

Just as much acting talent in this photo, as in the one above it.

Courtesy: Denise Allen via Flickr

Now we've often declared our love for jellies. In fact this isn't the first time they've appeared on Depth and Taxa. If you want to get a refresher on the jelly life cycle, and learn about one of Aequorea's cousins check out the older post here. But Aequorea are especially interesting thanks to their contributions to the field of medicine. You might be picturing some kind of Doogie Howser scenario with a jelly subbing in for Neil Patrick Harris, and you'd be right to want to watch that. But what Aequorea have provided for humanity goes beyond just caring for sick individuals, and making us laugh Tuesdays at eight on ABC.

At first glance Aequorea only possess a simple elegance. They're completely clear, and don't have particularly flashy innards like some species. The wagon wheel-like structure inside their umbrellas is a system of canals that distribute nutrients around the jellies' bodies. But radial canals are a basic part of jelly structure, so although they're pretty, they aren't particularly distinctive. To see what has made Aequorea so important to humanity we need to take the lights down.

Oh man, those damn ravers keep leaving their trash everywhere...

Courtesy: William Ward via The Encyclopedia of Life

That ring is the outline of the bell margin of an Aequorea jelly. The glow you see is naturally produced by the jelly itself. Interestingly, we don't know for sure why these jellies produce this light. They don't constantly flash like fireflies, nor do they glow continuously like the stage at a Deadmau5 show. For the most part we've only observed Aequorea glow after they've been jostled by a human. Even if we don't understand why Aequorea glow, scientists have spent a lot of time figuring out how they do it.

In the 1960's, while trying to isolate the glowing material from Aequorea jellies, Dr. Osamu Shimomura and his team determined that a pair of proteins is actually responsible for producing this jelly's light. The first in this dynamic duo is a molecule called aequorin. Aequorin emits blue light when it's exposed to calcium ions. The second protein, which produces that green fluorescent glow we see is called... green fluorescent protein. Points for clarity I guess. Green fluorescent protein, or GFP, only glows when exposed to light in the same spectrum as the light produced by aequorin. So first, calcium ions flow into the aequorin which flashes blue, then the blue light hits the GFP which absorbs it, and then the GFP releases some of the energy it absorbed as green light.

Okay so how is glowing protein helpful to medicine? Well it's what triggers the glow in these proteins that's important. See calcium is an important trigger in both the nervous and muscular system. Calcium ions flowing into nerves spark them to send out the chemicals that transmit information between themselves and the next nerve in the chain. Scientists can inject aequorin into the area around a nerve and figure out where and when the calcium is flowing to the cell by seeing when the aequorin glows! This is incredibly useful when studying nervous systems because you can actually observe a nerve functioning, which is normally an invisible process.

Aequorin being activated by a calcium solution.

So aequorin is pretty cool, but it's green fluorescent protein that has really changed the landscape of cell research. GFP normally absorbs the light from aequorin to glow, but will also absorb light from the nearby UV spectrum. So that same black-light you used to make that Bob Marley poster look so cool in your dorm can be used to peer into the chemicals that sustain life itself.

Scientists managed to clone the green fluorescent protein and ever since have been attaching it to other proteins to watch how they're made, where they go, and how long they last inside the bodies of different animals. Dozens of fluorescent proteins, in several colors, have been created from GFP and others have been found in animals like sea anemones. Mice have been genetically modified with GFP tagged normal cells and glowing red protein tagged cancer cells. When observed under black-light scientists can actually watch how the cancer cells grow and spread in real time without harming the mice.

The thing that makes GFP so powerful is that it can be added to almost any cell or protein. So if you have a question about how fetuses develop, tag an egg cell with GFP and watch it divide. If you want to watch nerves grow as a mouse learns, tag their brains with GFP, and see them think. If you want to release a bunch of infertile male mosquitoes into a population to eliminate malaria without pesticides. Tag their testicles with GFP so you can sort the boys from the girls, and get to sterilizing. All of these things have actually been done using modern genetic techniques and a variety of fluorescent proteins.

These are the nerve cells in a mouse's brain expressing different chemical signals.

You're observing this animal's brain tell its body how to function

Courtesy: ZEISS Microscopy via Flickr 

Okay so maybe it isn't Aequorea itself that'll save your life. Mostly they'll keep eating plankton and washing up on shore like they've been doing for millions of years. But if it weren't for Aequorea's development of GFP we would probably never have been able to discover all that we have about living things, especially our own bodies. Animals and plants shouldn't be protected and preserved solely for their potential usefulness, but if one of the least noteworthy jellies can single tentacledly spark an entire research industry; imagine what else we can learn from the "nobodies" on the tree of life.

References:

Nikon's Microscopy U,
Accessed via: http://www.microscopyu.com/articles/livecellimaging/fpintro.html

The GFP Site; From professor Marc Zimmer at Connecticut College.

Accessed via: http://www.conncoll.edu/ccacad/zimmer/GFP-ww/GFP-1.htm

Mills, C.E. 1999-present. Bioluminescence of Aequorea, a hydromedusa. Electronic internet document available at http://faculty.washington.edu/cemills/Aequorea.html. Published by the author, web page established June 1999, last updated January 11th 2009

Shimomura, O., "The Discovery of Aerquorin and Green Fluorescent Protein", Journal of Microscopy, Vol. 217 Pt. 1, Jan. 2005, pg. 3-15.

Accessed via: http://www.cooperlab.wustl.edu/PracticalAdvice/Shimomura2005.pdf

The Age of Sail

Oh boy are we going into the woods this week. For those who know me it's no secret that I love jellies (The squishy animals. I don't care much either way about the fruit spread.) So when IFLScience posted this article about by-the-wind-sailors, Velella velella  (dibs on the band na...oh) washing up in their thousands in Monterey bay I couldn't help but get excited. Not only because velella are incredibly cool, but because just explaining what they are is an odyssey of learning on its own. Incidentally this is one of the cases where using the scientific name is actually easier than the common one, so from here on I'll be referring to these animals as velella.

Hundreds of velella washed up on a beach. A surprisingly normal occurrence.

Courtesy Bettina Walter via Flickr

Now on the surface jellies seem pretty simple, and in terms of structure they are. They have no brain, their outer layers are usually one to three cells thick, and since they only have one hole in and out of their body; they eat and poop from the same opening. But jellies are one of those groups of animals that are so diverse and confusing they make a game of thrones family tree look like an elementary school ancestry project. In fact what we usually call jellyfish aren't even all the same thing. Let Steve Haddock from the Monterey Bay Aquarium Research Institute (MBARI) explain how there is no such thing as a jellyfish.

Seriously though MBARI has the best youtube channel

If you aren't able to watch that video it basically explains that so many different types of animals have evolved gelatinous forms that there isn't a great case for calling anything a jelly. In the interest of simplicity however when I refer to something as a jelly I'm talking about a tentacled, free-swimming life stage of either a scyphozoan, hydrozoan, or cubozoan. These three groups are classes of cnidarians (pronounced: nye-dairy-annes) which are animals whose tentacles have cells containing venom injecting harpoons. These stinging cells (called cnidocytes) are used partly for defense, but primarily  for prey capture. This is actually why humans can't feel the stings of many jellies; the relative size and sturdiness of their prey compared to the jelly determines how strong the sting needs to be. Jellies that prey upon fish, squid, and larger crustaceans need to make sure their prey is paralyzed or dead almost the instant it comes into contact with their tentacles. If  prey were to struggle hard enough it could do serious damage to the thin skinned, gooey jelly. Even though many jellyfish can't hurt you; I never recommend people touch them. So many types of jellies look similar to one another that it can be hard to tell the painful stingers from the harmless ones.

Especially the way most people find them.
Courtesy Justin Henry via Flickr

So where does the whole "tentacled free-swimming life stage" I mentioned fit into our story of velella? Well jellies have an astonishing life cycle. There are two completely separate phases to these animals. The phase we're most familiar with is usually what's called the medusa. Medusas have distinct sexes and reproduce when males release packets of sperm into the water which the females have to eat. Not only is there only one way into and out of the jellies, but the females' reproductive organs are inside their digestive track. Many species brood their eggs for a while holding them in their tentacles. From those eggs are hatched babies that will never become the free-swimming jellyfish. Instead they leave their mother's embrace and find a spot to settle on the bottom. Once settled they morph into their other major life stage; the polyp. Polyps usually look like very tiny sea anemones. They feed on plankton and detritus (particles of dead stuff) building up energy like a caterpillar. And like a caterpillar they go through a metamorphosis; not into an adult jelly but into a cloning machine. Entirely new organisms grow out of the polyps' bodies. This is the medusa that we know and love. It's like small frogs growing out of the side of tadpoles that never become the adult form! For you visual learners out there, below you'll find the life cycle in a beautiful chart. And in case you've been wondering what the difference is between the hydrozoa and the scyphozoa one big separator comes in the polyp stage. Scyphozoa divide their baby jellies in nice neat stacks whereas hydrozoa bud off all over their bodies.

"Reproductive cycle of jellyfish" by Zina Deretsky, National Science Foundation - http://www.nsf.gov/news/mmg/mmg_disp.cfm?med_id=65102&from=search_list. Licensed under Public domain via Wikimedia Commons

Okay, we've gotten a good understanding of what a jelly is and how their lives work so we can return to our friend velella. Velella is a type of hydrozoan who takes everything we just talked about and flips it the middle tentacle.

Oh my god he's doing right now right now!
Courtesy Andrew via Flickr

 Instead of having a polyp that sticks to the bottom velella has a polyp that sticks to the surface! That's right the beautiful sail-carrying jelly is the stage that does the cloning. For a long time it was assumed that velella was a special multi-polyp, colonial, siphonophore like the Portugese man-o-war Physalia physalis. In fact they look quite a lot alike and behave similarly. But studies now suggest velella is a pretty unique organism being one of only a couple animals in the porptid family. And it's not entirely clear whether the floating polyp is one relatively big individual, or a big shared float with a colony of clones underneath.

Okay, so if what we see is the polyp stage, where are the medusas? Well amazingly the medusas are tiny and when they bud off from the polyp they dive down into the depths. Just about everything about velella is backwards from what we expect. The medusas mate in the deep and their babies cruise up to the surface where they develop into the floating form. Velella polyps show differences in the orientation of their sails depending on where they live. In the center of ocean basins it's hypothesized that velella polyps have sails angled so they're carried both east and west. But closer to shore; polyps have sails oriented so prevailing winds keep them in the ocean.  When large storms or anomalous winds kick up they drive the velella on the water into the shore. And that's the source of Monterey's large stranding.

Velella has few threats to its continued existence so thankfully we can expect these amazing animals to be around for quite a long time. There is the possibility that the larger storms that come along with global climate change will cause more frequent strandings. So as always doing what you can to cut back on carbon emissions is a great way to help make sure the age of sail continues for these wonderful animals.

Sail on my friends, sail on.
Courtesy PowderPhotography via Flickr

References:

http://eol.org/pages/1006207/details

http://animaldiversity.ummz.umich.edu/accounts/Hydrozoa/

http://ocean.si.edu/jellyfish-and-comb-jellies#section_The_Stings:_Nematocysts_and_Colloblasts

K.J. Eckelbarger and R.Larsen. Ultrastructure of the ovary and oogenesis in the jellyfish Linuche ungiculata and Stomopolus meleagris, with a review of ovarian structure in the Scyphozoa. Marine Biology #114, 1992. Accessed via: http://link.springer.com/article/10.1007%2FBF00357260#page-2

http://animaldiversity.ummz.umich.edu/site/accounts/information/Velella_velella.html