Suspiciously Helpful Drifters

I can't contain it any longer! The blog has been active for three months now and we've barely talked about the most amazing, most important, most spectacular group of living things on the planet! Well no more. Prepare yourselves to meet the very reason for life on earth as we know it...

Oh look it's even waving hello

Courtesy Lindsay Waldrop via Flickr

Well not that specifically, that's just a baby barnacle, we'll come back to him/her (I'm not being politically correct, barnacles are hermaphrodites) in little bit. What I'm talking about is plankton. And I'm not exaggerating when I say that plankton are why we have the planet that we do. They've shaped evolution since the beginning of life, and they continue to do so today. So this week we're going to take some time to learn about our magnificent, mostly tiny, benefactors.

The word plankton itself has a pretty cool story. It comes from the same Greek word as planet, Planktos, which means wandering. Planets seen from earth look like stars and they do this weird thing where they kind of meander across the sky. Because of this, the ancient Greeks called them "wandering stars" in their own language. A couple thousand years later a German physiologist named Victor Hensen saw all these living things wandering on currents around the Baltic sea and gave them the name.

Another important part of plankton is the fact that it's not a term to describe how things are related to each other genetically. Saying something is plankton isn't like saying something is a mammal; it's more like saying it's a carnivore. The word describes behavior not biology. That's how algae (referred to as phytoplankton) and animals (called zooplankton) can both be plankton. Any living thing that is moved around by currents, tides, and waves more than it can move itself is plankton.

Pictured: Plankton

Courtesy Ian Sanderson via Flickr

That's right any living thing, so even giant jellyfish are technically plankton. Naturally being very small makes it a lot harder to resist the movement of water so the vast majority of plankton are pretty tiny. Sometimes this means that zooplankton are baby versions of the familiar species we find on the beach.

Take that baby barnacle that we met at the beginning for instance. He/she is a perfect example of meroplankton (they're plankton for merely part of their life). Gravid (the egg-laying version of pregnant) barnacles launch out those tiny babies when they hatch. The babies are then free to spend the next couple weeks cruising the currents eating and growing strong; before settling down to stay in one spot for the rest of their life. These baby, or larval forms as they're known, are actually really important for scientists trying figure out how animals are related to one another. We thought barnacles were related to snails until the mid-1800's when we had good enough microscopes to see that the larvae are more like shrimp.

Of course just because something is small doesn't mean it's a baby. Many living things are plankton permanently. These are called holoplankton (they're plankton for their whole life) and they are incredibly important to the ocean's food web. The two classic examples of this are copepods (pronounced cope-uh-pods) and krill. Both are crustaceans, just like the barnacle, and between the two of them they directly or indirectly feed almost everything in the ocean.

 A copepod (on the left) and a krill (on the right), you've probably seen them in TV and Movies

Courtesy NOAA Great Lakes and Norkrill via Flickr

What these two groups of animals lack in size, they make up for in numbers. Around Antarctica alone it's estimated there are around 500 million tons of just krill! One krill weighs about seven tenths of an ounce. There are literally uncountable numbers of these animals in the ocean. There are so many that we get into numbers that human brains actually have a hard time comprehending. You start to understand how something as massive as baleen whales can live off these two animal groups almost exclusively.

So zooplankton are clearly important to the health of the oceans, but what about the algae, those phytoplankton from before? Well we wouldn't have things like krill and copepods without those phytoplankton, and in fact we probably wouldn't have ourselves either. Like plants on land phytoplankton are at the bottom of almost every ocean food chain. They take sunlight and carbon dioxide and turn it into sugar, which things like krill and copepods love to eat. So the copepods gobble up the phytoplankton, and then they're gobbled up by fish, and on and on, all the way up to you. When you eat a fish you're eating everything that fish ate, plus everything that fish's prey ate, plus everything that fish's, prey's, prey ate. It starts to look pretty important to keep the plankton's tiny ecosystem healthy doesn't it?

Not only do phytoplankton make life work because they're food for other living things, but they provide complex life with something extremely important. Go ahead and take two really deep breaths for me. Nice, long, slow, relaxing breaths from your diaphragm. Feels good doesn't it? All that fresh oxygen to your brain and muscles really does you good. Well amazingly the oxygen in one of those breaths came from phytoplankton.

"You're welcome!"

Courtesy NOAA Photo Library via Flickr

It's been calculated that about half of the oxygen in the earth's atmosphere comes from the ocean. That means that phytoplankton are at least as important as all the terrestrial forests, all the savannahs, and all the shrub lands, combined. Remember how I mentioned that we can't even count the number of krill or copepods? Well to make that many animals you need even more of these algae. There are so many phytoplankton in the ocean that they actually dye huge swathes of the ocean green during the summer, which can be seen from space! Not only does phytoplankton sustain us complex organisms, it's partly responsible for us being here in the first place. 

On the very ancient earth most of the oxygen in the atmosphere was tied in with other gasses, like carbon dioxide, and what was escaping, quickly came out of the air to rust the metals in rocks. But then a group of photosynthesizing bacteria evolved multi-cellularity. All of a sudden there were way more organisms using up the CO2 and dumping out a lot more oxygen than the rocks could absorb, and BAM! They created an atmosphere full of an element that's essential for biological processes in animals.

So that's it for this week. I could write even more about plankton: how they have the single largest migration on earth, how they provide food for the deep ocean with their poop, and I will eventually; but for now let's just appreciate the incredible, essential plankton by looking at this wonderful picture of a spring bloom in the Atlantic.

For scale: that's Ireland at the top middle. This is a real color photo

Courtesy NASA Goddard Space Flight via Flickr

 References:

Carefoot, Tom, "Learn About Acorn Barnacles", A Snail's Odyssey. 

http://www.asnailsodyssey.com/barnacle.php

Sessions et al. "The Continuing Puzzle of the Great Oxidation Event" Current Biology 19, 2009, DOI 10.1016/j.cub.2009.05.054, Accessed via: http://web.gps.caltech.edu/~als/research-articles/2009/sessions_et_al_2009.pdf

Shirrmeister, et al., "Evolution of multicellularity coninsided with increased diversification of cyanobacteria and the Great Oxidation Event." Proceedings of the Natural Academy of Sciences, vol. 110 no. 5, pg. 1791-1796, DOI 10.1073/PNAS.120992710 Accessed via: http://www.pnas.org/content/110/5/1791.full

Krill Facts Center, International Health and Science Foundation

http://www.krillfacts.org/

Drop the (Antarctic Research) Bass

Exterior shot: Antarctic research station over the Ross Ice shelf. Except for a single lamp right outside the door it's the complete inky blackness of the southern winter. Motes of snow billow past through the light and we hear only the sound of rushing wind. The camera slowly zooms in on the entrance. Cut to Interior: Two researchers, a man and a woman, are settling onto cots. There's a dull orange glow from the lamp outside over everything. The woman looks over to the man.

Woman: I can't believe how quiet it is here. Back in Seattle I got so used to hearing the noise from the street that I'd forgotten what it's like in the field.

Man: Yeah everybody reacts a little differently. Some people love the isolation, others start to go a little nuts, start to think they're hearing things. Either way all you'll be hearing for next couple months is wind and creaking ice, so get used to it quick. 

Woman: I'll be fine, I've had enough of civilization lately. I'm ready for the silence.

Man: Good. I wouldn't want you going cracked on me with just the two of us down here. Let's get some rest.

They both settle into their cots and rest their heads on their pillows. The camera pans across the room and settles on the woman's face. She looks slightly unsettled, but calm as she slowly closes her eyes. The camera lingers on her face and all sound from outside dissapears, suddenly we hear this:  

  

And our heroine's eyes snap open! End Scene.

While that may sound like the first scene from yet another reboot of The Thing it's a situation that can actually happen in Antarctica. As ruined by the image on the clip; that sound is not an alien horror, nor the intro to the latest club sensation, but a cuddly seal. (Disclaimer: No wild animal should ever be cuddled, seals have no way of knowing that your hug isn't a grip of death and they will defend themselves, also they usually smell like fish and pee.) Specifically that sound comes from the Weddell seal (Leptonychotes weddellii) which breeds farther south than any other mammal. And they'd have the record for all animals too if it weren't for those meddling penguins. They were first reported on the ice above the Weddell Sea but they have what's called a circumpolar distribution. Basically that means they're found all the way around Antarctica on coasts and ice shelves.

Weddells live much closer to shore than the other Antarctic seals. Although they generally prefer shallower water Weddell seals have been found diving 600 meters down in search of prey! To give you an idea of how far that is, the deepest dive ever done on SCUBA equipment was only half as deep (332m Ahmed Gabr). While it may not be noticeable to us there is a big difference in ice real estate for Weddell seals.

Perfect example; no one wants a bedroom right next to the road
Courtesy Sandwich via Flickr

 Breeding age females and males hang out on ice closer to land than juveniles. The ice closer to shore is called fast ice because it's locked fast and doesn't shift around much. On the ocean side is the more familiar pack ice which gets packed onto and removed from the sheet pretty regularly. As you can imagine a constantly shifting environment isn't great for rearing babies. There's some contention among scientists as to whether or not the adults migrate from the fast to the pack ice, but it looks like most Weddells are pretty site specific.

One of the lines of evidence for this is the presence of the sounds you heard earlier. The trilling noise is unique to male Weddell seals. That sound is thought to be a territorial display since males use it all year round, but ramp up how often during the breeding season. Of course it's always possible that these seals just really love Doctor Who. Either way we know that, during the breeding season, males guard cracks and holes in the ice that females use to access the water.

How you doin'?
Courtesy Sandwich via Flickr

Of course those holes in the ice are also very important for breathing. Even though they can go without fresh air for up to 80 minutes at a time, being mammals means they still need to breathe between dives. In fact both male and female seals put quite a bit of effort into keeping the holes open. Fast ice has fewer gaps than pack ice, so the ones that are free need to be maintained. Weddell seals use their teeth to literally carve out thinner sections of the ice.

It's easy to assume the seals would keep breathing holes to themselves but they've been seen sharing these spaces. So scientists think that some of the underwater vocalizations are seals communicating about the breathing holes. Decoding the Weddell seals' language requires a lot further study; but it could be that seals approaching the surface are letting those already on the ice know they're coming, or seals at the holes telling those underwater where they can be found.

Weddells are the most well studied of all of Antarctica's seals, but we still know so little about them. Why do they have up to 30 different vocalizations? What are they trying to say? Do they get more inspiration from Depeche Mode or Daft Punk? Thankfully, Weddell seals have been relatively unaffected by the loss of ice in Antarctica so far, so there's lots of opportunity to learn the answers to these questions.

References:

Weddell Seal (Leptonychotes weddellii), Wildscreen Arkive

http://www.arkive.org/weddell-seal/leptonychotes-weddellii/image-G53852.html

Leptonychotes weddellii: Weddell Seal, Encyclopedia of Life

http://eol.org/pages/328638/details

Doiron et al. "Proportional underwater call type usage by Weddell seals (Leptonychotes weddellii) in breeding and nonbreeding situations." Canadian Journal of Zoology, 2012, 90(2): 237-247, 10.1139/z11-131

Lake et al. "Spatial utilisation of fast-ice by Weddell Seals (Leptonychotes weddellii) during winter.", Ecography, Vol. 28 Issue 3 pg 295-306,  June 2005, DOI 10.1111/j.0906-7590.2005.03949.x 

Lighting Up The Deep

Happy just after Halloween everyone! And Feliz Dia de los Muertos if you're in Central America! This is one of my favorite times of year, not least of all because I've always had a lot of fun on Halloween. It's one of those few holidays that stay awesome no matter how old you get. When you're young you get to have all the fun of trick-or-treating, and when you're older you get to have parties. I remember one of my favorite things about trick-or-treating was getting to use glow-sticks.

Yeah these things!

Courtesy Timo Newton-Syms via Flickr

Most of the time we humans get to glow for fun, but there are animals in the ocean that glow entirely to survive. So this week we're going to explore some of the beauty of deep sea bioluminescence.  

As I'm sure you know the further down you go in the water the darker it gets. Eventually you lose all light but for a long ways, up to about 1000 meters, small amounts of light still get through. Not all light is created equal though. Different colors have different wavelengths, and therefore have different amounts of energy. Colors like blue and green are very energetic compared to colors like red and orange, so they travel farther through the water. Many a scuba diver can tell you that you don't have to go that far down before everything becomes awash in only blue. This property of light is very important to animals in the deep sea, because it determines what color their bodies are and what  colors their bioluminescence. Watch the video below and see how many different colors of animal made light you can see.

Also, revere the master David Attenborough!

So how many did you count? I'm guessing maybe two if you've got really good eyes or like to be pedantic about blue vs. blue-green. So why do we see basically one color down there? Is the deep sea just racist? Well it comes back to those properties of light; blue literally goes a long way down this far. Communication is one of the important uses for bioluminescence in the ocean and you can signal over a much longer distance with blue light.

Alright so attracting prey and communicating with your own species is a great use for bioluminesence, but there's more you can do with living light. Believe it or not many animals use light to blend in. Even though this seems counter-intuitive animals that do this are using an extension of matching their background like traditional camouflage. Many animals in the region where a little bit of light still lingers, sometimes called the twilight zone, have light emitting organs called photophores on their bodies. The photophores give off the same color of blue that makes it through the water, breaking up their silhouette and blending them in. This is especially true when they're viewed from below because the light comes down from the surface. Many animals do this: from the incredibly numerous lantern fishes (Myctophiformes), to one of my favorite animals, the firefly squid (Watasenia Scintilans) 

Seen here in a festively appropriate form. 

Actual pictures can be seen here.

Now that we know the things most animals ocean animals do with biolumiescence, let's look at an interesting exception. Three genera (one grouping less specific than a species) of dragonfishes (Stomiidae) have photophores that make red light instead of blue. These special light organs, which are just beneath their eyes, actually beam ahead of them like headlights. The reason they use red instead of blue is two fold. One, most animals in the deep have no reason to see red. Dragonfishes' prey evolved in an environment where red light doesn't exist, so they have no need for the eye proteins that see it. And two, many deep sea animals are red. Weird right? But red is great camouflage against everything except for those three groups of dragonfish. Since there isn't any red light, animals with red skin appear completely black in the depths. These three genera of dragonfish are pointing lights that their prey can't see at animals that are lighting up like beacons.

Why are you weirded out? Only two of them have no bottom on their jaws.
By Erich Zugmayer (died 1939) [Public domain], via Wikimedia Commons 

Even more amazing is the fact one of the species in this group of fish, the Northern stoplight loosejaw (Malacosteus niger), regularly eats copepods (open ocean relatives of shrimp) which eat a bacterium that makes a type of chlorophyll that picks up red light. The stoplight loosejaw takes this chlorophyll and produces the pigment its eyes need to see red light. Think about that for a second; this fish uses the food, of its food, to make what it needs, to find food. Cue the theme song from Inception!

BWWWWWWAAAAAAAUUUUUUGGGGGHHHHHH!

References:

Douglas et al., "Enhanced retinal longwave sensetivity using a chlorophyll-derived photosensitizer in Malacosteus niger, a deep-sea dragon fish with far red bioluminescence", Vision Research, Vol. 39 Issue 17, Aug. 1999, DOI 10.1016/S0042-6989(98)00332-0, Accessed via: http://www.sciencedirect.com/science/article/pii/S0042698998003320

Moser, H. Geoffry & Watson, William, "Order Myctophiformes: Blackchins and Lanternfishes" From NOAA, accessed via: http://web.archive.org/web/20011201063212/http://www4.cookman.edu/noaa/Ichthyoplankton/Myctophiformes1.pdf

Malacosteus niger: Northern Stoplight Loosejaw, Encyclopedia of Life
http://eol.org/pages/224918/details

Watasenia scintillans: Sparkling Enope Squid, Encyclopedia of Life
http://eol.org/pages/399186/details

They're in the Trees Man!

It's autumn here in the Northern hemisphere, and in the Pacific Northwest many of our salmon species are making their return to the rivers they were born in. This amazing phenomenon has been well documented on TV, but there is an incredibly cool piece to the story that's often missing. One that weaves the ocean, the river, and the land together and shows us that nothing is alone in the environment.

Pacific salmon are a pretty cool group of fish, but honestly it can be really hard to agree on just what the heck a salmon is. This confusion comes from old terms for the same fish doing different things. Ever noticed how salmon and trout look almost exactly the same on the outside? Well that's because they pretty much are. All trout, salmon, char, freshwater whitefish, and graylings are part of the salmonid family. Amazingly many of these fish can spend their entire lives in freshwater, or they can spend part of it in fresh and part out at sea. Fish that have a life cycle which takes them back and forth between salt and fresh water are called anadromous (pronounced an-ad-row-muss) fish. Weirdly enough some species have a freshwater exclusive and an ocean going form, and they get different common names because of it. For example a rainbow trout (Oncorhynchus mykiss) lives in freshwater exclusively, but a steelhead (also Oncorhynchus mykiss) goes from fresh to salt and back again. It's genetically the exact same fish, but because steelhead fill up on tasty ocean plankton they get much bigger and their meat turns a lot pinker.  

"I haven't decided which I want to be yet. I'm taking classes in both and seeing which I like more."

Courtesy Ingrid Taylar via Flickr

Honestly the rest of this post could be about what is and what isn't a salmon, but that can get tedious and there's other things to get excited about this week. In general when people talk about Pacific salmon they're referring to one of five different species, which are all in the genus Oncorhynchus which means hooked nose. These are the coho (O. kisutch), pink (O. gorbuscha), chum (O. keta), chinook (O. tsawytscha), and sockeye (O. nerka). Aside from being many species instead of just one, Pacific salmon differ from Atlantic salmon (Salmo salar) by being terminal spawners. After they reproduce all five of the species listed above die. When I first learned this it seemed so sad and pointless to me. After all Atlantic salmon don't die after spawning, but it turns out the deaths of the adult Pacifics bring enormous amounts of nutrients into inland environments. 

"It's cool birds, I wasn't using my eyes anyway."

Courtesy Lewis Kelly via Flickr

When thousands of salmon flood a stream and die there, their bodies begin to decay in the water, but look at that picture above. Where's the shore? That fish is lying out in the middle of the woods. Even if the shore is just off camera a few feet I guarantee that fish didn't have "walk on land" as part of his bucket list. So how'd he get there? Well the answer is probably a bear. 

Bears are good swimmers, they love the fattiness of salmon, and they don't mind scavenging on rotting food. Bears and other animals drag salmon away from the streams to munch in peace and the parts they don't eat mix into the soil. Then plants in the area pick up those nutrients and use them to grow. One study found that trees without salmon nutrients grew about 2/3rds as fast as those with them. So trees are, through salmon, taking nutrients from the ocean and using them to grow; and there are salmon streams that are as far East as Idaho (That's 450 miles in a straight line from the mouth of the Columbia River.) where oceanic nutrients can be detected in the trees. It's not just the trees either; studies have found oceanic nutrients in the shrubs, ferns, insects, birds, amphibians, fish, and mammals of these environments. 

No wonder we call him the King

Courtesy spappy.joneS via Flickr

The way we know know this is pretty cool too. Scientists use isotope analysis to see how much of a certain type of Nitrogen is inside the trees. You can kind of think of isotopes as sub-species of atoms. They're not all unique enough to warrant calling them something else, but they often behave a little bit differently. Different environments favor the production and preservation of different types of each atom. The ocean, as it happens, is very favorable to the form of Nitrogen that has an extra neutron. So researchers are able to burn samples from the trees and use a cool device called a mass spectrometer to figure out how much of their chemical composition came from the ocean. At one site in Canada they found that in some years up to 80% of the Nitrogen available for Sitka spruce (Picea stichensis) came from those years' salmon runs.

It's become increasingly clear that salmon are important for the health of Pacific forests. And the implication is astonishing. If we want healthy trees, that grow more rapidly, create more diverse habitat, scrub carbon from the atmosphere, and produce more lumber, then we want healthy salmon. Amazing large scale projects with that goal in mind are already happening, and keeping salmon streams healthy is as easy as making sure you pick up after yourself when you visit a river. It may be a long time before we see anything close to historic runs again, but so much is being done on every level of the community that I'm confident we can make a difference.

If that seems hard to believe, remember all of these trees are partly made of fish.
The world is way weirder and cooler than we ever expect it to be.
Courtesy ArkanGL via Flickr

References:

"Family Salmonidae: Salmons and Trouts", The Burke Museum online

accessed via: http://www.burkemuseum.org/static/FishKey/salmon.html

Reimchen, Tom, "Salmon nutrients, nitrogen isotopes and coastal forests", Ecoforestry, Fall 2001.

Accessed via: http://web.uvic.ca/~reimlab/reimchen_ecoforestry.pdf 

Reimchen et al. "Isotopic Evidence for Enrichment of Salmon-Derived Nutrients in Vegetation, Soil, and Insects in Riparian Zones in Coastal British Columbia.", American Fisheries Society Symposium, XX: 000-000, 2002

Moore, J, & Schindler, D, (2004) "Nutrient export from freshwater ecosystems by anadromous sockeye salmon (Oncorhyunchus nerka) Canadian Journal of Fisheries and Aquatic Sciences, Vol. 61, 2004

Underwater Basket Weaving

Hey everyone, this week we're diving into a bit of a mystery. There's a pretty good chance that by now this little gem has come across your social media feed!

The original of that video had 8 million views on facebook alone last I checked. I've gotta say it's really cool that people are so curious about ocean animals. But the question on everyone's mind seems to be, as my mom succinctly put it: "What the heck is it?" Despite its facehuggerly appearance this is a native of the earth, or should I say the sea? What you're looking is a basket star. I should also mention that I'm not the first to identify this guy/gal. Both the Echinoblog, and IFLScience have tackled this mystery.

First off basket stars aren't actually a true sea star. You may remember from the post on catch connective tissue that sea stars are members of the echinoderm phylum. More specifically the sea stars we're most familiar with make up the asteroidea class (a class is one grouping more specific than a phylum) So if you're feeling pedantic and mischievous you can tell people you found tons of asteroids on the beach and not be lying. However the basket star is not an asteroid! Basket stars are part of a class of animals called ophiuroids (pronounced "off-yer-roids), and are more commonly called brittle stars.

 Jazz Hands!

Courtesy  Paul Thompson via Flickr

Even though most brittle stars look quite a bit like traditional sea stars, being in a separate class means they are as different from a true sea star as a sea urchin is. One of the most notable differences between sea stars and brittle stars is in how they get around. Sea stars use their hundreds of suction cup tube feet to grip tightly to the bottom and cruise along. Their rays (also referred to as arms) act as more of a platform for those strong tube feet to operate from. Brittle stars don't use their tube feet to walk. Instead they pick themselves up on their rays and stroll or slither like something out of the Nightmare before Christmas. Their tube feet lack suction cups and are used to grab food and help move it towards their mouth.

Basket stars are a really cool specialized group of brittle stars. They are well adapted for collecting plankton out of the water with their arms. In the above video you can only catch the view for a second, but at one point the basket star opens all its arms, and you can see the central disk. The disk is pentagonal and one trunk-like arm grows out of each side. Each of those five arms then branches dozens of times to create a wide net. The arms of the basket star are covered in microscopic hooks, a nice coating of mucus, and are capable of coiling around themselves to form traps that hold onto their planktonic prey. Below you can watch as some euphasiid shrimp are added to a basket star's tank at the Seattle Aquarium.

That video is a little sped up, but you can see how those branches form a wide net and are waved back and forth to sweep for more food. Grabbing food out of the water like this is called suspension feeding. Sometimes you'll hear it called filter feeding, but that's a bit different. When there isn't an obvious load of plankton around them, basket stars usually cling to a hard surface or the branches of corals. They curl their rays up above their bodies into the current forming a basket shape. Hence the name.

What a basket ca...I'm not even gonna let myself finish that joke

By Peter Southwood (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Once a basket star has enough food trapped on one of their rays they'll slowly move it towards their star shaped mouth. Incidentally brittle stars don't have an anus, so they excrete their waste through the same hole they consume food. Anyway inside the mouth are five sets of comb-like teeth. The star slides its arms over the teeth and the prey are scraped off like frosting from a fork. Am I the only one who does that? I can't be the only one who does that.

Basket stars are found throughout the world from shallow water to the abyssal plane. The one from the original video is probably Euryale aspera which is a shallow living basket star found throughout the Indian ocean and tropical western Pacific. One of the things I think is coolest about basket stars is that they seem to have a strong association with a variety of coral species. Not only do coral branches make a good holding place for adult basket stars, they may even be an important nursery for juveniles. Young of the species most commonly found around N. America, Gorgonocephalus eucnemis, are usually found living just inside the polyps of the sea strawberry coral (Gersemia spp.). While this seems to be some type of symbiotic relationship, it isn't entirely clear if the little basket stars are stealing food from the polyp they're living on, or just using their mouth as a platform to feed from.

References:

Stöhr, S., O’hara, T., & Thuy, B. (March 2nd 2012) “Global Diversity of Brittle Stars (Echinodermata: Ophiuroidea)” PLOS ONE DOI: 10.1371/journal.pone.0031940,
Accessed via http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0031940

"What is that weird thing on facebook???" The Echinoblog
http://echinoblog.blogspot.com/2014/10/what-is-that-weird-thing-on-facebook.html

“Gorgonocephalus eucnemis” Encyclopedia of Life, 

http://eol.org/pages/599654/details

"Gersemia” Encyclopedia of Life, 

http://eol.org/pages/41391/details

Sympathy for the Devil Fish

In case you've never heard the Rolling Stones song Sympathy for the Devil; go ahead and watch this video. Not only will having the song in your head make this post make a lot more sense, but it's also one of my favorite songs of all time.

Below you'll find the Depth and Taxa version of the lyrics. There's some ambiguity as to which animal I'm talking about, so see if you can figure it out before the end.

Please allow me to introduce myself
I’m a fish with planktonic taste
I’ve been around the whole wide world
Swum many a mile ‘cross the wastes

And I went  down to Africa
From the Azores, out at sea
Made the trip on currents

WOO! WOO!
Courtesy Grant Bishop via Flickr

that pushed me ‘long, and let me feed

Pleased to meet you
Hope you guess my name
But what’s puzzling you
Is the fact that I’m so tame

We’re all ovo-vi-vipar-ous
When we know that it’s time, to give birth
Got a real long gestation

Often times, it’s two years

My bat like wings
Are the perfect things
For the heaving seas
That I slowly swim

WOO! WOO!
Courtesy Kevin Bryant via Flickr

Pleased to meet you
Hope you’ll guess my name, oh yeah
Ah what’s puzzling you
Is the fact that I’m so tame, oh yeah

I made the list
When your scientists
Noticed the decline
Of this group of mine
Men shouted out,
“Look at those devil horns!”
When really they
Are ce-pha-lic fins

Let me please introduce myself
I’m a fish of planktonic taste
And I’ve been trapped in big drift nets
Who just write me off as their bycatch

WOO! WOO!
Courtesy William Warby via Flickr

Pleased to meet you
Hope you guessed my name
But what’s puzzling you
Is the fact that I’m so tame

Pleased to meet you
Hope you guessed my name, oh yeah
But what’s confusing you
Is the fact that I’m so tame

Just as all true seals are the phocidae
And all the squalids, sharks        
We're devil rays
just call me Mobula
Cause I’m in need of some defense

So if you catch me
Have some courtesy
Have some sympathy, and instinct
Use all your well-learned fishing tricks
Or I’ll end up, gone extinct, oh yeah

WOO! WOO!
Courtesy Patrick Neckman via Flickr

Pleased to meet you
Hope you guessed my name, oh yeah
But what’s puzzling you
Is the fact that I’m so tame

So did you figure it out before the end? The animal is, of course, the last image: the giant devil ray (Mobula mobular). I hope you enjoyed the different format this week. If you have questions, or you'd like a little bit more traditional post about these beautiful fish, let me know in the comments!

References:

"Skates and Rays" The Shark Trust

http://www.sharktrust.org/en/skates_and_rays

"Mobula moblar: Devil Ray" Encyclopedia of Life

http://eol.org/pages/213344/overview

Skin Deep

A calm ocean can seem uninteresting from above. At first glance it's this big expanse of basically nothing, but just beneath the surface lie wonders. The same can be said of sea stars. When we find them at low tide sea stars barely move. Many people aren't even sure that they're animals, and we regularly had people at the touch-pools of the Seattle Aquarium ask if they were fake.

 Well he does exaggerate how much he can bench, but I wouldn't call him fake

Courtesy Jerry Kirkhart via Flickr

  Right under the surface of sea stars, and the other echinoderms like sea cucumbers and urchins, lies what I think is one of the coolest adaptations of any animal on earth: catch connective tissue. This material is the source of echinoderms' amazing ability to become completely rigid, or jello soft.

Before we get into the meat of how this stuff works let's think about how it might be useful. At any one time different sections of a star's body can be rock hard, near liquid, and everything in between. This is an amazingly good strategy for an animal that moves over uneven terrain. Imagine you're a sea star and you're trying to find a tasty mussel to eat. As you crawl along your leading arm comes into contact with a big boulder. Well no big deal, you can make that arm go soft and bend to any angle you might need to climb onto it. As you reach the top of the stone you notice a strong current trying to blow you away. Again no problem, you can make a couple of arms go rigid to add strength to your grip which keeps you from waving around. Once you're held on nice and tight one of the arms that you're not using to cling for dear life can go soft and tap around the rock's surface in search of prey. Below you can see sped up video of a blue linckia star (Linckia laevigata) moving, and you can get a good idea of what I'm talking about. Check out how flexible the sections bending around the edges of the coral are, and how stiff the parts on the flat.

 Clearly this catch connective tissue is some useful stuff, but how does it work? In humans, our skin and connective tissues are made up of fibrils (small bundles of strands that make up a fiber) of collagen held together by connecting proteins.

Collagen fibrils (the big strands going up) and the proteins holding them together

Courtesy Zeiss Microscopy via Flickr

This is true for catch connective tissue as well.  The difference is that we have a more or less set amount of proteins holding the fibrils together whereas echinoderms can change the number of links. The more proteins holding the fibrils together, the less they can slide around on one another, and the more rigid the whole tissue. The fewer the proteins, the more the fibrils can slide around, and the softer the tissue. It's almost like bundling sticks with rubber bands. In what might be the greatest naming ever, the molecules that trigger the hardening and softening of the tissue are called tensilin and softenin. Many echinoderms can even reduce the number of proteins so low that they can literally walk away from sections of their body. This is called autotomy (dibs on the band name) and it's a great way to escape predators that might do much more damage by ripping off one of their appendages. Thankfully echinoderms have incredible regenerative abilities, so they can regrow parts of their bodies. There's a wonderfully quirky, yet easy to understand, video explanation of this incredible tissue at creaturecast.org.

References:

Ana R. Ribeiro, Alice Barbaglio, Cristiano D. Benedetto, Cristina C. Ribeiro, Iain C. Wilkie, Maria D. C. Carnevali, Mário A. Barbosa, (September 14th, 2011) "New Insights into Mutable Collagenous Tissue: Correlations between the Microstructure and Mechanical State of a Sea-Urchin Ligament" PLOS ONE, DOI: 10.1371/journal.pone.0024822 Accessed via
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0024822

Yasuhiro Takehana, Akira Yamada, Masaki Tamori, and Tatsuo Motokawa, (Jan 15, 2014) "Softenin, a Novel Protein That Softens the Connective Tissue of Sea Cucumbers through Inhibiting Interaction between Collagen Fibrils" PLOS ONE. 2014; 9(1): e85644.
Published online, DOI: 10.1371/journal.pone.0085644,
Accessed via http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3893245/

Dunn lab and Creature Cast
http://creaturecast.org/archives/2457-creaturecast-echinoderm-skin