Sunday, September 28, 2014

Getting Ston(ey)ed with Coral

We're Back! The new Depth and Taxa headquarters (AKA my apartment) is all set up with a fancy desk and everything. Thanks everyone for your patience during my moving process. So without further ado let's get back in the swing of things.

There was some great news that came out of the US National Oceanographic and Atmospheric Administration (NOAA) last month. Twenty coral species have been listed under the Endangered Species Act. "What? That's horrible, more corals are at risk of extinction!" you might be saying, but listing as endangered actually benefits many animals that are at the brink. When organisms are imperiled by extinction listing them serves to provide legal protections for, not only them, but also their ecosystems. It's kind of like a silent alarm going off. When someone breaks in, property is at risk, but once the alarm goes off; the police can come and take steps to keep you from being burgled. It's about time we got serious about protecting coral too. Whole reefs are in danger of disappearing. One study suggests that coral cover in the region between Asia, Australia and Hawaii has decreased by 20% since just the early eighties.

So why do we care? Coral is certainly very pretty, but it's also a fascinating and essential organism.

Seen here being all three at once.
Courtesy Ian Robertson via Flickr

Coral is a massive and incredibly old group of animals. In fact just about anything you think of as ancient, corals were there for its beginning: Megalodon? Coral bemoans its short time on the planet. Dinosaurs? Yeah coral thought they were cool for a while. Coelocanths? They're just trying to steal coral's old-timey charm. What I'm getting at is that coral shows up very early in the fossil record, something like 480 million years ago!

So what's the secret to coral's success? Well diversity is a big part of it. There are something like 2,500 coral species on earth today. They can be hard, soft, individual, colonial, small, large, tropical, temperate, shallow, and deep.  The corals we're most familiar with, and all of those recently added to the endangered species list, are the shallow-living stony corals we like to brag about snorkeling among when we take a trip to the tropics.

All corals are a part of the cnidarian phylum which you may remember from the earlier post about jellyfish.You might also remember that the scyphozoa, hydrozoa, and cubozoa have two life stages: the free-living medusa and the stuck-on polyp. Corals are part of the anthozoa which are all the animals that have no medusa stage.

Perseus can get behind an animal that removes the medusa. (I will not apologize for this terrible joke)
Courtesy Wally Gobetz via Flickr

What stands stony corals out from other members of their phylum is their structure. Unlike sea anemones or jellies; stony corals actually secrete a skeleton. Coral that you might find at a jeweler's, or on the beach, is in fact the skeletal remains of a stony coral. So your beach house may have skeletons in its closet as well as on its coffee table. These skeletons, made of the same molecules as eggshells, are what allow for the gigantic reefs seen in tropical waters throughout the world. And amazingly every reef starts out as a single teeny-tiny coral polyp.

See when a coral mommy-daddy and daddy-mommy (many stony corals are hermaphroditic) love each other very much, and the season and tidal phase are right, they pour floating packets of sperm and eggs out of their bodies and into the water. It's all very romantic as thousands of other animals circle the waters around them devouring their genetic material before it even has a chance to mix. But luckily there are so many of these gamete (reproductive cells) balloons that some do make a new baby coral. At this point in their life baby corals are called a planula, they're microscopic, and they're covered in little cellular oars that allow them to move and find a place to settle. As they settle, baby coral metamorphoses into its adult form, but its still incredibly tiny and all alone. So our intrepid hero begins making itself some friends, by cloning.

"I'm pleased...we're's nice to meet you"
Courtesy Nhobgood via Wikimedia Commons

Each of those little anemone looking things up there is a clone of a single polyp that settled on a hard surface. If the entire colony is very large, then the original polyp probably settled decades ago. Some head's of coral have been estimated to be over a thousand years old! This slow growth rate is one of the reasons many coral reefs are at risk of extinction.

 Amazingly, although the clones are separate individuals from the other polyps they all share body tissues with one another. As the polyps catch prey with their stinging tentacles and eat it; the nutrients from that food are actually spread across the shared tissue so that the whole colony benefits. These shared tissues are also what secrete the hard skeleton of stony corals. And it's inside the corals' shared tissues that we can find the reason for their stony skeleton.

Just beneath the skin of stony corals lives one of a number of different algae. These single-celled seaweeds, called zooxanthellae, (pronounced zo-zan-thell-ee) are taken in by the coral deliberately because they can benefit one another greatly. The algae is protected from the thousands of mouths out in the plankton and the corals' wastes make great fertilizer. The coral also benefits because the algae's photosynthesis provides oxygen and nutrients both of which the coral can use. So the coral creates this elaborate skeleton in part to reach for the sun. The skeleton acts like the trunk and branches of a tree pushing the coral and its algae buddies towards the light. The constant competition for sun is what has driven the evolution of so many amazing forms and shapes of different corals.

Enough sun salutes to make a yogi weep for joy
Courtesy US Fish and Wildlife via Flickr

 This mutual symbiosis has been going on for so long and is so beneficial that some coral species can't feed themselves without their zooxanthellae. When people talk about coral bleaching this is what they mean. Something has gone wrong in the ecosystem, so the algae have either gone elsewhere or died. Leaving only skeletons behind. Luckily you can easily help prevent bleaching if you visit tropical areas. Danovaro et. al discovered that synthetic sunscreens actually encourage the growth of viruses that infect and kill zooxanthellae. So when you take that snorkeling trip make sure to use non-synthetics like titanium dioxide or zinc oxide. Often times these sunscreens are labeled as "coral safe" or "sensitive skin" so they're easily found.


Danovaro et. al, "Sunscreens Cause Coral Bleaching by Promoting Viral Infections", Environmental Heatlth Perspectives Apr. 2008: 116(14): 441-447. Accessed via

Hoover, John P. "Hawai'i's Sea Creatures: A Guide to Hawai'i's Marine Invertebrates", pg 46-49, Mutual Publishing, 1999

Monday, September 8, 2014

The Punkest Fish in the Sea

Dust off your record player, whip out that old Sex Pistols vinyl, and get moshing because this week we're talking about the punkest fish there is: the rock-mover wrasse.

"Oi, Oi, Oi!!!"
Courtesy Steve Dunleavy via Flickr

Rock-movers, also called dragon wrasses (Novaculicthys taeniourus), are a tropical fish found all throughout the Pacific and Indian oceans. So how is it punk? A better question would be how isn't it? But you wouldn't know that would you poser!? 

First off; just look at that thing. That is the single most rockin' mohawk in the history of evolution. Not only does it have two giant fans on its head, the dorsal (back) and anal (you can probably guess) fin have adapted into mohawks too. It's also patterned like someone used a cigarette to put burn holes in a national flag and then splashed whitewash across it. There's that subdued and tasteful green background with the orderly, geometric, brown, dividing lines; and then a bunch of random white splotches ringed by black. These adaptations allow juvenile rock-movers to pretend they're drifting dead algae that's full of holes. Yeah they dress as trash. Throw a safety pin on there and you've got the whole look locked down.

I'll be honest I'm not sure I remember which picture is the fish...
Courtesy Ken Tam and Trip & Queball via Flickr

Of course it's not enough to dress punk. If you don't want to get called out as a poser you've got to act punk too. When rock-movers are put in aquariums while they're still small, other fish will often pick on them. However once they size up a bit and get confident they'll take on virtually everything around them. They establish a territory and guard it against any and all comers; I mean literally too. I was first introduced to this fish in an open top tank behind the scenes at an aquarium. I leaned over to look in, and a rock-mover shot out from the coral and charged the surface. A four inch fish tried to take on a 6 foot human because I looked at him funny.

In the wild rock-mover wrasses can be found living above sand and coral rubble between reefs. These fish deliberately live in the broken waste between the closest things the ocean has to cities. That is hardcore as s**t. They constantly toss rocks and coral rubble around  (hence the name) even building them into forts which they can sleep under. Now fancy "educators" and "scientists" might try to tell you they lift the stones to look for invertebrates underneath that they can eat, but we all know they're really practicing putting bricks through windows. Sometimes rock-movers will channel all their teen angst at once to lift rocks nearly as heavy as themselves or bury completely.

Best watched with Anarchy in the UK playing in the background

But there's one final nail in the coffin for this being the most punk fish in the sea. Something that's an essential stage in the punk lifecyle. They totally grow out of it. See the crazy flamboyant colors and appendages are just a phase. Every picture I've shown you so far has been a juvenile. Eventually like any punk; rock-movers settle down, put on some more practical fins, and have a couple hundred kids.

Though they might go to an occasional Alice Cooper concert
Courtesy J.E.Randall via EOL


Thursday, September 4, 2014

A Worm as a Weapon

One of the things I love about the ocean is that every separate surface is its own ecosystem. If you look at the shell of a crab you're likely to find plants and animals growing there. And that's just the ones that don't deliberately decorate themselves. Many times the organisms living on and around each other form some kind of symbiotic relationship. As you probably remember from school, symbiosis is when two organisms live together and can affect each other's behavior. Often times we say that both benefit one another, but that's only one of three types. Mutually beneficial symbiosis is conveniently called mutualism. You've probably already heard of the symbiosis where one organism benefits and the other is harmed; it's called parasitism. Finally when one organism benefits and the other doesn't get anything but also isn't harmed it's called commensalism.

All three types are frequently observed in this environment 
Courtesy Canyon 289 via Flickr

Chris Mah, who is an awesome scientist and blogger over at the Echinoblog did a post in 2010 about a team of scientists who took a closer look at a cool symbiosis. You can read it here. In his post Dr. Mah talks about how we thought that the banded scale worm (Arctonoe vittata), which lives on a number of invertebrates in the Pacific northwest, probably didn't benefit its host organisms. Consequently they are generally considered commensals. However a team of scientists decided to see if one of the worms' hosts, the leather star (Dermasterias imbricata), preferred to have a worm over not. If they did prefer to have the worms it would suggest the worm benefited the star and would actually be a case of mutualism. Well it turns out the stars chose worms over nothing, other stars, and even their favorite foods! The scientists who wrote the paper offer suggestions for how the worm benefits the star, but also recommend looking into it more. I'd like to offer the video below as evidence of the worm's benefit to the star.

That is the same banded scale worm biting the hell out of a sunflower star's (Pycnopodia helianthoides) rays. Seriously the worm looks like the love child of a graboid and a xenomorph when it chomps down. In this case the worm is protecting a keyhole limpet (Diodora aspera). As far as I'm aware sunflower stars don't eat leather stars, but the morning sun star (Solaster dawsoni) consumes pretty much everything; especially other stars. Solaster dawsoni is such an invertebrate killer that it's also commonly called the vampire or death star.

Oof!  The leather star is probably not gonna regenerate from that one.
Courtesy Brooke Reiswig at:
Clearly the leather star could potentially benefit from the predator warding prowess of the scale worm. Wouldn't it be cool if the scale worm also occurred on morning sun stars so they could be protected from one another, because they're totally cannibalistic!? Oh wait they do!

Courtesy same as above

 That specific worm could be jumping ship from the star being eaten, but banded scale worms have been documented living on morning sun stars. Obviously no scientific rigor has been applied to this hypothesis yet, so it may turn out to be a load of hooey, but it's exciting to look at evidence and begin to form questions. I hope we'll see a study or some video evidence of stars also being protected in the future.