Sleeping Beauties

Imagine yourself cruising down the road at night. There's no moon so, so you're driving slowly, peering into the blackness to find your way. As your eyes adjust you see a gigantic, ancient woman sidle into the glare of your headlamps. She's slow and battered, and moves almost as if she's in a trance. You slow down even more to avoid hitting her, but you can't bring yourself to get out of the vehicle. As she meanders to the edge of your lights' beam she turns slightly, and you catch a glance at her eyes. A tubular creature dangles from two filaments embedded in her cornea. Though she's surely been blinded by the parasite you sense that she can feel you there. As she's enfolded back into the darkness you wonder was she an ancient spirit? An aesthetic hiding away from society? A witch? or even a zombie?

She was a shark.

Courtesy: NOAA Photo Library via Flickr

In our imaginary scenario you're a researcher with the US' National Oceanic and Atmospheric Administration. You're cruising along in a submersible when a species of sleeper shark swims in front of your vehicle. 

There are only around six species of sleeper sharks that we know of, and two of them fit the bill for this story; the Pacific sleeper shark (Somniosus pacificus) and the Greenland shark (Somniosus microcephalus). Although their cousin the southern sleeper (Somniosus antarcticus), which lives around Antarctica and is so badass it eats juvenile colossal squid, comes close it doesn't fit our story because it isn't affected by the dangling parasite; which we'll talk about later.

Pacific sleeper and Greenland sharks are truly incredible. They're massive. Adults of both species average around 4 meters; that's about 14ft, but they can grow even larger. That size is on par with all the largest predatory sharks we're more familiar with. 

I'm gonna go ahead and guess this kid is not

the one who reeled in this shark

 Courtesy: Wikimedia Commons

Unlike great whites or tiger sharks, which are fast, active predators, sleeper sharks are sluggish. It's believed that they hunt by sneaking up on live prey. They move so slowly, about the same speed as a crawling baby, and are so hydrodynamic that they barely disturb the water. So when prey are distracted or at rest they don't notice these incredible predators. Not only can sleeper sharks hunt, but they're also effective scavengers. Researchers have found meat in sleeper shark stomachs that's crawling with the organisms that usually consume dead flesh on the ocean bottom. We also know from stomach contents that sleeper sharks will consume seals, dead whales, fish, and even polar bears! It's not clear if the polar bear was an individual that drowned while crossing sea ice or if it was taken live, but either way....wow. Even crazier, a couple of guys in Newfoundland, Canada found a stranded Greenland shark that had 2 feet of moose tissue stuffed down its gullet! 

Little Known Fact: Hastily gobbled moose is 

the national dish of Canada

Courtesy: Christian Heilmann via Flickr

Now this slow lifestyle has benefits besides giving sleeper sharks the ability to hunt or scavenge literally everything. Sleepers are found in cold waters, either at the poles or deep in the ocean. In fact, Greenland sharks are the only shark species known to live under the arctic ice cap. In frigid waters it's easier to survive with a slow metabolism because with a fast one you're constantly compensating for lost heat. Plus a slow metabolism means you can live for a really... really... really... really long time.

A study published in Science used radiocarbon dating of the core of Greenland sharks' eyes to predict the age of a variety of individuals. This technique suggests that really old Greenland sharks may be 272-512 years old! If that's the case they're the longest lived vertebrate on earth, and there are sharks alive today older than the United States. 

"Suck it Methuselah!"

Courtesy Public Domain via Encyclopedia of Life

The downside to growing to that great age is that sleeper sharks probably don't reach sexual maturity very quickly. It's been estimated from the development of ovaries and testes in dead sleepers that they can't reproduce until they're 10 or more feet long. Greenland sharks are thought to grow so slowly that they might need 150 years before they can get to baby making. If that's the case then these fish may be very sensitive to overfishing. Sleepers are commonly caught as bycatch in fisheries for other species, so it's very important to use programs like Seafood Watch to ensure your fish comes from sustainable sources.

In Iceland there is a small targeted fishery for Greenland sharks because they're the main ingredient in one of Iceland's traditional dishes. Hakarl is Greenland shark that's been fermented for several weeks. It has to be fermented because sleeper shark meat contains a lot of Trimethylamine-oxide; which is toxic. It's so poisonous that sled dogs, ravens, and a sea birds called fulmars have been described as getting "shark drunk" after eating too much raw shark. The symptoms include stumbling, respiratory depression, erratic behavior, and vomiting.

Pictured: Shark Drunk

Couretsy: Schroder + Schombs PR via Flickr

The Trimmethylamine-oxide probably helps protect sleeper sharks from the challenges of living in the deep and polar ocean. The chemical counteracts the protein dismantling effects of high pressure at depth, and works like anti-freeze to prevent the sharks body from locking up.

Okay so all of these adaptations make sleeper sharks a pretty good match for the woman in the creepy story from the introduction, but what was that bit about the parasites on her eyes? Well I'm both glad you asked and horrified that you reminded me.

Pacific sleeper and Greenland sharks frequently host the parasitic copepod (pronounced: co-puh-pod) Ommatokoita elongata. One study found that up 85% of Greenland sharks have these creepy-crawlies living on and in their eyeballs. The copepod, which is a crustacean related to shrimps and crabs, inserts a stud called a bulla into the shark's eye and just kind of dangles from it. As it swings there for its entire life the copepod feeds on the juices from the shark's eyeball. It also scratches the ever living heck out of the cornea as it moves around. It's no surprise that these copepods commonly blind their hosts. However, sleepers don't seem to be affected by blindness at all. It's believed that sleepers rely on their other senses so much that they don't actually need their eyes.

      

I propose the common name of the "Why-God-why-does-this-exist!? copepod"

Courtesy: Johnathan Wojcick via bogleech.com

While sleeper sharks are certainly bizarre, they're also a magnificent example of adaptation to challenging conditions. They're probably the longest-lived of all vertebrates, they know how to take their time and move deliberately, they enjoy a place of respect in the food web, and they survive adverse conditions every day. Not only that, but if you're a little loose with your Latin translation, Somniosus microcephalus means "sleepy, little face". That's pretty adorable for an animal most might not call a sleeping beauty.

References:

Borucinska, J.D., Benz, G.W., & Whiteley H.E., "Ocular Lesions Associated with Attachment of the Parasitic Copepod Ommatokoita elongata (Grant) to Corneas of Greenland Sharks, Somniosus microcephalus (Bloch & Schneider), Journal of Fish Diseases, 1998, 21, pg 415-422

Courtney, D.L., & Foy, R, "Pacific Sleeper Shark Somniosus pacificus in the Eastern North Pacific Ocean Inferred from Nitrogen and Carbon Stable-isotope Ratios and Diet", Journal of Fish Biology, 2012, 80, pg 1508-1545

Hulbert, L.B., Sigler M.F., & Huntsford C.R., "Depth and Movement Behavior of the Pacific Sleeper Shark in the North-east Pacfic", Journal of Fish Biology, 2002, 69, pg 406-425

MacNeil, et Al., "Biology of the Greenland Shark Somniosus microcephalus", Journal of Fish Biology, 2012, 80, 991-1018

Nielsen, et al. "Eye Lens Radiocarbon Reveals Centuries of Longevity in the Greenland Shark Somniosus microcephalus" Science, 2016, 353, pg 702-704

No Author, "Moose-eating Shark Rescued in Newfoundland Harbour"(sic), CBC News, Nov 21 2013, Accessed via: http://www.cbc.ca/news/canada/newfoundland-labrador/moose-eating-shark-rescued-in-newfoundland-harbour-1.2434102

Life, uh, Finds a Way

A few hundred years ago we believed that nothing could live in the deep sea. Even as our understanding of the world grew, in some ways we lost our imagination. We began to understand that the deep was incredibly cold, very low in oxygen, and subject to astonishing pressures. So we assumed that this environment was just too inhospitable . Boy were we ever wrong.

A mile and a half down (2560m), on the vent field of an active volcano.
Courtesy NOAA Ocean Explorer via Flickr

More and more, we're seeing that life not only exists in the darkness, but thrives. A few weeks ago we talked about animals up in the water that survive with little light, but now we're headed to the bottom. The above image comes from a deep sea hydrothermal vent community, which in the last few years has become relatively well known. Thanks to programs like Blue Planet and Planet Earth, there is beautiful footage of these ecosystems readily available to the public.

But hydrothermal vents are a small part of the ocean bottom. Other incredibly diverse ecosystems exist, and with the prevalence of the internet, researchers are starting to show them as they're discovered. Some of the coolest environments being found are cold seeps.

There are several types of cold seep ecosystems, but what defines them all, is gasses escaping from underground into the water. Seeps have been found all over the world, from as shallow as 15m (easily diveable) to over 7000m (not easily anything), and even in inland bodies of water. Generally seeps are found on the edges of continental slopes where the earth's crust is bending and folding. Unlike hydrothermal vents cold seeps are not due to magma heating seawater and expelling it back out of the ground. Seeps form in places where a lot of plant and animal matter has settled to the bottom, become buried, and decayed. As that material breaks down it makes a lot of methane gas. Then as the ground bends it squeezes the gas, pushing it closer to the surface through the soft sediments on top. My apologies for being crass, but yes, the earth does fart.


A stream of bubbles escapes from the ground at a cold seep
Courtesy Deepwater Canyons 2013 - Pathways to the Abyss NOAA-OER/BOEM/USGS

The gas alone is not enough to establish an ecosystem; some organism needs to harvest the gaseous bounty to start a food chain. On land and in the surface waters, plants convert the sun's energy into chemical energy using CO2. At cold seeps bacteria and archaea convert the energy in the methane (CH4) coming from underground, and sulfate in seawater, to a type they can use. In a spectacular bit of symbiosis the archaea manipulate the methane and the bacteria manipulate the sulfate, then they use one another's products to complete their energy conversion. The exact nature of this back and forth isn't well understood, but scientists do know it produces hydrogen sulfide.

The hydrogen sulfide is then used by bacteria living inside animals to produce even more energy. These animals (some types of mussels, clams, and tube worms) have little to no digestive system. They get their energy straight from their symbiotic bacteria. At many cold seep sites large mats of bacteria and archaea are surrounded by these animals. Sometimes they even form a bulls-eye of different colors radiating out from the center.


Bacterial mats (white) and mussels (brown/orange) thriving at a cold seep
Courtesy NOAA Photo Library via Flickr

These large sedentary animals draw in small animals that take shelter in the jumbled chaos of their shells. Predators of those small organisms then come hunting. Many animals also feed directly on the bacterial mats, so there don't even have to be larger organisms around them. Entire ecosystems develop from the toots of the planet. Some of the animals that take advantage of cold seep environments are even ones that we eat, like sablefish and crabs. King crabs have even been observed feeding on bacterial mats, leaving, and coming back only after enough time has passed for the mats to regrow!

All of this biological activity helps contain methane (a potent heat trapping molecule) in the sea, keeping the temperature of the earth from rising even more. Also many seeps found in very deep water have low enough temperatures and high enough pressures for solid ice crystals to encase methane molecules. These "methane hydrates" also help keep carbon out of the atmosphere. You can see the biological and geological carbon traps interacting in this adorable video below.



Cold seeps are a good number of deep sea ecosystems, but there's more talk about, and even more to discover. Clearly the ocean bottom isn't quite so lifeless as we once believed. And probably it's even more full of life than we currently understand. Jurassic Park's Ian Malcom knew what he was talking about.

References:

Levin, Lisa, "Ecology of Cold Seep Sediments: Interactions of Fauna with Flow, Chemistry and Microbes", Oceanography and Marine Biology: An Annual Review, 2005, 43, 1-46, Taylor & Francis

Accessed via: http://levin.ucsd.edu/publications/Levin%20OMBAR%2005.pdf

Niemann et al., "Methane-Carbon Flow into the Benthic Food Web at Cold Seeps- A Case Study From the Costa Rica Subduction Zone", PLOS ONE, Oct. 2013, DOI: 10.1371/journal.pone.0074894

Accessed via: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0074894#pone.0074894-Niemann1

"Discovery of a New Chemosynthetic Community" NOAA Ocean Explorer

http://oceanexplorer.noaa.gov/explorations/13midatlantic/logs/may8/may8.html

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