The hagfish, also known as a snot eel, is without a doubt the slimiest, slipperiest scavenger of the deep. Hagfish fall into the class of fish called agnatha, meaning jawless. As the name suggests, they lack jaws, but have two rows of sharp little teeth, perfect for taking a circular bite out of flesh. They use these formidable little chompers not only to eat the carcasses that fall to the bottom of the sea, but also to latch onto dying animals. They love to eat things from the inside out, worming their way into dead bodies before bursting forth in all their fattened slimy glory.
Each hagfish can generate up to 5 gallons of slime individually. Photo credit dirtsailor2003 at Flickr.
They are also incredibly good at squeezing through tight spaces too. Some researchers found that hagfish can squeeze into places that are half of their body width. How do they achieve it? Their skin is not tightly attached to their muscles, meaning they can actually redistribute the blood in their bodies to make one portion of their body slimmer while another expands!
What makes the hagfish most famous, however, is why it is often called a snot eel. When touched or grabbed by a predator, the hagfish secretes a thick white mucus out of over 100 glands on its body. One hagfish can produce a little more than 5 gallons of mucus at once. This serves as a pretty good deterrent for other fish that try to eat them; the mucus clogs up their gills and makes it hard to breath, choking them a level of slime old school Nickelodeon would be proud of.
If the slime isn't enough, hagfish can physically tie themselves into knots since they lack a spinal column (you can see the not if you jump to about 1:00 in the video below, taken from Nautilus Live footage).
I am a huge Buffy the Vampire Slayer fan, and whenever I see these fish and the way they can choke things with mucus, I can't help thinking of the horrid Queller demon from season 5. The awful thing crawls over people at night, clogging up their throats with slime as it leers over them with teeth of a lamprey, the hagfish's close cousin. If you don't believe me, look at the slime, look at these teeth, and then look up the Queller. It's the stuff of nightmares, and that's why these slimy fishes make it into my lineup of creepy critters.
The teeth of a lamprey, also an agnathan related to hagfish. Photo from Wikipedia.
It lurks in the darkness, barely seeing, barely moving, feelers outstretched, searching for its next victim. The hapless fish will be dragged beneath the sand, maybe in one piece, maybe split in two. With one of the creepiest methods of catching prey, the sand striker, also known as the Bobbit worm, Eunice aphroditois, gets my vote for one of the scariest animals in the sea.
For most people, looking at the Bobbit worm is enough to freak them out, but let's get into the details of why this animal makes me squirm.
The worm can grow up to 10 ft long, hiding almost all of its body underneath the sand while its head pops up above for feeding. It may be the longestpolychaete worm on the planet.
The worm senses fish with its outstretched feelers and by seeing the shadows as they swim by. When a fish gets close enough, it strikes quickly, grabbing its prey with deadly force that sometimes breaks the backbone of the fish and can split it in half!
If the strike doesn't kill the fish, the worm injects a venom which kills it and helps the worm digest it.
It can eat fish that are much larger than its mouth. Check out how it takes down a lionfish!
With all of these crazy elements going for it, this worm is no stranger to the tabloids. Take its name, for instance. The Bobbit Worm was named by Dr. Terry Gosliner after a trip to the Phillipines where he saw the worm. At the time, the Lorena Bobbit case was making headlines. When Lorena found out her husband was cheating on her, she cut off his penis while he was sleeping and threw it in a nearby field. When Gosliner saw the powerful jaws of the nocturnal sand striker and the way it sliced through the backbones of fish, it reminded him of Lorena Bobbit's evening revenge. Since then, both lady and worm have attracted a sort of morbid fascination.
This worm also hit tabloids in England when it found its way into the Newquay Aquarium. Aquarists were baffled as several fish turn up injured or disappeared, and especially when they found some of the coral in the tank sliced clean through. When the aquarists took apart the tank looking for the culprit, they found a 4ft Bobbit worm, which they named Barry. It is assumed he must have entered the tank with the coral when he was just a small larvae. While they originally thought Barry too ugly to display, the international attention he gained led them to put him in his own tank where a curious public could see him.
So, as Halloween approaches, would you dare take a peak? Do you think the Bobbit worm is one of the coolest, scariest animals in the sea?
A great white shark. Photo Credit Terry Goss on Wikipedia.
For the first time in over 80 years, someone has died from a shark attack on Cape Cod. It's a terrible tragedy, and one that will have people nervous to dip their toes in the water. As we have heard about great white sharks returning to the Cape in greater numbers than before, the area has had to decide what it means for tourism, for humans, for the environment, and for the future. With the return of sharks, we have seen a rejuvenating ecosystem, a snippet of the ocean returning to a healthy balance it is designed to have. People can bemoan the return of the sharks, but we know exactly why they have returned to the Cape: seals.
Right now grey and harbor seals are thriving on Cape Cod, but there was a time when the species' future was threatened in New England. The seals used to be routinely hunted, with a bounty even offered in Massachusetts of $5 per seal. They were seen as a nuisance, stealing fishermen's catch and taking up beach space. This, however, all ended with the Marine Mammal Protection Act in 1972. While it has been difficult to estimate exactly how many seals are now in New England, the numbers have clearly increased, and the grey seal population in Nova Scotia, which can spill into New England, is reported to have grown "exponentially." In New England, the seal population may have tripled. This is great news! It is a tale of protection enabling recovery of a species at a time when so many animals are struggling. It also means a boost in the economy for those in the tourist industry. Seals are a crowd pleaser, and boats that offer seal watching have been selling out. Since animal populations are often linked to others, however, the recovering seal population has helped other animals recover. Enter the great white shark.
A seal is a perfect meal for a great white. It's thick layer of blubber, meant to keep it warm, is a fat delicious meal for a shark. With increasing numbers of seals, more sharks can eat and survive, and that is what we are seeing happening on the Cape. Regardless of the seal's protected status, it's one of the reasons tourists are encouraged to stay away from seals and not swim with them. Swimming with a seal puts you in a shark's version of a buffet. It won't be looking for you, but it could find you anyway.
According to the Cape Cod Commission, about 5.23 million tourists visit the Cape annually, with 65% showing up in the summer months. That's about 3.4 million people coming to the Cape every summer. Presumably, a large number of them visit the beach at least once. This is the first fatal attack in 82 years, meaning the odds of dying from a shark on the Cape are insanely low. Chances are, however, these kinds of numbers won't alleviate the fear people feel when they hear about a shark attack. We hear that traveling by plane is one of the safest methods of travel, and yet many of us still get queasy when we are up in the air.
Seal sunbathing on South Monomoy Island. Photo credit Keith Shannon from
the US Fish and Wildlife Service on Wikimedia Commons.
Right now, we are seeing the results of our actions. Years ago, we decided to make an investment in protecting the ocean by protecting seals. This action has been incredibly successful. The fact that not only the seals have increased but that sharks have increased is a sign that the ecosystem is returning to a healthy balance. With the exception of us humans, great white sharks are at the top of the food web. The fact that the ecosystem can support sharks shows a kind of robustness that is good news for the smaller species involved as well, the kind that we may be fishing and eating. But what it does mean is that we have to be conscious about sharing the ocean. We can decide where to swim and how to do it, but sharks have no choice but to be in the sea.
The good news is that there are people actively having this discussion every day and working with local people and businesses to find the best way to share the shore. The Atlantic White Shark Conservancy focus on sharks specifically in New England, while OCEARCH tags sharks and tracks them around the world. They even create Twitter accounts for some of their sharks like Hilton, keeping people up to date on the interesting places the sharks swim to. It's an important reminder that while we only hear about sharks when there is an attack, most of a shark's life has no direct human interaction.
If you are still concerned, here are some things to keep in mind the next time you visit the seashore:
Never swim where you see seals.
Stay closer to shore, wading only up to your waste.
Swim in groups.
Do not swim at dusk or dawn.
In the unlikely event that you see a shark coming toward you, punch it in the nose. Seriously. Their noses are very sensitive and the sharks aren't looking for a fight.
Look for signs. At beaches on the Cape where sharks have been spotted, the Atlantic White Shark conservancy posts notices and advice about keeping yourself safe. Follow it.
Did you say shark? Photo Credit Andrew Reding at Flickr.
Most of all though, remember that you are not on a shark's menu. A great white wants a fat, juicy, blubbery seal. Finding you would be a bony and ultimately unsatisfying mistake for the shark. Most shark bites are simply that: a mistake. Ultimately, a shark wants nothing to do with you. With that in mind, try to enjoy the beach.
The humble sea star, beloved by many, symbol of tide pools, and... victim of a horrific melting disease? Yes. In fact, when it comes to sea stars, truth is stranger than fiction.
Healthy sea star
Here are some of my favorite things about sea stars:
They have an eye at the end of each arm. You can actually see it if you look closely enough; it's a tiny little black dot. They don't see like you or I do, but they can sense light. If you close your eyes, turn towards the sun, and then wave your hand in front of your face, you can see the shadow of your hand passing over your eyes. This is a bit like how a sea star sees.
Sea stars have to cling to rocks tightly so that they don't get tossed by the waves. In order to do this, they actually create a glue that sticks to the ends of their thousands of tiny feet. They also make a chemical that will dissolve the glue when they want to pick up their feet again. They can make and undo a glue that works underwater at will!
Sea stars are voracious when it comes to eating mussels. In fact, they eat so many mussels that if they are removed from an area, mussels take over the rocks so that nothing else can live there. Without sea stars, tide pools fail to exist as we know them.
The way that sea stars eat is like something out of a horror movie. When they find a mussel, they wrap their arms around it and pull from all directions until the mussel is too tired to stay closed and opens up. When this happens, the sea star spits its entire stomach outside of its body and digests the mussel inside of its own shell.
Because sea stars eat so many mussels, they became early enemies of fishers. To try to get rid of them, fishers would drag them on the boat, cut them in half, and throw them back into the ocean. What they didn't know was that sea stars can regenerate, so by throwing the sea stars back into the water, they had actually managed to make twice as many sea stars!
So what's up with this wasting disease?
If you are a bit queasy, you may want to skip the upcoming pictures. What comes next is disintegration, decay, and ultimately death, but it is the last step to befall the ill-fated sea star that picks up this mysterious condition. On both coasts, sea stars are literally wasting away. One day they are perfectly normal, bumpy, slow moving animals eating mussels to their hearts' content. The next day, there might be a small lesion on the outside of the animal. The following day, it may have lost some of its legs. The following day, all of its legs may be walking around on their own, completely disconnected from the sea star and spilling their insides behind them. Next comes death. The entire sea star can literally fall apart within days, and yet we still don't know why. That's why this phenomenon is called Sea Star Wasting Syndrome (SSWS). A syndrome is a mysterious medical ailment for which we don't have a clear explanation or treatment. This syndrome is no joke either. Researchers examining one species of sea stars in southern California, Pisaster ochraceus, found that, in some of their study sites, 99% of the sea stars died. That is truly astronomical; it's a tiny, local extinction. While the west coast, stretching from Baja California, Mexico to Alaska, has been impacted most by SSWS, sea stars on the east coast of the US can get it as well.
P. ochraceus with Sea Star Wasting Syndrome. Taken by Alisonleighlilly.
This is not the first time that sea stars have wasted away. There were mass die-offs of sea stars in the 70's, 80's, and 90's, but nothing on this scale had been seen before. The current blight was first discovered in a survey of the sea stars P. ochraceus in Washington state in 2013, although the disease affects many different species of sea stars. For a while, the cause of the disease was completely unknown, but in 2014 a team of scientists proposed that the disease was caused by a densovirus. The interesting thing about the virus is that it could be found in samples of sea stars collected in 1942, suggesting the disease may have been around for decades before this disaster.
So what changed? One of the leading theories is that temperatures in the ocean got really warm. Warmer temperatures can physically stress animals out, making them more likely to get sick, and ocean temperatures were unusually high in many areas where the outbreak of SSWS was most severe in 2014. Scientists in the lab also saw that adult sea stars in warmer water died faster than sea stars in colder water. In addition, young sea stars were more likely to get sick in warmer water.
The disease can first appear as lesions, followed by legs that fall off of the main body, leaving gaping wounds. The legs seem to have a mind of their own after, crawling around trailing innards behind them. The central circle of the body may be left, with the legs spreading to the far corners. When the pieces dissolve, all that is left are small, white spines, but not before the decaying arms of the sea stars have left a bitter, rotten smell behind.
However, this doesn't explain everything. One study found that decreasing water temperatures could help sea stars live longer, but it didn't necessarily stop them from getting sick. Another study looking at the original outbreak in 2013 found that water temperatures were not particularly warm when the disease first emerged. Another theory was that if there were a lot of sea stars densely packed together, they would be more likely to get sick, but a lot of the places hit hard by SSWS did not necessarily have a lot of sea stars to begin with. Finally, although SSWS may be caused by the densovirus, there still isn't conclusive evidence that that is the cause. This leaves scientists with a pile of questions and very few certainties on which to build a plan for protecting sea stars.
The arms can dissolve at different rates. This arm was still moving, but you can get a good view of the circulatory system.
The picture I just painted looks very grim, but there is actually a lot of reason for excitement and optimism. In a recent study, scientists found that the number of new sea stars that survived each year increased 74-fold between 2012 and 2015. In addition, there seems to be a genetic shift in the population to sea stars that are more resilient and don't get the disease as easily. Basically, the disease killed off sea stars without this genetic resilience, but the sea stars that survived produced new, hardier sea stars. It's a wonderful example of nature adapting. In a time of rapid global change, it is heartening to see some things becoming more resilient as opposed to wasting away.
To this day it remains the most beautiful thing I have ever seen. While seen at greatest brilliance in the pitch black of a night with a new moon, there was a sliver of silver the evening I first saw Puerto Mosquito at night. Named for the insects that are prevalent alongs the banks of the small bay, this little body of water looks unassuming and muddy in the daylight. At night, however, when the water is moved by a boat, by a paddle, by your hand, or by fish and manta rays swimming beneath you, the water glows a brilliant emerald green, illuminating the darkness around you. In an instant you feel like somehow, when you weren't paying attention, you must have left Earth behind.
The glowing is due to a dinoflagellate called Pyrodinium bahamense. This is a tiny, one-celled creature that has two long, whiplike tales coming out of its body that flip around to move it through the water. This dinoflagellate has a unique beauty to it. When P. bahamense are disturbed, they glow, a process called bioluminescence. It's only for a fraction of a second, but when there are many of them, their agitated glow is profoundly beautiful. While these small cells are many places, few places are they as dense in the water as Vieques, Puerto Rico, where their vast numbers fuel both the local economy and the excitement of those lucky enough to make it to Vieques. Not only is this bioluminescent bay beautiful, but it is one of the brightest and most pristine in the world. You can see it for yourself in the video below.
Yet the balance of this bay is delicate. These plankton need a very particular environment to live in. If the water changes in the slightest, if it gets polluted, if the trees lining the bay disappear, or even if the wind changes, the system can be thrown. The magic could stop, and the bay might go dark. It has before.
On the last night I was in Vieques, the bay stopped glowing. It remained dark for months, worrying locals who rely on the bay for their livelihood and those who have already fallen in love with its eerie glow. The sudden darkness was a mystery, one that still isn't fully understood. Ultimately Puerto Mosquito began to glow again, but when Hurricane Maria hit, the brightness of the bay was hit once again, leaving the glowing water merely flickering. Once again it has made a slow recovery, and the glow has begun to return. These events though, paired with the permanent blackouts of other bioluminescent bays, only highlight how important it is to understand these delicate systems. If the bay is to continue to glow, the people of Vieques must understand what is going on.
Me at work on the bay in January 2014
The Vieques Conservation and Historic Trust (VCHT) is a local non-profit organization dedicated to the bay and to the surrounding community. It is the one that took me, a shy college student who had never been anywhere, and helped instill in me a passion for the natural world. They lead community meetings, monitor the bay, teach local children about the beauties of the island around them, and have helped rebuild this tiny island after Hurricane Maria. The people there are warm, hardworking, inviting, and passionate. They care deeply about the island around them and also about showing others the wonders of their small community. They have worked hard to rebuild after Maria, but while physical structures can be refortified, labs and equipment are harder.
Months after Maria hit, they still don't have a fully functional lab to continue the important work they do every day, monitoring Puerto Mosquito. They are trying to get it back up and running, but they need our help. If you make a donation (make sure to comment that is is for the lab), you are helping the people of Vieques to understand how best to protect the heart of their community. On an island where there is little industry and the economy revolves around tourism, protecting the bay is not only a scientific priority but a community priority. While the world can feel like it is spinning out of control, this is one small, concrete step you can take that will have an impact on the people in Vieques. And sometimes it's nice to protect some of the world's magic.
No brain, delicate enough to be killed by a bubble, bad swimmers, and... taking over the ocean? Jellyfish, on the surface, may seem like an unlikely set of creatures to be concerned about. Yet in recent years, jellyfish have become a huge problem in certain parts of the world, clogging fishing nets, shutting down power plants, and stinging vacations swimmers. While there isn't solid proof that the number of jellyfish is increasing globally, there has been a dramatic increase in specific regions, leading to concern that the future of the oceans may be gelatinous.
Jellyfish fall into two separate groups: cnidarians and ctenophores. Both groups have bodies that are gelatinous, are generally poor swimmers, and filter feed. The largest difference between the two groups is that cnidarians have long tentacles with stinging cells. These are the ones you want to avoid when swimming. Ctenophores, also known as comb jellies, are harmless and can't sting.
But why are animals that can't swim and that have such delicate bodies doing so well when so many species seem to be struggling? It's because jellyfish are what we call generalists, organisms that can live in a variety of places and eat a variety of food sources. Jellyfish do well when other species have trouble. Many species need just the right combination of temperature, oxygen, light, and even salt in the water, but jellyfish are resilient to these changes. We are also giving jellyfish a leg up. Humans frequently fish for species that eat baby jellyfish, meaning more baby jellies survive. Finally, with seawater getting warmer, jellyfish reproduce faster. In general, when humans throw a coastal ecosystem out of whack, jellyfish are the ones to remain, and not just remain but thrive.
These jellyfish can be a menace of the seas for a number of reasons:
They cause emergency shut downs in power plants, even nuclear ones. A lot of these power plants take in seawater to cool off the machinery. When the water is too full of jellyfish, it clogs up the entire plant, putting it in danger of overheating and making it necessary to close the plant until the jellyfish can be removed.. This can cause power outages in the region and ultimately costs a lot of money.
Jellyfish wreak havoc on fishers. They clog up the nets, sometimes so densely that the nets will break, and even sank a 10-ton fishing trawler in Japan. Jellyfish also eat baby fish, meaning that once there is a huge bloom of jellies, fewer fish make it to adulthood. Even if the nets of the fishers weren't entirely clogged with jellyfish, at this point there would be fewer fish to catch.
Jellyfish can get in the way of tourism. Nobody wants to go swimming in waters where they are likely to get stung.
A large presence of jellyfish can actually suffocate other animals. Jellyfish need less oxygen in the water than most species of fish. However, when jellyfish die, especially en masse, their bodies are decomposed by bacteria, which use up the oxygen that is in the water. This leaves little for fish to breathe, making water inhospitable for animals besides jellyfish and bacteria.
Massive blooms of giant jellyfish used to be rare. According to Shin-Ichi Uye, in Japan, where blooms of giant jellyfish have brought global attention, there used to be a massive bloom of jellyfish every 40 years. In the early 2000s, however, a massive bloom happened in 2002, 2003, 2005, 2006, and 2007. This particular species of jellyfish, Nemopilema nomurai, is massive: they can grow to be 6 feet wide and weigh over 440 pounds each! The fishing industry struggled as a result. In 2005 alone, fishers filed 100,000 complaints about the jellyfish. What did they think the cause was? Japan blamed it on water running into the ocean from China, bringing nutrients used for farming into the water. This could cause algae blooms and low oxygen conditions that jellyfish thrive in while other species suffer. Luckily for Japan, there haven't been huge blooms of jellyfish in recent years, but the experience was enough to leave people nervous.
Japan isn't the only place to see an uptick in jellyfish blooms. There have been problems in the Black Sea, in the Mediterranean Sea, and in many east Asian waters. Most of the places that have the most trouble with jellyfish blooms are the ones where there is the most human impact, meaning humans fish more there, there is more nutrients in the water from farming, there is more construction, and there are more non-native species that are brought to these waters, often the offending jellyfish themselves. But are jellyfish increasing globally? If waters get warmer, have less oxygen, and become more acidic, all things that we see happening, doesn't that set the stage for an ocean dominated by jellyfish?
Maybe. The problem is that jellyfish populations tend to fluctuate over the span of many decades. If the number of jellyfish fluctuate in a pattern every 40 or 50 years, you need a record of jellyfish that is at least 40 or 50 years long to say anything definitively, and in most cases we just don't have that. But with all the changes we see happening to the ocean, it is entirely possible that we will see more frequent, larger blooms in many areas.
So what can we do besides reduce pollution and do what we can to slow climate change? The answer may sound familiar; it is often a proposed solution when an animal takes over an ecosystem. We could eat them. In fact, in order to tackle a troublesome surplus of jellyfish in the Mediterranean Sea, there has been an effort to get Europeans to eat jellyfish. Chinese and Japanese cultures already embrace eating jellyfish. If life gives you lemons, make lemonade; if the ocean gives you jellyfish, make jellyfish burgers.
There are a number of animals in the ocean that can flash colors right before your very eyes. When threatened, a common cuttlefish may get a black stripe, like a masked bandit, over its eyes as its tentacles flair angrily. An octopus will change its color and texture to match its surroundings, making it practically invisible in the landscape.
How do these animals know when to change color? Are they expertly taking in their surroundings with their eyes, or is there something else at work? In an effort to get to the bottom of this phenomenon, researchers Schweikert, Fitak, and Johnsen from Duke University in Durham, North Carolina have decided to take a look at another one of nature's magicians, the hogfish.
Hogfish are brilliantly colored reef fish famous for their mating behaviors. All hogfish are born female, but after a female matures and reaches a certain level of social dominance, the female changes her sex and becomes a male. While hogfish live in groups, there is only one male, guarding his own personal harem. If something should happen to him, a dominant female will rise up, change sexes, and replace him.
Hogfish are just as adept at changing their color as they are at changing their sex, shown below in a video uploaded by Mark Karl in 2014.
The key to these changes lie in pigmented skin cells called chromatophores. Chromatophores rapidly rearranged pigments in the skin to change the color, morphing the appearance of either a small area on the animal or even the entire animal itself. However, scientists are still trying to figure out what tells chromatophores to change color. Rather than the hogfish seeing with their eyes, researchers believe hogfish are, in a sense, seeing with their skin, a process called dermal photoreception.
To test out this theory, the researchers at Duke University looked at the genes hogfish have in both their skin and in their eyes. Examining genes is one of the best ways to look at what is happening throughout the body because they serve as the blueprint for proteins in the cells. Proteins are essentially the workers of each cell, so by looking at genes, the researchers were looking at the job descriptions of proteins in the eyes and skin of hogfish. After these proteins do their job, however, the rest of the workers in the cell need to know what to do. Messages can be spread through the cell by other proteins in a signal pathway, a phenomenon similar to a game of telephone. Scientists can also see the code for this kind of communication in the genes. Essentially, the scientist looked at the job description of various workers in each cell as well as how these workers communicate to describe what was going on.
What the researchers found is that hogfish can see with their skin, although not in the same way they can see with their eyes. Hogfish have a protein in their skin called SWS1 that can sense ultraviolet light; in contrast, hogfish eyes have five separate proteins that can be used to see. In addition, the signal pathway that SWS1 uses to communicate, called cAMP, is different from the signal pathway used by the proteins in the eyes, or cGMP. This means that while hogfish use both their eyes and their skin to see, the eyes and the skin don't have the same proteins, and these proteins don't communicate in the same way. While both the eyes and the skin of hogfish can be used to sense the light around them, both parts of the body are doing it in a completely different way.
This discovery is groundbreaking; it is the first time that scientists have been able to show that color-changing fish can sense visual signal, light, with something other than their eyes. There is a lot more work to be done to figure out how much the color of the fish is impacted by the eyes versus the skin and how this factors into how other animals change color. Still, this is an exciting first step in exploring one of nature's coolest phenomenon.
Article Citation:
Lorian E. Schweikert, Robert R. Fitak, Sönke Johnsen. De novo transcriptomics reveal distinct phototransduction signaling components in the retina and skin of a color-changing vertebrate, the hogfish (Lachnolaimus maximus).Journal of Comparative Physiology A, 2018; DOI:10.1007/s00359-018-1254-4
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