Apple #645: Where do Fish Go in Winter and in Drought?

The park where I like to go walking has a little walking bridge that goes over a stream.  I like to pause there and look into the stream because after a while, I usually see a few small fish in the water.  I find it a hopeful sight.  So much so that I usually wait until a fish or two swims into view.



The fish I see in this particular stream are rather small and non-descript, kind of like this lady here, who is a chub.
(Photo from Rugbymadad's Blog)


But lately, I haven't been seeing any fish in that stream.  There were some rainstorms that changed the configuration of the shallows and deep spots, so I thought maybe the fish had moved to some other location in the stream.  But it's also been quite dry lately.  In fact, much of the stream these days seems so shallow, I wonder if it's even enough water for those fish.

All of which made me wonder, when the water gets shallow, where do the fish go?  Do they hide in the mud until the water comes back?  And for that matter, where do the fish go during the winter when the water that is their habitat freezes over?

It turns out, what fish do during dry weather and what they do during winter are very similar.  Let's start with the winter situation first.

Winter Cold & Ice

• As a river or a pond freezes, the ice forms at the surface first.  As the weather gets colder, the ice gets thicker from the top down.  The warmer water is at the bottom or deepest parts.  So the first line of defense against ice is for the fish to go to the deepest waters.

• If you're ever able to see through the ice to spot fish in the water, you'll probably notice that they're grouped together.  You might be tempted to think they're huddling together for warmth, but since they're cold-blooded creatures, that concept doesn't really apply to them.  They're close-packed like that because that deep, warmer spot isn't that big and they're all trying to fit themselves in that little space.

Koi just below the surface of the ice. Since they're hanging out together, I'd guess they've found a warm spot.
(Photo from Silver Pines Lodge. This page tries to launch an application that you're probably better of refusing to allow.)

• So now you've got a cluster of fish packed into a small space.  Kind of like a lot of people stuck in a small closet--after a while, you'll notice that everybody's been breathing up the oxygen.  The same thing happens to fish under the ice.

• Not only are they packed together in those deeper pockets, but the ice at the surface is also cutting off the supply of fresh oxygen to the water.  There are also fewer water plants doing their photosynthesis thing, so there's less oxygen coming from the plant source, too.  

• Because fish are cold-blooded, their body temperature drops when the water temperature drops, and they become less active.  So they don't need as much oxygen in the winter as they do in the summer.  

More koi under ice.
(Photo from Koi Fish Care)

• However, if the ice gets too thick or too expansive, the oxygen level can drop to a point that is problematic enough that the fish have to find other solutions to the problem of winter.

• Some fish migrate.  They go to warmer waters, or deeper waters, or they go to places where the water is more turbulent -- near rapids or other incoming streams or springs, or even near waterfalls.  The churning water keeps ice from forming and also allows the water to be replenished with oxygen.

• Other types of fish enter a state called torpor, or diapause.  It isn't true hibernation because they can be roused, but the concept is similar.  Everything drops to a state of very low activity -- respiration, heart rate, digestion, growth -- pretty much everything slows way down or even stops.  This further reduces the amount of oxygen they need to survive and helps them get through the iciest, lowest-oxygen part of winter.

• Some fish, like carp, do bury themselves in the mud, as well as going into diapause.

• Still, in spite of their efforts, fish sometimes just can't hold out in such oxygen-deprived icy waters, and they die.  When lots of fish die in the winter, it's called winterkill. It can take 3 to 4 years for a fish population to recover from a severe winterkill.

A school of fish struggling to get to the oxygen bubbles in the ice in a pond in St. Petersburg.
(Photo from AtBreak)

• Don't be too alarmed, though.  Some amount of winterkill is par for the course.  As one fish expert says, "In some waters, partial winterkill is just a natural and beneficial process that results in faster growth rates for the survivors."

• Even though some fish have to take lots of measures to survive winter's cold and ice, other fish are so well-adapted to cooling temperatures that their big feeding time is the beginning of winter.  Lake trout, brown trout, whitefish, and panfish take advantage of the fact that their summertime competitors have moved to deeper waters, or they have less vegetation to hide in, or they have slowed down so much that they become prey.  Put simply, these cool-friendly fish dig winter.

• Here's one last thing about what can happen to fish during winter: they can get "drunk" on oxygen. After the first ice has formed on a body of water but before enough snow has fallen to block the sunlight, the plants growing in the water are still using that sunlight to photosynthesize and produce more oxygen.  The ice traps that extra oxygen so the water becomes saturated with it.  So some fisherman occasionally see fish just below the clear ice, swimming sort of goofily on their sides, as if they're drunk.  In fact, they've imbibed too much oxygen. 

 
These fish are hiding out under a dock in Long Lake, MN.  It's a whole different world under the water, one that fish know very well.
(Photo from Fargo-Moorhead Dive News)

Summer Heat & Drought

• In the summer, fish are not so much bothered by the heat directly as they are by the heat's effects, which is to say the heat causes the water to evaporate, which means less water in which to swim and breathe. That's a much bigger deal for fish than air temperature.

• Well, warmer air temperature eventually becomes warmer water temperature, and the fish that like the cold waters don't do well when the water gets warm.  Some coldwater fish such as brook trout can become stressed from warming waters.  They may not grow very large, or they may not reproduce in their usual numbers, or they may die.

• Warmer temperatures do mean less oxygen, and the reduction in oxygen is the real problem for fish.  But just as fish seek out deeper waters in the winter, they also seek out deeper waters in the summer.  Where the deep water was warm in the winter, in the summer, the deep water stays cooler.  So the fish will move to deeper, cooler waters if they need to when the temperature rises.

• These deeper, cooler waters may be little pools within a stream, or waterholes lining a streambed, or eddies along a riverbank.

Rivers have all sorts of geographies to them.  The fish know the lay of the land and where to go when it's too warm, or too cold.  Fisherpeople study diagrams like these so they know where to go to catch the fish.
(Diagram from Wikibooks)

• Again, a few species of fish bury themselves in the mud and wait for the waters to come back.  The mud-minnow is uniquely adapted to low-water situations.  It can either extract oxygen from water through its gills as all other fish do, or it can also get oxygen from the air.  

Mud minnows or mudfish are really common, and lots of fisherpeople use them to catch other, larger fish. But perhaps the reason they're so common is they're able to cope with adverse conditions of all sorts, and produce plentiful offspring.
(Photo by blackmagic on 2CoolFishing)
 

• But when the air temperature climbs so high that the water doesn't just get warm but starts evaporating (or if a dam has been constructed that blocks the flow of water), then the fish have a real problem.  Not only do the oxygen levels drop, but the shallow areas turn completely dry, so rivers and streams that used to be connected to each other can get broken up by dry patches (or made impassible by dams).  

• Thus the fish may not be able to get to important places like bountiful feeding grounds, or they may not be able to reach the place where they go to spawn. Or sometimes fish lay the eggs in one place, counting on the current to carry the eggs to another place where food for the young is plentiful.  But with the river broken up, the eggs can't get there.  The eggs hatch in a less friendly environment and the young starve or get eaten.

• Also during a drought, the vegetation that some species of fish use for hiding may recede, which means the fish are more exposed and thus more vulnerable to their predators, a.k.a. they get eaten.  

• Conversely the vegetation underwater can grow so thick on a glut of sunshine that sunlight eventually can't penetrate deep enough to reach them anymore.  Throw in a few warm, still, and cloudy days, and you've got no sunlight reaching those water plants at all.  They can't do their photosynthesis thing, which means they're producing less oxygen.  With no wind or motion in the water to stir things up and aerate the place, the oxygen levels drop, and pretty soon the fish are gasping for breath.  If that situation continues for too long, the fish will die.

This is what you want a riverbank to look like, if you're a fish. Some vegetation that reaches into the water and provides cover and oxygen, but not too much. Also enough wind and current to make ripples and keep the water nicely aerated.  This is in Devon, England.
(Photo from Barry's Musings and Family News)

• In fact, if any of these low-water situations continues long enough or is pervasive enough, the fish will die.  Just as winterkills can happen, so do summerkills.  A partial summerkill is not uncommon.  But widespread, large-scale summerkills are more of a concern.  

• Places in Nevada in recent years have seen summerkills as high as 20,000 fish.  Recent droughts in the Plains states have resulted in the die-off of enough fish that some native species of fish such as the silver chub have all but completed disappeared.

What You Can Do

• People who have ponds stocked with fish can do a lot to prevent winterkills or summerkills by aerating their ponds.  That means basically stick a fountain in the middle of it and keep it running summer and winter. 

• Or if you don't have a fountain and you see fish acting sluggish at the surface of the water and visibly gulping at the air, that's the equivalent of the fish calling 911.  You can aerate the water yourself by using a 2- to 3-inch pump, like a pump you might carry on a bicycle, and pumping and spraying water back into the pond.  That's not an ideal solution because the aeration needs to continue until the oxygen levels are restored, and that usually takes at least over night.

• There are a ton of websites that say their aerators are the best.  For some background information on types of aerators and how aerator performance is measured, check out the Southern Regional Aquaculture Center's information sheet on Pond Aeration.

There are lots of different types of aerators that make the fish happy. This one happens to be a floating fountain.
(Photo from Qrbiz.com)

• You could also do what we used to do when we were kids, which is dig little trenches to connect one body of water to another.  We were just playing in the creek when we did that, but it turns out that's pretty important.

[Edit:] In the days since I put this post together, it's occurred to me that when I go swimming in a lake, splashing and kicking around, I'm actually doing the fish a favor.  All that splashing is aerating the water. That's nice to think about.


You might also be interested in: Where Birds Go When it Rains; Rivers

Sources
Alisa Santiesteban, Wisconsin DNR, A cold world with an icy ceiling, December 2009
Minnesota DNR, Fish in Winter, 2010
The Ohio State University School of Natural Resources, Winter and Summer Fish Kills in Ponds
eWater Australia, Where do fish go in a drought?
Environment Agency UK, How does drought affect fish? April 2012
Full Service Aquatics, What Happens to Pond Fish in Winter? January 25, 2011
Rob Neumann, Department of Natural Resources Management and Engineering, University of Connecticut, Impacts of Drought on Fish
Drought, heat lower reservoirs, impact boating, fish in Northern Nevada, Reno Gazette-Journal, June 24, 2013
Drought, River Fragmentation Forcing Endangered Fish out of Water, Biologist Finds, Science Daily, June 6, 2013

Apple #573: Venus' Flower Basket

I just got back from a good but tiring vacation. I must get some sleep, but before I do, I want to find out about something I encountered on my vacation -- a Venus' Flower Basket.

I was in a natural history museum when I saw the skeleton of this thing. The note next to it said that the skeleton is made of silica -- glass. My jaw dropped. A living creature's skeleton is made of glass? I must know more.



The bleached skeleton of a Venus' flower basket, or a glass sponge. The fibers are made of silica, a.k.a. glass.
(Photo from the Natural History Museum, London)

• This animal -- yes, it's an animal -- is a type of sponge.

• Venus' flower baskets (Euplectella or Eupectella aspergillum) live in the ocean where the water has lots of silica and is very cold, which often also means that it's very deep, anywhere from 10 to 5,000 meters below the surface.

• They live mainly in the South Pacific off the coast of Japan and the Philippines, but they've also recently been found off the coast of Australia.

• When they're alive, the sponges can range in color from white to creamy yellow. The "skeletons" that are often displayed in museums are typically the tissue of the sponge which has been dried and bleached to give it an even whiter color.

Three Euplectella living underwater. They don't live in colonies the way coral do; it's just that these three happened to set down roots near each other.
(Photo from telecomBlog)

• Their shape is what allows these sponges to survive in the huge pressures that exist at such ocean depths. How they make their shape has been the subject of a lot of research.
  

• Like all sponges, Venus' flower baskets are filter feeders. One of the things they filter from the water is silica.

• The sponge has special cells called spicules. The spicules extract silica from the seawater, and then they set the silica bits on top of a wire of collagen protein. So the structure gets built bit by bit, but very delicately. This process is known as biomineralization.

Looking down into the internal cavity of a Venus' flower basket
(Photo from Tecnologia e Desenvolvimento Sustentavel)

• Lots of sponges do this biomineralization thing. What's unique to the Venus' flower basket is the way in which it builds its layers of silica.
  

• The spicules themselves have three perpendicular rays, which gives them 6 points. As the sponge biomineralizes, it forms more spicules. It lays them down, layer by layer, each a few millimeters thick. Between each layer is a thin layer of "organic matrix" that functions like glue. There are seven different types of layers, each arranged concentrically and hierarchically.
  

• Outside the mesh of spicules is another set of cells. Some people call these filaments, some call it a trabecular net, others call it a synctium, still others call it a cobweb. Whatever you call it, these form an outer layer and they get wrapped around the mesh in various orientations: horizontally, vertically, and diagonally.
  

• This outer layer helps to make the structure a little more sturdy, which is very important since glass is very brittle, and this animal's entirely-glass skeleton has to survive at very pressure-heavy depths.

This image gives you a good sense of the underlying mesh and the syncytium that winds around the top of it.
(Photo from Richard L. Howey's page on the Euplectella aspergillum)

• "As yet," says one researcher, "it is not clear how a primitive organism can produce such a complex and optimized structure at all."

• But wait, there's more.

• Inside the mesh is an open cavity where the ocean waters wash through and get filtered. One of the things that floats into the cavity are tiny shrimp larvae.
  

• The shrimp larvae stay in there, eating happily away until one fateful day when they discover they've gotten too big to swim back out again. Sometimes a few get trapped in there, but often it will be a pair, male and female.
  

• So people have made up a quaint little story that the shrimp have found each other and live out their wedded bliss together until death do they part within the chambers of the sponge.

• This is why the sponge is named after Venus, the goddess of love.

• This is also why the Japanese often give each other these sponges (after they've been collected and dried) as tokens of love or as wedding gifts.

• What I find even more fascinating than that sentimental gush is the fact that a sponge which is entirely made of glass can not only survive super-high pressures of 1,000 meter ocean depths, but it can also survive little pincer bites from the pair of shrimp who take up residence inside its body. Tough little cusses, these underwater glass nets.

• And in real life, the shrimp and sponge live symbiotically. The shrimp clean the interior walls of their sponge-cage with their little pincers, and in return, the shrimp get to eat some of the food the sponge takes in.

Shrimp inside a Venus' love basket. Is it eternal love between shrimp, or is it really intraspecies cooperation -- which may itself be a form of love?
(Photo from Fresh Photons)

• Oh, did you think that was all these things can do? No no, my friends. There's still more.

• OK, so the sponge's eggs mature inside the females and get fertilized there, and when they become larvae, they get spewed out of the sponge. Released into the wide ocean, the larvae beat their little ciliae to propel themselves through the water, looking for their new home.
  

• These little freddies can swim for several days, but most tend to find their favorite spot on the ocean floor after about 12 hours. Once they've landed, a tuft of fibers at the end of the animal attaches to the ocean floor, and then they begin developing into adults.

• Here's the jaw-dropping part. That tuft of fibers is not just a mass of weird-looking hairs. The fibers are very fine and very long, sometimes up to 175 meters. Because they're so fine and they're made of silica, their composition happens to be a lot like fiber-optic cables. Exactly the same, in fact. Which means that these funny little hairs sticking out from the end of this animal can trap and transmit light.

Most of the bleached skeletons have lost the little fibers at the end, but here they're intact and very visible. This sponge has tons of those little hairs. Which can act like a fiber optic cable.
(Photo by Ryan Somma, sourced from oneworldoneocean.org)

• Wait, did I say they're exactly the same as our fiber optics? I was wrong. They actually work better than the fiber optic cables we make. And the animals are more efficient at making their fiber optics than we are.
  

• No one is sure if the sponges use their fibers' ability to transmit light for a particular purpose and if so, what that purpose might be. Some researchers speculate that those fibers are how the animal attracts one of its favorite foods, which is algae.
  

• Or perhaps the light is what attracts those shrimp larvae, which are bioluminescent. This theory is that the shrimp see the light from the little hairs and, thinking it's more shrimp, swim inside. Thus the sponge gains its symbiotic partners.
  

• Oh, and by the way, what with those bioluminescent shrimp in there and the fiber optic hairs floating off the bottom, these creatures glow in the super-dark that is the very deep depths where they live.

Like all sponges, these animals have no brain, no nervous system at all, no organs like a heart or stomach or kidney. They don't even have that many types of cells. Yet they build their own bodies in these complex, mathematical shapes, they make their own fiber optic cables, they glow in the dark, and they house a pair of shrimp for life to boot. Pretty incredible stuff.


Sources
Natural History Museum of London, Eupectella aspergillum (Venus' flower basket)
Encyclopedia Britannica, Venus's flower basket
Max Planck Research, Secrets of the Venus' Flower Basket, April 2005
Queensland Museum, Animals of Queensland, Unique features of sponges, Organic & inorganic skeletons
University of Michigan Museum of Zoology, Euplectella aspergillum
Una esponja submarina genera fibras ópticas mejores que las industriales, telecomBLOG
Peter Weiss, Channeling light in the deep sea, Science News Online

Apple #486: Jellyfish

I went to a nearby aquarium with some friends this summer.  I meant to do a Daily Apple entry about some of the fish & animals & creatures I saw there, but I've only just now remembered.  So I give you: jellyfish.


I don't know what kind of jellyfish this is because the aquarium decided to get all entertainment-y, and they took all the "boring" stuff off their signs, such as the names for the animals.  But I do know this is some kind of jellyfish.  It was in a tank with curved glass on the outside and it was lit up with that bright pink light so the jellyfish would be visible.
(Photo by the Apple Lady)


Some Nice, Easy Facts

• Jellyfish have existed for more than 650 million years.  That makes them older than dinosaurs, older than sharks.

• Individually, each jellyfish lives for about three to six months.

• Jellyfish never stop growing. However, since they don't live very long, "never" for most jellyfish is a short time.

This jellyfish was in a different tank than the pink one. I don't know what species it is, but it's a different one than in the first picture.
(Photo by the Apple Lady)

• A group of jellyfish swimming together is called a smack.

This is a whole bunch of jellyfish.  A smack of them, I should say.  The colors didn't come out too well in the photo, but the frondy things -- which I guess must be tentacles -- are green on some of them, pale purple on others, and pale pink on still others.
(Photo by the Apple Lady)

• Female jellyfish store their fertilized eggs in their "oral armpit," which is actually more mouth than armpit.

• One fertilized egg turns into a polyp, which is sort of like a  seed pod.  The polyp generates more polyps off of itself.  The polyps  break open and inside of each one are several tiny jellyfish.

 
Jellyfish #3
(Photo by the Apple Lady)

• Jellyfish are pretty simple, anatomically speaking. They do not have:

• brain
• central nervous system
• circulatory system
• respiratory system
• bones
• scales
• shells

•  Jellyfish do have:
• epidermis (skin)
• gastrodermis (skin around the digestive system)
• mesoglea (fancy word for the jelly-like goo)
• rudimentary digestive system
• nematocysts (stinging cells)

• Not all types of jellyfish have tentacles. The stinging cells might be on other surfaces of their bodies.

Ah, don't these jellyfish look nice and peaceful, almost as if they're dancing?
(Photo by the Apple Lady)


The Rest of the Story

You might be tempted to think that jellyfish are pretty and colorful and nice and simple.  But jellyfish are actually much more complex and capable than you might think.  In fact, it's possible that they could be taking over the world.  Or at least, the oceans.

• Because of overfishing, jellyfish are able to reproduce pretty  much at will and with far fewer predators.  As a result many of our  oceans are approaching what scientists call a "jellyfish stable state,"  which will be when jellyfish effectively rule the ocean.

• Echizen jellyfish, for example, are growing like mad off the coast of  Japan probably because of overfishing. This species can get to be over 7 feet in diameter and weigh more than  660 pounds. 

This is the Echizen or Nomura's jellyfish, which live off the coast of Japan. Pretty dang huge.
(Photo from Beer Steak)

• Another species of jellyfish can avoid death.  Not by dodging predators or anything so basic as that.  They can make their cells literally get younger.

• The fancy name for this process is transdifferentiation, and only the Turritopsis Nutricula jellyfish can do it.  In transdifferentiation, as a cell develops, it gets younger instead of older.  So basically this jellyfish, when it's had enough of aging, can make itself revert to a polyp state and essentially rebirth itself.

• As far as scientists know, these jellyfish can do this over and over again, indefinitely.

• Another type of jellyfish, the sea wasp or box jellyfish, kills more  people per year than any other creature in the ocean.  Including sharks.

• That box jellyfish, by the way, has 24 eyes and 64 anuses. And 64 mouths as well; jellyfish use the same orifice for eating food and expelling  wastes.

Here are a couple of pictures to show you what a box jellyfish looks like. Its cap -- for lack of a better word for it -- has a dome-like top and it comes down quite a ways over the tentacles. If you see one of these, get the heck away from it fast!
(Photos from Destination-Scuba and Scubadoc, respectively)

• What makes any jellyfish's sting so virulent is, to quote a scientist from a National Geographic video, "all the blood cells that are exposed to a jellyfish's venom will immediately swell up and explode." 

If You Get Stung

• If you've been stung by a box jellyfish, you've got 3 minutes to get the venom off you before you die.

• Other types of jellyfish, it's not so dire, though it can be extremely painful.

Jellyfish sting
(Photo from Bryanking.net)


Box jellyfish sting
(Photo from Scuba-doc)

• If you're having trouble breathing or swallowing, or if you're having chest pain, get thee to a doctor immediately.

• Best thing to do is--no, not urinate on it--is first, get any stuck-on tentacles off of you.  Don't use your bare hands but use tweezers, a gloved hand, a stick--anything to peel off those  tentacles.

• Then as soon as possible, rinse the area with any one of the following liquids.  In order of preference, most to least effective:

• Vinegar
• Rubbing alcohol
• Either of the first two diluted with salt water
• Salt water

• Fresh water, ice, or hot water can make the nematocysts (stinging cells) release more toxins, so you definitely want to avoid using those.

• If you've gotten stung around the eye, then use a ton of fresh water -- a gallon of it -- so as to overwhelm the nematocysts with a liquid that won't sting the crap out of your eye still further.

• Even after you've plucked off the stingers you can see and after you've rinsed, you still probably haven't gotten all the stinging cells off of you, so apply shaving cream or baking soda or cornstarch or mud or sand to neutralize the stinging still further.  Then shave.  If you don't have a razor handy, use something like a credit card or a hotel key to scrape the area as best you can. 

• Then rinse again with vinegar or alcohol.

• Finally, wrap the area in an Ace bandage the same way you'd wrap a sprain, and take some aspirin.

• After you've rinsed and bandaged yourself, you might want to go see a doctor anyway.  The doctor can give you Benadryl to calm any itching, steroids to reduce any inflammation, and pain medication if necessary.  It's also easy for jellyfish stings to get infected days later, so you may need antibiotics too.

• A final word about the urine thing: some people say it helps reduce the sting. But it's a gamble. The thing in urine that works to neutralize the nematocysts is ammonia. But most people's urine has a far greater amount of fresh water than ammonia.  So urinating on a jellyfish sting can actually increase the pain, the same as pouring fresh water on it would.

• You're not Joey and Chandler and Monica and you're not on TV.  Use vinegar.

Some places in Australia where box jellyfish are particularly prevalent have gigantic hydrants like this one filled with vinegar.  This is because vinegar is the best thing to use to rinse off jellyfish stings.
(Photo from Life in the Fastlane)


Sources
Aquatic Community, Jellyfish Facts
Roy D'Silva, Buzzle.com, Facts About Jellyfish
Beer Steak, Jellyfish Facts

Scienceray, Weird But True: Jellyfish Facts
Simon Crisp, Asylum for All Mankind, Giant Echizen Jellyfish Invade Japanese Waters
Rod Brouhard, About.com, How to Treat a Jellyfish Sting
emedicinehealth.com, Jellyfish Stings Treatment
WebMD, Jellyfish Sting Treatment

Apple #482: Sharks

I've been sick this week.  No energy for much else besides sleeping and lying on the couch.

So now, for no particular reason, I give you sharks.


The Great White Shark, or more simply, the white shark. Here's what Jacques-Yves Cousteau reported when he encountered one: "Shark saw us, its reaction was unexpected. Frightened, it released a cloud of excreta and disappeared with incredible speed." Basically, the shark crapped its pants at the sight of a human and ran.
(Photo from Daily Scuba Diving)


SHARK ATTACKS
or You've Got More Fish to Fry Closer to Home

Movies like Jaws -- which I will stop and watch any time it's on TV, by the way. "Smile, you son of a" -- and cable TV shows like When Sharks Attack! have inflated people's fears of sharks.  In real life, most of us have very little reason to fear sharks compared to all the other life-threatening things out there.  Here are some facts to put sharks in perspective:

(If you want the details, click the Read More link)

Apple #377: Octopi

Recently, I saw a news story about an octopus in aquarium that escaped from her tank. I'm not exactly sure how she did it, but she also managed to open some sort of valve that allowed salt water to gush out onto the floor of the aquarium -- 200 gallons of it. She survived the flood, as did all the other animals in the aquarium. After the staff closed up the place in her tank where she busted out, she "sits in her tank as if nothing happened."

This reminded me of a YouTube video a friend of mine told me about a while back where you can watch an octopus do all sorts of things -- including opening a jar to get a a crab inside, finding its way into an Erlenmeyer flask also to get at its lunch, and squeezing itself through a narrow tube. Watching this video was pretty much how I learned just how wily octopi can be.

Here's the video he told me about. And no, I don't know what's up with the music.

That video is edited so you can't really see how the octopus removes the jar lid. In this one, you can see the entire process from start to finish. I think the noises in the background are the TV and the octopus owner's bird.

• Scientists don't know that much about octopi because they're very good at avoiding humans, and they tend to hide when divers come around to look at them.

• Another reason it's hard to study them, says one biologist at UC Berkeley, "If you watch them, they watch you back."

• Octopuses are cephalopods (squids, octopuses, cuttlefish, and nautiluses). The word cephalopod comes from a Greek phrase which means "head-footed." Their bodies are really a squishy head which is called the mantle, a bunch of arms, and a foot. The foot is the thing they grasp with and it is attached to the head, hence the name.
  

• Scientists think that cephalopods have been around for 500 million years.

• All cephalopods have three hearts. Two of the hearts pump blood to the gills and one pumps blood to the rest of the body.

• Another feature of cephalopods is that they have eyes that look a lot like human eyes, and they are "vision-forming," which means they aren't just spots designed to look like eyes and fool possible predators, but they actually work and help the cephalopods to identify and track the food they're about to eat.

• The ink that most cephalopods expel to confuse any attackers is made of melanin, the same stuff that pigments your skin.

• Cephalopods have large brains and some species are known to be able to learn and retain information. I'm willing to bet that, since we don't know all that much about them yet, scientists will find out that even more species of cephalopods can learn, and that they're all a lot smarter than people realized.
  

• All cephalopods are nocturnal.

The Coconut Octopus in Sulawesi. Impressive creature, isn't it?
(Photo by Alistair Watters)

• As you probably learned in elementary school, octopuses have eight arms.
  

• Octopuses mostly eat crustaceans like crabs, shrimp, lobster. They'll also eat clams or fish, and they may also eat other octopuses.

• The Smithsonian and other zoos are trying to learn more about octopus behavior and capabilities by putting stuff into the tank with their octopus -- things like jars with lids, laundry baskets, shelves, doorways, rubber dog toys, etc. -- and seeing what the octopus does with them. Octopuses will inspect these items, climb on them, or if they're small enough, move them around in the water with jets of air -- effectively playing with them.

• One researcher put a bunch of stuff like plastic jugs, plates heaped with pebbles, and clumps of algae in the bottom of an octopus tank, making a maze that hid the exit. She tried this out on a few different octopuses, and it only took a few tries before they found not just the exit, but the quickest way to get there.
  

• She even moved them from one maze to a second one and back again, and they were apparently able to remember what they'd learned the first time they'd been in the maze.

• Octopuses are also very skilled at camouflage. They can suddenly change their skin color to match the color of coral or nearby plants, or they can turn themselves completely white to scare off a predator. It's not an octopus, it's a ghost octopus!

The Blue-ringed Octopus is venomous. It turns its rings bright blue to warn predators. If they get too close, this octopus can bite and inject the neurotoxin into the wound through its saliva. The venom is so potent, it can cause heart and respiratory failure in a human being within minutes.
(Photo by Roy Caldwell, California Academy of Sciences)

Here are some photos of the Blue-ringed octopus camouflaging itself.

• One particularly impressive trick is to make themselves look like a rock. But they don't just take on the coloring and shape of the rock. That wouldn't be that effective because they would have to sit completely still at the bottom of the ocean. No, the octopus dons all the appearance of the rock and then it moves very slowly across the ocean floor at the same rate of speed as the light moving in the water. So what looks like a rock with light playing over its surface of the rock is really an octopus in disguise sneaking up on some dumb crab.

• Octopus mating is about as complex and involved as the rest of octopus behavior. When a male octopus woos a female octopus, he can use all sorts of techniques to get her attention. Some male species of octopus have stripes that become visible only when the male turns them on, so to speak, so he might flash his stripes at her. He might also puff himself up or even link arms with her.

• Some sneakier males don't turn on their male stripe until they get really close to the female in her den. So they think the male is a female until he's right up next to her, and then he'll flash his male stripes not so much to get her attention but to keep other males from coming around.
  

• When the male and female are ready for it, they move off together away from the den, holding hands. Or arms. Or tentacles. Then the actual mating can take place several times over. The male has a special arm called the hectocotylus which he extends and slips into the female's mantle cavity, where his octopus sperm gets deposited.

Octopus mating. He is inserting his hectocotylus into her mantle.
(Photo by Roy Caldwell, UC Berkeley)

• After they're both satisfied, she goes back into her den and lays tens of thousands of eggs. The eggs are laid on strings which she weaves together into a kind of web and attaches to the ceiling of her den. She takes care of the eggs by blowing jets of water on them to keep them clean and warm.

• She can't leave the den to get food, though. So she starves to death while the eggs grow. After about a month or two, the eggs hatch and the mother dies.

• As for the father, usually he only lives a few months more after mating.

• Depending on the species, an octopus may live only a few months or for a few years.

UPDATE 12/o9: Scientists recently revealed video of veined octopuses who live on exposed, sandy sea floors, picking up discarded coconut shells, tucking them skirt-like under their bodies, and running with them across the ocean floor. Once they get to a suitable place, they plunk down, pull the shell over themselves, and lurk in their new, convenient hiding spot. Or, if they've been lucky enough to find two halves of a shell together, the close the shell around their body and hide in there.

This article from the BBC has the video.


Sources
Smithsonian National Zoological Park, Cephalopods, Giant Pacific Octopus Behavior Watch, and Zoo Exhibit
Tree of Life, Cephalopoda
Joey C's Study of Octopus Behavior, Stone Middle School, Melbourne, Florida
Carl Zimmer, How Smart Is the Octopus? Slate.com, June 23, 2008
Yasmin Anwar, "Octopus sex more sophisticated than arm-wrestling," UC Berkeley press release, March 31, 2008

Apple #340: Sea Fans

I just got this book out of the library called Chasing Science at Sea: Racing Hurricanes, Stalking Sharks, and Living Undersea with Ocean Experts. It's about what it's like to be an underwater researcher and what sorts of adventures and problems people have encountered while trying to learn more about sharks or anemones or other undersea things.

The same way my dad reads non-fiction books, I turned to the pictures first. I was hoping for full-color photos and these are only black and white, but still, there are several undersea photos. Mainly they're of various underwater research vehicles and the occasional shark.

But there's one photo of a particular kind of coral that I've always thought was really cool-looking. So I'm going to find out what it is, and then I want to learn about what it does.


Sea Fan, from the Grand Cayman Islands. Fantastic, isn't it?
Photo from Florent's Guide to the Tropical Reefs, which has tons of great color photos of fishes and coral.

• This thing is commonly called a Sea Fan. You've probably seen them in fancy fish tanks, maybe at a Chinese or Japanese restaurant, or maybe you've seen them at your local aquarium or zoo.

• Sea fans are part of a larger family of coral called Gorgonians, which includes sea whips, sea plumes, and sea rods as well as sea fans. It's sort of confusing figuring out what's a sea fan and what's not. Apparently the family classifications have been changed a few times and not everybody is on the same page as far as what belongs in which group.

• For our purposes, I'll show you pictures of things that are for sure Gorgonians and that are probably also sea fans, as opposed to those other types of Gorgonians. Even those Gorgonians that are considered to be sea fans can have lots of different shapes.

Various types of Red Gorgonians, some with polyps extended.
(Photo from a German site about marine zoology, with lots of photos, called Senckenbergische Naturforschende Gesellschaft)

• All Gorgonians are types of soft corals, which means they don't calcify and fuse themselves together to become almost like rock, but instead they anchor themselves in thick beds of sand or mud, and they have a flexible, bendy skeleton made of a specific type of protein called gorgonin. This protein is very similar to the collagen in our tendons, except it is twice as strong.

• To me, the fact that may be the strangest about these things is something that's true of all coral: they're not plants, they're animals.

• But what's confusing is that some sea fans are photosynthetic (require light to process their food) and some are non-photosynthetic. But only plants are photosynthetic, you say, so how can sea fans be animals and also be photosynthetic? Very good question.

• The reason some sea fans are photosynthetic is they have tiny little planties that live among them, called zooxanthellae. Those zooxanthellae are actually very tiny, single-celled algae. The Gorgonians provide the algae with a place to live that's close to the sunlight and and their waste matter also provides food for the algae. In exchange, the algae produce oxygen and nutrients that are essential for the Gorgonians to be able to grow and reproduce.

Close-up of a coral's polyps showing zooxanthellae. On this particular coral, they're the reddish-brown stuff that looks sort of like rust.
(Photo was originally from a Biology course page at U Michigan, but which has since been taken down. Sourced from Estrella Mountain Community College page on stem eukaryotes)

• So if you've got a photosynthetic Gorgonian, that means it needs the little algae planties on it to survive, which means you've got to give your Gorgonian sunlight. If you've got a non-photosynthetic Gorgonian, you have to make sure it can get its necessary food and nutrients for itself. People who have aquariums say the non-photosynthetic varieties are harder to keep alive. Most Gorgonians are non-photosynthetic and prefer shadier, deeper waters.
  

The Purple Frilly Gorgonian is a photosynthetic gorgonian and favorite with people who keep home aquariums.
(Photo from Quality Marine)

• By the way, most types of coral have a symbiotic relationship with the zooxanthellae. In fact, in most cases, it's the tiny algae growing all over the various types of coral that gives it its bright colors.

• Whether they are photosynthetic or not (rely on mini-algae or not), they all have polyps that are fringed with tentacles. The polyps are crucial to the way the sea fans eat and grow.

Yellow Finger gorgonian with polyps closed.
(Photo from Live Aquaria, where you can purchase a Yellow Finger for $29.99)


Yellow finger gorgonian, with polyps extended.
(Posted by Nano at saltwaterfish.com)


Close-up of a red gorgonian and its multitudinous polyps.
(Posted by Nano at saltwaterfish.com)

• At night, the sea fans extend their polyps, which have stinging tentacles on the ends of them. Any food (plankton, mostly) that floats close enough gets trapped or stung and paralyzed by the tentacles. The food is then passed to the center of the polyp, which is kind of like a mouth.

• This video shows a few different types of sea fans. There's no sound, and the first few sea fans aren't doing much, just waving slightly in the current. But then it zooms in on one that has its tentacles extended, and you can see them close around food like a fist. It is totally cool.

Viminella, another type of Gorgonian.
(Photo from the German site Senckenbergische Naturforschende Gesellschaft)

• Though they do have stingers, sea fans rely mainly on the current to bring plankton and other food particles to them. So if you have an aquarium and you want to raise sea fans, make sure your aquarium has a good current to swish the food around.

A Gorgonian called Acanthogorgia.
(Photo from the California Academy of Sciences Invertebrate Zoology & Geology)

• Sea fans also rely on the current to help them reproduce. They make their sea fan offspring in one of two ways:

1. Asexually -- a hunk of branch from the sea fan will break off, float around, and eventually land somewhere. Sometimes it lands in a favorable spot, takes root, and begins to form a new colony.
2. Sexually -- most sea fan colonies are separated by sex; that is, the male sea fans are over there, and the female sea fans are over here. So the question is, how to get the eggs and the sperm together. Sometimes both male and female sea fans will spawn simultaneously, throwing their goods up into the water and hoping their stuff happily collides (my favorite version of coral reproduction). But more often the female sea fans will snag some floating male sea fan sperm and take care of the fertilized eggs in-house, so to speak.

• Regardless of how the sea fan eggs and sperm get together, the larva, which is like a mini-branch of the coral, floats around for a while. At first it will stay near the surface of the water and if it doesn't get eaten by some predator, eventually it will sink back to the ocean floor until it finds a sandy or muddy spot it likes and digs in.
  

• Predators of the sea fans include flamingo-tongue snails and white frilly sea slugs. I am not making this up.

A flamingo tongue snail eating a sea rod. The shell of the snail is actually a plain whitish peach color. The spots you see are a living tissue that the snail pulls over itself and that works like gills, helping the snail to breathe underwater. If you collected this snail and took it out of the water, the spotted tissue would retract and it would look like a boring old shell. Don't ask me why this snail is called flamingo tongue. That's a whole other Apple.
(Photo from Reef News)

Not to be a downer or anything, but scientists predict that unless people stop messing with the reefs and producing way too many carbon emissions, 40% of the coral reefs will be gone forever in the next three years. But it's not all doom and gloom because it's not too late to stop damaging the reefs and start protecting them.

By the way, I wrote an entry a while back about coral reefs in general. It's much less specific than this entry, and the types of coral described are hard corals rather than soft like the sea fans. But if you liked this entry, you might also like that one.


Sources
Wet Web Media, The Conscientious Marine Aquarist, Sea Fans for Marine Aquaria, the Gorgonians
Florent's Guide to the Tropical Reefs
World Database of Marine Species, Universita della Politecnica delle Marche, Sea fans, gorgonians. This site has photos of all types of Gorgonians, with polyps extended and without. A great resource.
Robert Toonen, Invertebrate Non-Column: Gorgonians, Advanced Aquarist's Online Magazine
Julian Sprung, Aquarium Invertebrates: Caribbean Gorgonians, Advanced Aquarist's Online Magazine
University of the Virgin Islands, Zooxanthellae
Coral Reef Alliance, Reef Awareness
Jane Lilley, Dead Men's Fingers and Other Soft Corals, British Marine Life Study Society

Apple #326: Tilapia

Okay, remember that dinner party where we wound up talking about outer space? Well, one of the things we ate at that dinner party was some very tasty tilapia, prepared by our talented and thoughtful host.

I am not normally a fish-lover -- it's the texture that gets to me first, and then the fishy flavor, so lots of fish is pretty much off my menu. But I enjoyed the tilapia. There was a lemony sauce on top, nothing too overwhelming, but enough to give it a bit of sweet flavor. It was kind of like the fish version of chicken.

We all commented on it, complimented our host of course, wondered where it came from. (Aha, thought I. Some Daily Apple material here.) I guessed South America. Sounded like a good enough guess to everyone.

• My guess was wrong. Tilapia comes from North Africa. The most prevalent species of Tilapia is the Nile Tilapia.

• One thing to note is that some people confuse Nile Perch (Lates niloticus) and Nile Tilapia (Oreochromis niloticus). They are actually different types of fish.

Nile perch (Lates niloticus)
(Image from Wikipedia)

• Nile perch live mainly in the major lakes of Africa

• They have an almost pointy head, and they are silver with a blue tinge

• They are super aggressive eaters, and will eat bugs, crustaceans, and other fish, including its own species.

• Nile perch is very popular and has been introduced to a lot of places, but because it's so aggressive, it has either eaten or almost eradicated several species.

Nile Tilapia (Oreochromis niloticus)
(Image from the Southern Regional Aquatic Center)

• Nile Tilapia like to eat water plants and algae, but they'll also eat little tiny animals and plankton. They don't filter the plankton the way that carp do. Instead, they secrete a mucous on their gills, the plankton gets trapped in the mucous until it forms a ball, and then the fish eats the ball of mucous and plankton. Ew.

• They generally prefer warm fresh water, but they can tolerate brackish or salty water, too. They don't like true saltwater as much, though, so that means they tend to prefer living and swimming in rivers rather than in sea water. You can, of course, also raise them in ponds and tanks.

Nile Tilapia swimming around. One of the things they like to eat is mosquito eggs. So some scientists think they might be helpful in reducing the spread of malaria.
(Photo from FishChannel.com)

• They don't mind a lot of nitrites in the water, and they're very resistant to diseases that tend to wipe out other types of fish.
  

• They also spawn and grow quickly, so it doesn't take long before you can eat them. This is why lots of countries around the world are raising and eating tilapia.

• Because they grow so quickly and easily, even in poorer conditions, they can become an invasive species, too, if they are not managed properly.

A bunch of farm-raised Nile tilapia that have just been caught.
(Photo from fishfarming.com)

• But now, lots of people raise tilapia, mainly on fish farms, all over the world.

• Most of the frozen tilapia sold in the US comes from China. Some food advisory people say to avoid tilapia raised in China and Taiwan because they tend to live in waters that are more polluted than what people in the US would allow.

• But you can also get fresh tilapia that's grown up in Central America, in countries like Honduras, Ecuador, Costa Rica, and Trinidad and Tobago.
  

• It's also raised in various places in the US, such as in Virginia and South Carolina. But it's such a relatively easy fish to raise, and it tolerates tank life very well, that probably you could find fresh tilapia that comes from just about any place.

• In fact, they are so prolific that people in Indonesia used to regard them as pests, until they started eating them.

Fillets of Nile tilapia
(Photo from fishfarming.com)

• Because it doesn't have a very strong fishy flavor, tilapia is becoming increasingly popular in the US. In fact, it is now the fifth-most consumed fish in the United States, behind other favorites like tuna and salmon.

• Some chefs, though, poo-poo the tilapia. "Insipid," they call it. "Sponge-like," "flavorless," and "trash fish." These chefs are too good for the tilapia, apparently.

What grilled tilapia could look like on your plate
(Photo from MyRecipes.com's 7 Ways with Tilapia)

• Mainly, you can grill it, broil it, or bake it -- pretty much the same as with most fish.

• One easy recipe says to put the fillets on a piece of foil, give them each a tablespoon of butter, salt & pepper them, add some garlic, basil, and chopped tomato. Pour a cup of white wine over the lot, roll up the foil, stick it on the grill (medium heat) for 15 minutes until they're flaky. And that's it.

• Another one that requires only slightly more work sounds pretty good to me, too: Tilapia with balsamic butter sauce. Simmer the vinegar and some garlic in a saucepan until it reduces, for about 5 minutes, set it aside. Salt & pepper the fish, put them in a skillet with some oil, and saute them for about 2 minutes per side. Then add some butter to the vinegar sauce, pour it over the fish, and you're done.

If you prefer spicy, you might want to try the Tilapia with Spicy Mango Salsa
(Recipe and Photo from In the Kitchen)

• If you want some more recipes, All Recipes has a list of their top 20 recipes for tilapia.

And with that, I am taking my leave for a bit. I'm going off on vacation. I'll be back probably on Sunday. Not sure whether I'll be able to give you a new entry on Sunday night or not. We'll see.

In the meantime, enjoy those fireworks and watermelons!


Sources
Len Spoden, "Two Sides to Every Tilapia," The Washington Post, August 8, 2007
Aquaculture blog, Tilapia Culture, February 3, 2007 -- a great overview
American Tilapia Association, FAQs for Tilapia -- these links open separate Word documents, which in some cases are not what the links say they're going to be.
Thomas Popma and Michael Masser, "Tilapia: Life History and Biology," Southern Regional Aquaculture Center, March 1999
Randy Sell, Department of Agricultural Economics, North Dakota State University, Tilapia

Apple #228: Lemmings

The other night I walked into the middle of a conversation and was asked immediately if I knew what lemmings are. "Sure," I said, but realizing that maybe I wasn't so sure.

"I say they're a bird," one friend said, "and he says they're a mammal, and this guy says they're a reptile."

"Yeah," said the third friend. "I think they're a type of salamander."

"They're not a salamander," I said, recalling my entry on salamanders. "But I do think they're reptiles. I think they're like mudskippers, with eyeballs on top of their heads."

"We want to know," said the second friend. "Because if we're not supposed to be like lemmings, we should at least know what they are."

"That's right," said the first friend.

"So there's an Apple subject for you," said the second friend. "Tell us what lemmings are."

As you wish.

• Lemmings are a vole, a type of rodent. They look like gray hamsters. In the winter, their fur turns white.
  

The lemming: an arctic rodent
(Photo from Corel CD-ROM, used at Elizabeth Viau's site on the tundra)

• They live on the tundra or in open grasslands, mainly in Alaska and northern Canada along the coast.

• They reproduce very quickly, betting that their sheer numbers will help them survive predators and the severe arctic weather. Lemming females can reproduce every 20 days, with litters of 6 to 9 babies each cycle. The young females become sexually mature when they're only one month old, so the number of lemmings can get to be exponentially high very fast.

In the winter, a lemming's fur turns white
(Photo from Arthropolis)

• They are food for a lot of predators, but because of their extreme rate of reproduction, they can get over-crowded fairly quickly. When they reach a crucial level of overcrowding, they will disperse, embarking on a migration to find more space.

• Sometimes that migration can get pretty frenzied, and since they often travel along the coastline or on the edge of embankments, sometimes the lemmings knocked each other into the ocean.

• Also if the food supply is scarce, lemmings may kill other lemmings to lessen the competition for food, or to create more food; that is, they may eat each other.
  

• Sometimes they head into the water, thinking they're crossing a river, but it turns out to be the ocean, and they drown.

• A little dense or even murderous they may be, but suicidal they are not.

• How then, did the lemmings-are-suicidal myth get started? Mainly from a 1958 Disney movie called White Wilderness.
  
  
  Disney's White Wilderness was part of a series called True Life Adventures. White Wilderness is contained in this collection.
  
  
  
• To make the movie, filmmakers bought some lemmings from Inuit children and then took the animals to landlocked Alberta, Canada. Lemmings do not live in Alberta, preferring colder climes that are not landlocked.

• The few lemmings were filmed on turntables from various angles. Those images were reproduced to give the illusion of a crowd of lemmings. They were then taken to a cliff overlooking a river and herded into the water -- some say "thrown off the cliff" -- while the cameras rolled.

• In the finished film, the voiceover says that the rodents are "carried along by an unreasoning hysteria," which results in the animals "casting themselves out bodily into space," when in fact people were flinging the lemmings into the water at the time.

• In other nature documentaries, filmmakers had difficulty capturing a lot of live lemmings on camera. More often, they were able to find lemmings that had swum out into the ocean, believing it to be a river, and drowning, or other lemmings being pushed off a cliff by their fellows during the mad dash to migrate.

• Many cartoons have also been drawn showing lemmings dashing headlong into the sea, including cartoons by none other than Gary Larson. I'm not allowed to reproduce that cartoon here, but you can look at it on this page.

This lemming says, "Don't believe the hype!"
(Photo from University of Wyoming's Population Ecology lecture notes)

• People have seen enough of these sorts of images to develop the notion that lemmings jump willy-nilly into the sea to drown themselves, when in fact, the lemmings are being murderous or careless or just dumb.

• (Hmm, in believing this Disney movie and other images we've been shown, are we not behaving like the mythical lemmings we have ourselves created?)

• In any case, though lemmings are not suicidal, the attributes they seem to have are not especially admirable. I'd advise against such similarly murderous, cannibalistic, careless, or stupid behavior.
  

Sources
Snopes.com, White Wilderness
Elizabeth Anne Viau, California State, The Tundra
Canadian Fauna, Lemming (Lemmus Lemmus)
Riley Woodford, Lemming Suicide Myth: Disney Film Faked Bogus Behavior, September 2003
April Fools' Science Fables, Lemming theory jumps in in the lake
IMDB, White Wilderness
Chris Clarke, "By Design," New Internationalist, Issue 308