Category: Invertebrates


Umwelt

tick

A tick crawling along the ground. Image taken at Ano Nuevo nature reserve.

Imagine for a moment that you were a tick. What would your world be like? A tick’s world consists of only 3 sensory cues. Three. First, they can detect light. This helps them to climb up tall grass to get higher off the ground and in a spot they are more likely to find a passing meal.

tick

A tick now climbing up some blades of grass. Image taken at Ano Nuevo in California.

Once high up on a blade of grass, she waits for her second cue, the smell of butyric acid-a mammalian chemical by-product. When this smell comes by, she knows food is near and will drop off of her plant. An individual tick has been known to wait as long as 18 years for this precious cue.

Her last cue is warmth. Warmth indicates where blood is running close under the skin. Finding a warm spot, she burrows in, drinks the blood, drops off her host, lays her eggs and dies. She can’t taste the blood she’s been waiting so long for. In fact, she will drink any fluid that is the right temperature.

That’s it. Three things a tick can sense throughout its entire life. That’s its Umwelt, which is a term that means “the surrounding world” and is used to describe the unique and  limiting sensory world of every single animal species. Even within a species, individual animals can perceive the world differently.

A ticks Umwelt is incredibly simple. However because of this simplicity, her actions are unfailingly certain, with no distractions.

It’s wonderful to imagine what the world must be like to other animals. What do they experience that we don’t? What can we sense that they cannot? I plan to go into this in more detail in future posts. For the moment, consider our Umwelt and how very limiting it is. Even within our species, each of our brains is interpreting the world around us in a slightly different way. Sometimes before a stimulus even gets to our brains the hardware that captures it can be different between individuals. Take for instance our eyeballs. If we remove technology like glasses and lenses, think of how differently human beings would see the world. Even with those glasses and lenses there are differences.

We rely so much on our senses, it’s easy to imagine that the world holds only what we can experience. A great example of this is the discovery of color blindness. Although almost 10% of humans are color blind, color blindness wasn’t discovered until 1793, when a chemist named John Dalton, who had been working for years on colors of chemical compounds, realized that he himself was color blind. Imagine! It’s so easy to assume that everyone else senses what you do!

So next time you say the sky is blue and your friend says its purple, maybe they’re not being argumentative, maybe they’re telling the truth!

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silverfish

A fuzzy, little silverfish crawls along the bathroom wall of my old house. Image taken in San Francisco.

Have you ever gone to the bathroom at night and noticed a small, silvery, three-tailed invertebrate running for a crevice or hiding spot? Or perhaps under your kitchen sink or in your basement? Maybe even behind your bookcase or in your dresser? If so, you have silverfish! Although most of the time we come across these animals in our homes, they are more typically found outdoors, in leaf litter or in soil.  Still, they adapt quite well to living in our houses.

Although very cute and harmless to humans, silverfish can be quite a pest. Some of the yummy things in your home that they like to eat include flour, damp textiles, book bindings and book glue, magazines, newspapers, sugar, breakfast cereals and their boxes, insulation materials (!) and even wallpaper paste. They can also live several months without eating at all. Once they’ve established themselves in your home, they are very difficult to eradicate. But don’t worry too much; it takes a large population and a lot of time to do any serious damage.

Although I chose to live in harmony with my silverfish friends in San Francisco, I was very careful to check all of my belongings to make sure none found their way to my new apartment in Portland. So far, so good! I haven’t noticed any yet.

Death, Taxes and Cockroaches

Madagascar Hissing Cockroaches

Madagascar hissing cockroaches. Image taken at the California Academy of Sciences.

There are over 4,000 species of cockroaches. While the word cockroach generally conjures up images of fast critters, scurrying along a kitchen counter, out of these 4,000 species, less than 1% are actually considered pests and inhabit homes. I’m sure you’ll agree with me when I say that’s enough.

So, first off, let’s talk about that small minority. There are 6 species that are pest species and of those, 3 are the ones most encountered. They are the German cockroach, the Oriental cockroach and the American cockroach (all can be found in North America).

The German cockroach is generally considered the worst, mainly because of its size. They are so small that they can easily creep into buildings and are hard to get rid of. These roaches are the reason you hear about cockroaches surviving nuclear blasts and being around when all the rest of the world is destroyed. In the 1960’s, experiments were done with these roaches where they were exposed to more than 5 times the amount of radiation that had resulted from Hiroshima-and survived! Although this is not the same thing as surviving a nuclear blast, it is still impressive. Now imagine someone chasing them around with a little aerosol can. Ha! Yeah, right. These cockroaches are generally thought of as dirty little creatures and while they do groom themselves, they can transport bacteria from places like garbage cans to sanitary places that you wish they wouldn’t, like your kitchen. Because of this, they can spread diseases like food poisoning, dysentery and diarrhea and having large populations of these roaches is thought to contribute to problems like asthma. The German cockroach can also emit secretions that smell like food, in an attempt to attract females, whether or not they are interested in mating.

The Oriental and American cockroaches prefer damp areas-pipes, drainage systems and sewers. The American roaches are the largest of the pests and therefore have a harder time existing in areas where they are easily spotted. There was one study of American cockroaches that found 22 species of bacteria, virus, fungi and protozoa that are known human pathogens, plus 5 species of parasitic worm in field collected animals.

So the thought of cockroaches as dirty, disease spreaders is really not entirely unfounded. But those that are fit into a comparatively small category of a really diverse group of animals and many of those animals play a central role in their ecosystems. So, now I’m going to go over just a little bit of cockroach diversity.

Roaches can range in size from the giant rhinoceros cockroaches (a.k.a. giant burrowing cockroach) from Australia, which are burrowers and are about 8.4 inches, to the teeny tiny wheeler ant cockroaches, which live in leaf-cutter ant nests and are only .1-.2 inches. Some can produce repellent chemicals that can cause temporary blindness or skin rashes.

Wood cockroach

Giant cockroaches (Blaberus giganteus). Image taken at the Insect Discovery Lab.

For example, when annoyed these giant cockroaches emit a substance that make them smell peppery. Some cockroaches make egg cases, that remain attached to the female’s abdomen until she can find a safe place for it (Ensign wasps can deposit eggs into the capsules while still attached to the female. The wasp young will consume the eggs.) Other cockroaches are live bearers.

Hissing cockroach

The Madagascar hissing cockroach is one type of live-bearing cockroach. Image taken at the Insect Discovery Lab.

The Madagascar hissing cockroach is an example. The female will extend the egg case from her body, but then pull it back in to be brooded and the baby roaches come out alive. The parents and young will stay in close contact for long periods afterward. They are also an example of a species that doesn’t have wings, while some other species do. Those that do fly still tend to get around more often by running anyway. Different species of cockroach can run from 2-3 mph. That’s quite impressive, when you take their size into account. And they’re great climbers. This hissing cockroach can even scale smooth glass.

Some types of tropical roaches also use sexual mimicry to outroach a dominant male. When the dominant male opens its wings to attract a female, the impersonator behaves like a female and mounts his competitor. This leaves the dominant male vulnerable and the impersonator will bite the wings off of his opponent, who then scurries away in defeat.

The hissing cockroach has some interesting mating behaviors as well. First off, you might notice that in the image above, the cockroach has two large bumps over what looks like its head (but is actually a protective covering over his head). As you can see below, the males have larger bumps and thicker antennae than the females.

Hissing cockroaches

A male (left) and female (right) Madagascar hissing cockroach. Image taken at the Insect Discovery Lab.

This is because the males will use their horns to fight. The males will ram each other to fight for territory. And of course, these guys get their name from their characteristic hiss. While they’re fighting, the winner seems to hiss more. They hiss by pushing air out of their breathing holes (called spiracles), and they have 4 types of hisses, 3 of which are made only by the males. One type of hiss is to court a potential mate. Another is to defend its territory, which may have several females. It’s a warning to an intruding cockroach. Their hiss also conveys their size and can be used to assess opponents. A third hiss is a battle cry, used when a male disregards its territorial hiss and tries to move in on the harem. And the last hiss is made by all roaches, male and female and signifies annoyance.

These little roaches are great and they can be found in just about any live insect exhibit, often with young roaches crawling around as well. And like the vast majority of cockroaches, they are incredibly important to their ecosystem. But let me explain how.

When you think of the rain forest and all of the beautiful trees, plants, flowers, fruits, shrubs, vines, mosses, etc., it’s easy to assume that the dirt all of this is growing out of is full of nutrients. But it’s not. Most of the nutrients have actually been sucked out of the soil and are in the plants themselves. The dirt has almost none left. That is, until you cue the cockroaches and the other recyclers in the rain forest.  They take the dead or decaying trees, plants and organic matter (including poop) and break it all down into basic nutrients again, so that the living plants and trees can take them in. Without roaches and animals like them, these valuable nutrients would be locked away and the rain forest would not be able to sustain itself.

Cockroach

Another one of the rain forest’s recyclers. Image taken at the Insect Discovery Lab.

A few species of cockroaches have extra help with their important job. They have a symbiotic relationship with protozoa in their gut that breaks wood down into sugars. Needless to say, they need to pass this helpful organism on from one generation to the next. So, after each molt, the young roaches will eat some of the groups droppings, which will then reinfect them with their helpful partners.

Of course, I appreciate roaches for their important roles. But truthfully, that’s not why I am completely astounded by them. Nope, that is because of their resilience. I have to admire these creatures for their sheer adaptability. I am a fan of the survivors. I mentioned earlier that they can survive radiation poisoning. But that is really just the tip of the ice burg. They have developed immunity to pesticides. They can survive for up to one full month WITHOUT THEIR HEAD!!! Do you remember that going around in a chain e-mail way back when? That is actually a fact. Decapitated roaches continue about their business until they dehydrate. There are a lot of adaptations that make this possible [no blood pressure (won’t bleed to death), breathes through spiracles, which are little holes on its body (like all insects) and has nerve clusters in each body segment, so it can survive without the brain in its head.] It’s so simple and so sophisticated at the same time. It’s like a little recycling machine.

That’s probably why they have been around so long. The largest roach fossil was found in Ohio, in a coal mine, and dated to 300 million years ago. Other than the size, there are only a few tiny details that have changed between fossil roaches and those that are alive today.

On a final note, the geneticist in me insists on pointing out that an observation of the roach Blatella germanica revealed that with a small genetic change, the roach will grow wings on its first thoracic segment, which no modern insect has, but that does appear in some of the earliest winged fossil insects. I know this could be a discussion in itself, but I’ll just leave you to ponder it for now, as this is already a really long post.

And for a little bit of cockroach nostalgia:

Tale of Melibe, the Sea Slug

 

Melibe nudibranch

A Melibe nudibranch is filtering for crustaceans with its unique hood. Image taken at the Monterey Bay Aquarium.

 

Yet another sea slug! I just can’t get away from them-I’m hooked! And who can blame me; this groups of animals has it all. Such a thorough example of adaptation at its finest can never fail to intrigue scientists or enthusiasts like myself.

Take this sea slug for example. First of all, those flat, paddle-like branches coming off of its body are called cerata. Sea slug cerata can have many functions, including gas exchange, color changing for camouflage, holding the stolen nematocysts to sting predators (See my first sea slug post for more information) and in some cases they contain part of the digestive tract. Comparing the cerata of different groups of sea slugs has been said to be similar to comparing the wing of a bird to the wing of a bat-they are that diverse in function and appearance. Anyway, if a predator grabs this sea slug’s cerata, it can detach the appendage from its body to get away. It will actually pull in its large “hood” to reduce drag and swim away. And later on, it will simply regrow its cerata. Regeneration. Now that’s part defense, part super power.

Not that the sea slug has to worry about many predators. The only animals it really has to worry about are kelp crabs. That’s because kelp crabs aren’t bothered by another defense of theirs-a toxic secretion that makes these nudibranchs smell like watermelon. Mmmmmmm….poisonous watermelon.

This genus of sea slugs are also unique because of their “hood,” the big, roundish, tentacle covered part of its head. Most sea slugs eat using a radula, which is like a scraping tooth. This sea slug however…well, look:

It uses its oral hood to filter small crustaceans out of the water. The hood is surrounded by sensory tentacles that help it to grab small food and pull it in toward its mouth. It’s pretty weird, but also beautiful and mesmerizing. And even though this looks really similar to a jellyfish, this animal is more closely related to an octopus than to a jellyfish.

I guess the last thing I want to show is this sea slug’s eggs. If you remember from the first post, I mentioned that sea slugs lay their eggs in beautiful ribbons, so here are some more see slug eggs attached to a kelp leaf:

 

sea slug eggs

Sea slug eggs attached under a kelp leaf. Image taken at the Monterey Bay Aquarium.

 

And there you have it! Yet another unique, amazing, beautiful sea slug.

 

Giant Thorny Phasmid

This giant thorny phasmid enthralled us with her most amusing antics. Image taken at the Insect Discovery Lab in San Francisco.

 

Walking sticks are most known for their amazing camouflage. But their camouflage often involves a lot more than simply their good looks. While having the shape and coloration of a leaf, like the one pictured above, or a stick, like the one shown below, certainly helps, it’s really just the beginning.

 

Stick insect

Stick insects can look like leaves or sticks. In some species, the females look like leaves and the males like sticks. Image taken at the Insect Discovery Lab.

 

Even their eggs are camouflaged, looking like plant seeds. But in addition to this, they also have behavioral adaptations that help them blend in or in some cases, mimic other animals.

For example, obviously, if you are trying to mimic a stick, then remaining still most of the time is pretty important. But, these animals take it a step further and will even flex their legs in such a way that keeps them in exact motion with the plant, which may be gently swaying in a breeze. Brown nymphs, or young walking sticks that haven’t reached the adult stage yet will hang from a twig and if they are disturbed, they will drop like a dead leaf. They’ve even been shown to hold their legs at exactly the same angle from the tree that the twigs around them are. All of these are behaviors that help keep them invisible to potential predators. That’s probably why these guys are in the Order Phasmida, which is from the Greek phasm, meaning phantom or apparition. They vanish from sight. Here’s a young insect among leaves, so you can see how well their camouflage works.

 

stick insect

A young stick insect clings to some leaves, which provide camouflage as well as food. Here's a challenge-Can you find a cuter baby bug? Image taken at the San Francisco Zoo.

 

Still, some species can also mimic other animals. For example, Australian walking sticks are thought to curl their tails when discovered and threatened, perhaps to appear like a much more threatening scorpion.

 

Australian walking stick

This young Australian walking stick is curling its tail, perhaps to mimic a dead, curled leaf, or perhaps to mimic a scorpion. Image taken at the Insect Discovery Lab.

 

I have actually come across conflicting ideas about this strategy. On one side, some say they are not mimicking scorpions, but dead, curled up leaves. Since scorpions are on the ground and they generally live in trees it wouldn’t make sense to mimic them. But would the predator know that? Perhaps both ideas are in play. On a side note, these guys as adults also have wings that are brightly colored on the inside, which they can flash and startle predators with as well.

Another species of walking stick that mimics another invertebrate is the Spiny leaf insect, aka macleay’s spectre stick. In this case, when the insect lays its eggs, the eggs have little knobs on them which attract ants. The ants will carry them to underground nests, where they eat the knob, but leave the rest of the egg alone. Being in this underground nest grants them protection from predators. 1-3 years later, the eggs will hatch and the nymphs will emerge looking and behaving exactly like the red-headed black ants, until they molt.

The spectre stick is not the only walking stick with an interesting reproductive strategy. For example, there are a couple of other species where the females eject their eggs from their abdomens and scatter them about. Cyphocrania gigas can expel her eggs almost 20 feet away! By scattering their eggs, they reduce predation and competition between siblings.

Also, many walking sticks can reproduce asexually! That is, the females don’t have to mate with a male at all to produce offspring. It’s the true virgin birth. In some cases, it takes longer to reproduce asexually, but it’s still possible. For some walking sticks that do this, males are often hardly ever found.

Another interesting reproductive behavior-generally a male walking stick finds his mate by scent and then climbs onto her back to mate. The male will remain there for hours at a time, staying on the female so that no other male will have a chance to mate with her, thus insuring her offspring will be his. The much larger female seems to hardly notice, as she goes about her daily business as if nothing unusual is happening.

However they do it, if the eggs survive, they hatch and a new walking stick begins its life. The walking stick will go through several different molts (6-7 seems to be the general range) until they become adults. The Australian walking stick, might eat its exoskeleton after each molt and tend to get darker with age. The stage of life of an insect (actually arthropods, the larger group including insects) between molts is called an instar. Below are pictures of a couple of young walking sticks in different instars, so you can see some more juveniles.

 

walking stick

A young walking stick. Image taken at the Insect discovery Lab.

 

 

walking stick

Two more young walking sticks. Image taken at the Insect Discovery Lab.

 

These are the same species, just different sexes and instars.

Now here’s a different juvenile walking stick. Notice something missing?

 

Walking stick

A young walking stick missing its leg. Image taken at the Insect Discovery Lab.

 

Young walking sticks will give up a leg to a predator if it has to in order to get away. But this is not the tragedy it seems to be, because after several molts, they can actually regenerate their limbs! So none the worry for this little guy; he’ll be good as new before he’s an adult.

 

giant thorny phasmid

A giant thorny phasmid, crawling along my camera. Image taken at the Insect Discovery Lab.

 

Now this picture is of the giant thorny phasmid, aka the Maylayan Stick Insect. This is the same bug as in the first picture, but I included this picture to show the scale (and her useless wings). You can see that she is roughly the size of my hand, full grown. Now, that’s a big insect. But not the biggest. I wouldn’t be doing stick insects justice if I left out the fact that the largest insect discovered in the world so far is a phasmid. They can range in size from a small half of an inch to a record 1.86 feet or 22.32 inches. Not including it’s legs, it’s 14 inches long. And yet, I suppose if there has to be an almost 2-foot long insect, I’m glad it’s a walking stick. They are fascinating, pleasant-to-be-around insects. This girl shown above goes to schools and meets kids on a regular basis, to teach them about insects and the rain forest her relatives live in.

Well, just in case you haven’t had enough of stick insects yet, here is a cool picture of one nomming a leaf. Stick insects eat plants. Is that cannibalism?

 

walking stick

A walking stick nomming a leaf. Image taken at the San Francisco Zoo.

 

Now, you might think that a plant-eating animal that sits still and hides all day poses no threat to potential predators. But a few walking sticks do have some other defenses. For example, some have giant spines on their legs, like this one shown below. They will use these spines as a defense, but also in competition between males.

 

Phasmid's spiny legs

The spiny legs of a phasmid. Image taken at the Insect Discovery Lab.

 

Ouch! But that’s not the winner. No, I think the award goes to the musk mare, aka the two-striped walking stick. This insect can shoot out a chemical spray with pretty high accuracy. If they get their potential predator in the eye, they can cause temporary blindness and in extreme cases, they can cause corneal damage. And they can spray more than a foot away.

Anyway, this post is just a glance at a few of the ~3,000 known species of stick insect, and just a small fraction of the cool things they can do. If you’d like to learn more, a good place to start is with the Australian Museum’s site, which discusses several species I didn’t mention here. Also, many zoos and aquariums have stick insects, so checking out your local facilities might yield some cool experiences and observations as well.

And last, but not least, special thanks to phasmid wrangler Will Mckennet for raising these animals since they were eggs, and sharing them with us.

Scallop

A scallop relaxing on a rock. Scallops will hang out on the surface of the ocean floor rather than burrowing like their clam cousins. Image taken at the Aquarium of the Bay.

This unassuming little bivalve is one of over 300 species of scallop. These creatures are not only interesting and unique among the shellfish, but they also play an important part in the human world as well.

Scallops are the only shellfish that can move around using jet propulsion. They don’t hide buried in the sand or attach themselves onto hard surfaces (although the juveniles will attach until they are big enough to not be dragged away by strong currents), but rather they lie loosely on the ocean floor.  If danger is near, they will swim away by clapping their shells together (video of scallop swimming here). In order to clap their shells together, they use a very strong circular muscle called the abductor. This muscle is the part that humans will eat when they’re having scallops. It’s a really good food source that’s high in protein, vitamin B and selenium and low in fat.

And we do eat a lot of scallops. In 2008, in the United States alone, 53.5 million pounds of Atlantic Sea scallops worth $370 million was harvested (That’s just 1 type of scallop!). And the good news is that scallops are a good choice for sustainable seafood. Despite the large amount of scallops we’re pulling from the ocean, because of serious declines in the scallop population off the east coast in the early ’80s, the fisheries are now regulated. For example, only scallops above a certain size can be taken, so it’s likely each scallop has had a chance to reproduce before it’s harvested. This combined with the fact that these animals reproduce very quickly (1 scallop can produce up to 270 million eggs in its lifetime) has led to a wonderful come back, as these animals are now abundant again and even spreading their range. This is a good example of how harvesting sustainably has prevented the crash of an entire fishery and led to the protection of a valuable animal, that will continue to be valuable (in a number of ways, as this post will show) for years to come if we continue with our healthy practices. Consider this- if we had continued to overfish these animals 20-30 years ago, would we still have this lucrative industry today, when our economy needs it the most? Just a note, it is still considered better to eat farmed scallops if you have the option. They do use dredges to gather scallops and those can result in by-catch. However, the regulations in place prohibit using dredges in certain areas and in certain seasons to minimize by-catch, so if farmed scallops are not available, wild-caught scallops are a good alternative.

Aside from their economic and nourishment value, these animals are also important in research. As filter feeders, they are useful in evaluating the environmental impact of petroleum spills. But in addition to that, there is some other research going on involving an unusual feature of scallops.

Scallops

An open scallop. Look closely at the little dots along the edges of its mantle, or right near the edges of its shell. These dots are the scallop's eyes. Image taken at the Aquarium of the Bay.

Scallops have primitive eyes all long the edges of their mantle, right near the rim of their shells. In the picture above, you can only see the eyes on the bottom rim, but they do have them on both the top and the bottom. These eyes can detect light and dark, like the shadow of a predator, as well as movement. If it senses danger, it can close up into its tough shell or swim away. Their eyes have a retina and two types of photoreceptors, which are the cells that change light information to chemical information that your nervous system can interpret. So why am I going on about scallop eye biology? These eyes have some similarities to ours, but if something happens to a scallop eye, it can regenerate its photoreceptors. As we work to understand this better, maybe we can find the key to creating or saving photoreceptors in humans who are losing their vision from degenerative diseases. And there you go. Scallops, perhaps one day helping people not go blind.

Orb spider

The golden orb spider. The smaller spider is the male. Image taken in Manzanillo, Costa Rica.

This majestic creature is a golden orb spider, so called not because of its golden yellow and black appearance, but because sometimes, not always but sometimes, they make a web that is a lustrous gold color. We don’t know why, although one hypothesis is that the golden web might hold up better against sunlight. In the picture above, the large spider is the female, while the smaller one is the male. The females of these species are known cannibals, so he had better be careful. One study reported that at least some of the time, larger males were more likely to be eaten than smaller ones, suggesting a reason for why the males are so small compared to the females.

The reason why I chose to highlight this spectacular spider is because of the amazing material she produces to build her web and to catch prey-her silk. Of course, other spiders and invertebrates can also produce silk, but the silk from golden orb and black widow spiders is special (we’ll talk about black widows in another post). As far as we know, their silk is the strongest material, natural or man-made, in the world when comparing strength using the same weight of each material. Their silk is roughly 5 times stronger than steel and 3 times stronger than Kevlar. (An individual spider can make up to 7 different types of silk. The strongest is the drag line silk, which is the silk that makes the frame and spokes of their web.)

It has been calculated that a single strand of their silk that is the thickness of a pencil can stop a 747 in flight and that a 2cm strand should be strong enough to repeatedly lift 2 metric tons.

As you can imagine, this stuff has had scientists drooling for decades now and producing a synthetic spider silk has become the holy grail of material science. Using real spider silk has proved difficult because, as I’ve mentioned before, the spiders tend to eat each other. There has only been one large golden cloth made from real spider silk, and it took over 1 million spiders and several years to produce. It is displayed at the American Museum of Natural History in New York.

Some of the possible uses for a good synthetic spider silk include earthquake resistant bridges, sutures and bullet proof vests. But my absolute favorite possible use for spider silk was recently published by the Journal of Experimental Biology and it involves a different property of spider silk other than its strength. Spider silk contracts when it’s wet and expands when it’s dry. If you took a piece of drag line silk and wrapped it around your finger and then placed your finger under water, the silk would contract so much that it would cut off the blood supply to your finger. This important feature is probably what holds a web in place when it rains and adds extra weight to the web. Given that this material expands and contracts, one potential use is to make a humidity powered biomimetic muscle. That’s right, an artificial muscle that has the potential to be 50 times stronger than human muscle and is powered by water. Some of the suggested uses for this muscle include making compact actuators for robots, sensors and green energy production.

And what does the spider use her web for?

Golden orb spider

A golden orb spider descending on her prey. Image taken in Manzanillo, Costa Rica.

More specifically?

Special thanks to my husband Trey Jackson for filming, editing and donating this incredibly cool video.

Nudibranchs: The Sea Slugs

sea slug
Image taken at Aquarium of the Bay in San Francisco

The world of sea slugs is an amazing one.  First off, they are absolutely, stunningly gorgeous.  The one pictured above is comparatively subtle, with its pretty frosty spots, but sea slugs come in every color of the rainbow with fantastic and startling features.  Check it out, right now.  Go on.  Google image nudibranch and see what fascinating creatures pop up.  I’ll wait…

Finished?  Told you so.  Alright, so these animals are beautiful.  But they are even beautiful as eggs.  That’s right, they lay their eggs in gorgeous ribbons that look to me like underwater flowers.

egg ribbon
Sea slug egg ribbon.  Image taken at Aquarium of the Bay.

But beauty is not the reason why sea slugs are my favorite animals in the ocean.  No, that would be because of the multitude of ways these animals have to defend themselves.  So imagine for a moment that you decided that a porcupine would make a tasty treat.  You caught a porcupine and ate it.  And then all of a sudden you grow quills out of your back.  It’s absolutely absurd I know, but sea slugs do something similar.  Some species of sea slug eat sea anemones, which are animals that are related to jellyfish and like jellyfish, they have stinging cells called nematocysts.  (See a video of nematocysts firing here.) But the sea slugs don’t get stung by their prey.  No, instead as they make a meal of the anemone, the stinging cells pass through their system undischarged and then pop out of their back, so that the nudibranch has now essentially stolen its prey’s defenses to protect itself.

Other species of sea slug eat sponges instead.  Sponges are animals that are often poisonous, but the sea slug is not at all deterred by the toxins in their prey.  Once again, they will steal their prey’s defenses and instead of being poisoned, they will store their prey’s toxins and become poisonous.  Sponges are also often brightly colored, a warning to other organisms that they should be left alone.  When a sea slug eats its sponge prey, it will not only take their toxins, but it will steal their pigments as well, so when they are on their host sponge, they will be perfectly camouflaged and when they move away, they will exhibit wonderful, bright warning colorations.

Last, but not least, there are at least 2 species of sea slug that are pelagic, which means they float in the water column instead of crawl on the bottom of the sea floor.  One of these species actually eats the portuguese-man- of-war, a highly venomous animal (or rather, 4 types of animals working together) that is also related to jellyfish.  Pretty impressive, huh?

And I didn’t even get into the regenerating sea slugs or the sea slug that can photosynthesize!!  That’s right, the first animal ever found that can make food using only sunlight, like a plant.  (Note that it is not simply storing algae in its body and stealing the food the algae is making.  This is true photosynthesis.)

If you’re interested in learning more about sea slugs, the Australian Museum has this wonderful forum to start you off.