Monsters Mini-Post: On Pitcher Plants and Symbiosis, or, A Meal Is Better When Shared

Compared to Venus flytraps, which clamp their jaw-like leaves around flies and other small, wriggly bits of prey, the various pitcher plants in existence must seem like pretty benign carnivores. Their way of capturing prey strikes me as a bit like windmill fighting: can they help it if juicy insects and ripe-looking amphibians happen to tumble into the pits of digestive enzymes waiting at the bottom of their pitcher-shaped leaves?

In fact, pitcher plants don’t consume every organism that ends up in the pit. Some of those organisms actually help pitcher plants process the other creatures they’re about to eat, somewhat like parents who cut their children’s food for them, though slightly more savage.

Nepenthes is a genus of pitcher plant found primarily in the southeast Pacific. Each leaf starts with a thin tendril at the tip, then inflates like a long balloon until finally, at maturity, a flap of leaf material at the tip opens, and a pitcher is formed.

Pitchers in general are excellent for holding liquid, and those belonging to the plants of genus Nepenthes are no exception, though the sweet, attractive nectar and the digestive enzymes that they produce differ substantially from the iced tea you might pour yourself on a hot summer day.

As effective as the digestive juices that Nepenthes make (capable, in some species, of taking out entire mice) are, the digestion process can always stand to go more quickly. Some Nepenthes have tiny hollow chambers in their stems where ants can make their homes. Instead of falling into the pitchers, the ants snag other insects attracted by the nectar. The ants are sloppy eaters, which is a good thing for Nepenthes, as the stray insect crumbs slip into the pitcher and get digested much sooner than an entire insect would.

So some ants and some pitcher plants make good matches. Others, not so much. Sarracenia is another genus of pitcher plant; some of its member species grow from the grounds of peat bogs in North America (including Illinois’ own Volo Bog). A Sarracenia‘s pitcher looks different from that of a Nepenthes, in part thanks to a flange running the length of the leaf that creates a stream of nectar. Ants climb the leaf and follow the trail, which leads to the edge of the long, tall pit, and—whoops, in they go.

That’s not to say that Sarracenia species can’t play nicely with others. The larvae of some insects, such as the blowfly, live inside the pitcher and feed on partially digested remains, while bacteria in the water that also collects in the bottom of the pitcher help get that digestion going in the first place.

Though they pose a threat to some living creatures, pitcher plants hardly are isolated organisms, at least within a habitat. In the case of Nepenthes, our evolutionary tree suggests otherwise, as Nepenthes are believed to exist much in the same form that they have for millions of years. In other words, the Nepenthes genus has no close relatives.

That’s okay, little pitcher plants. At least the ants seem content keeping you company.

Monsters Mini-Post: On Caterpillar Defense Mechanisms, or, Sticking It to You

Some caterpillars possess amazing defense mechanisms, the kind that exist to make parents and guardians forever fretful when their kids go out to play. Other caterpillars mimic bird poop. I guess the phrase “different strokes for different folks” applies to the non-folks of the animal kingdom as well.

The photo that inspired today’s post.

Caterpillars are the larval forms of both moths and butterflies, squishy little worm-like creatures that emerge from eggs. Their squishiness makes them incredibly attractive to several members of the animal kingdom including birds and squirrels that, like me around midnight, are always on the lookout for a snack that’s easy to eat.

So to become a bit more difficult to eat, several species’ caterpillars have evolved features along their bodies that discourage other animals from poking at them, usually through the always discouraging use of toxic chemicals. The larval forms of such frequent flyers as the Io Moth, the Buck Moth, and the Hag Moth all have bodies lined with stinging hairs and quills that are connected to poison sacs. These hairs can break skin, allowing the toxic chemical to seep beneath them. Humans who get stung by these caterpillars may experience symptoms ranging from minor irritation to everybody’s favorite, intestinal discomfort.

Given how most people feel about having a churning sensation in their lower abdomens, it’s understandable that a lot of people avoid touching caterpillars just to be on the safe side. The majority of caterpillars are not stinging caterpillars, though. Unlike the stinging caterpillars listed above, others have bumps on their bodies that appear harmful but really are just for show.

One such caterpillar is the Black Swallowtail. During some of its larval stages (and larval stages are called instars, in case you were wondering, since science has names for everything), the Black Swallowtail’s body is lined with orange bumps that protrude from the surface. They look dangerous, because often in nature red and orange are used as colors that warn predators that they’re hunting something that will seriously screw them up, but Black Swallowtail caterpillars are considered by some people one of the best caterpillars for budding entomologists to try to raise.

So how do Black Swallowtail larvae stay safe? Well, they do have one protrusion that actually does mess with other animals. It’s called an osmeterium, and it’s a Y-shaped horn located at the back of the caterpillar’s head that pops out when the little squirmster is frightened and gets retracted when it once again feels safe. The osmeterium shoots a musty-smelling liquid that, while not harmful to humans, is tinged with a distinct whiff of eau du displeasure, enough to suggest that backing away is a good idea.

But before the osmeterium even comes into play, the Black Swallowtail caterpillar defends itself in another way: similar to the Tiger Swallowtail caterpillar, during its earlier instars, its body bears a splotchy white marking right in the middle. Does this white mark carry the same suggestion of poison that red body markings do? Nope. Does it make the caterpillar look like an unappetizing piece of bird poop that squirrels and other animals are likely to pass over without a second thought? It sure does!

No one ever said that survival can’t be crappy sometimes.

On Seed Dispersal, or, One Day I’ll Fly Away—Or Be Launched, Whichever

I use witch hazel extract on my face every night. It’s derived from the leaves and bark of the common witch hazel plant, Hamamelis virginiana, and in addition to cleaning the skin is supposed to help relieve it of irritation. In light of witch hazel’s calming properties, I guess it’s a little funny that a witch hazel plant starts out, very literally, with a bang.

For a plant to produce offspring and continue that beautiful circle of life that Elton John sang about, it has to send seeds out like children into the big, bad world, a process known as seed dispersal. And just as some parents and caretakers allow their children to keep living at home after graduation, maybe staying in the basement or the pool house, while others practically pack their kids’ boxes and suitcases for them, plants go about seed dispersal in any number of ways:

The photo that inspired this post.

• Letting gravity take its course

• Encasing their seeds in tasty fruits for animals to eat so that the seeds will later be, um, deposited (seed dispersal plus, now with a fertilizer bonus)

• Attaching lightweight structures that allow the seeds to drift serenely on the breeze

• Launching them violently into the surrounding environment

That last option probably sounds made-up. It isn’t. Witch hazel seeds develop inside of a capsule that bursts at maturity. Like a circus daredevil spewed from a cannon, each seed ends up shot about twenty to thirty feet away from the parent plant. The capsule makes a popping sound upon bursting—or a bang, to go back to where we started this.

It’s nothing like the method of seed dispersal that many trees here in the Midwest employ. Wind dispersal seems more appropriate for a plant that’s used to make a soothing extract. The way that whirlybirds or helicopter seeds like the ones seen in the photo above (the technical term for a winged seed like these is a samara, presumably because “whirlybird” never stuck in scientific circles) simply flutter to the ground perhaps offers a greater sense of enchantment than the botanical equivalent of cannon fire. Plus, as mentioned before, all the other plants are doing it: various trees including ashes, the winged elm (naturally), and most conspicuously maples all produce winged seeds.

So why doesn’t the witch hazel plant give in to peer pressure? Well, as helpful as winged seeds are in spreading a plant’s offspring far and wide, that huge range of dispersal (we’re talking hundreds of feet here) comes with certain trade-offs:

1. Not every seed is guaranteed to land somewhere hospitable and grow, so the parent plant spends a lot of energy producing seeds that will never germinate.

2. In order to be light enough to dance on the spring breeze, winged seeds aren’t packed with as much nourishment as, say, the seeds packed into fruits are. As a result, some will be too poorly nourished by the time they land to sprout.

3. Kids like to pick them up and toss them into the air, at least where I grew up, because it looks really neat (see trade-off #1).

No doubt that witch hazel’s exploding seed pod looks (and sounds) neat, too, but the exchange there is that it takes even more energy than making a load of winged seeds to actively expel a few seeds from one’s body. Each plant evolves the method of seed dispersal best suited to its environment. If it happens to delight us with showers of whirlygigs or sudden eruptions of seed pods, well, that’s just one more way we’ve benefited from evolution, I’d say. It’s right up there with opposable thumbs in scientists’ minds, I’m sure.

Monsters Mini-Post: On the Various Types of Eyes in the Animal Kingdom, or, The Eyes Have It

Alright, sure, let’s play with that pun on “the ayes have it.” What is it, exactly, that eyes have?

Well, at their most basic, the eyes of animals have three jobs, according to biologists:

1. the detection of light
2. the detection of shadows
3. the transmission of this information about light and dark to motor structures (because it’s one thing to be able to tell where a shadow’s coming from, quite another to be able to move away from it if you think it’s the shadow of a big, bad beast)

In the simplest kind of eye in the animal kingdom, found most often on the various tiny marine creatures we collectively call plankton, the motor structures that act on visual information aren’t muscle cells, like what you’d find in humans and other vertebrates, but cells lined with tiny hairs called cilia, which move the itty bitty organisms through their watery environments like the oars on a ship. The eye that provides these ciliated cells with info is similarly simple (alliteration away!); it’s made up of only two cells, one that receives the light, and another that processes shadows with the help of pigment.

Animal eyes range wildly in complexity, from the basic cup-shaped light and shadow detectors on the top sides of flatworms to the camera-like instruments of focus that we humans tend to roll every time we hear our bosses announce another brilliant idea for efficiency in the workplace.

There are sorts of stops in between, too. Squids and octopuses, for example, possess eyes that have lenses, as human eyes do, but lack the cells called cones that provide the human eye with the ability to perceive color. They can adjust their lenses to focus on objects near or far away but can only visualize those objects in terms of light and dark (though research suggests that octopuses have ways of reacting to color in their environments that have no parallels in human anatomy, which makes them really, really neat).

When it comes to human eyes, it’s been proposed that eyes have other functions besides the three listed above. Humans eyes not only receive information; they apparently also communicate it.

Unlike our relatives the great apes, humans have eyes that are partially white. This white part of our eyes is a structure called the sclera. The primate eye has a sclera, too, but it’s dark in color, frequently brown.

In 2006, anthropologists at the Max Planck Institute for Evolutionary Anthropology ran an experiment in which they had both great apes and human babies watch while researchers looked in one direction, then another, either by moving their heads or moving their eyes. The anthropologists found that the apes were more likely to follow the researchers’ gaze when the researchers moved their heads, while the human tots were more likely to follow when the researchers moved their eyes.

What this suggested is that our eyes evolved as a way of helping us cooperate on certain tasks. With our irises more visible against a white background, the researchers proposed, it would be easier to see where we were looking, so that others could see what caught our attention, too.

And let’s face it: as all the selfies on the Internet demonstrate, we spend a lot of time looking at human faces. In fact, it’s been suggested that eye contact is essential for creating a bond between a human infant and a caregiver, and that human babies spend twice as long staring into their caretakers’ eyes as primate newborns do. Is this behavior influenced by the evolution of the human eye? As always in science, research continues, but there’s a strong possibility that the eyes in this case really do have it.

On White Clover, or, Wow, That Really Isn’t Lucky for Some Animals

Green is good! At least, that’s what we’re taught in our science classes when it comes to plants. Plants with healthy green leaves are busy getting down, doing photosynthesis (which, being a biochemical process, is actually the antithesis of getting down). They’re growing and becoming the mature leafy plant life that eventually animals like cows—or, you know, us—will eat for sustenance.

So why would a plant develop a pattern on its leaves that’s white? Why would a plant include code in its genes for a part of the leaf that doesn’t perform photosynthesis as well?

The photo that inspired this post.

White clover, known scientifically as Trifolium repens, exists throughout Europe, North America, and parts of the Pacific. A lot of people reading this blog have seen it, I bet. Chances are that a few of us as kids plucked it and shouted something like, “I found a lucky clover!” while holding a bunch of it in a small bouquet. Presenting our white clovers in a cluster, we reasoned, made it that much harder to tell that the plants we found growing everywhere really had three leaves instead of the fabled four. How clever we were! (Or, how clever I was, if I’m the only dork here who was sure that that would work.)

Okay, so we/I sucked at getting the adults around us to see what we wanted them to see. Trifolium repens, however, is actually very good at getting the creatures that eat it to notice exactly what’s important.

One widespread form of white clover (which has white flowers, if you were wondering) has leaves that are solidly green, just as you‘d expect from a plant. In contrast, another variety has a pale v-shaped stripe in the center of each leaflet.

That stripe doesn’t exist just for pretties. The variety of white clover with the v-stripe, sometimes known unsurprisingly as “white-striped clover,” produces cyanide inside its cells. It makes just enough of that lethal compound to cause problems for small creatures like snails and slugs that otherwise would eat whatever clover they could find in low-lying areas.

It should come as no shock that the striped white clover is the more common form of clover along low-altitude coastlines like that of Long Island, New York, of the shores of North Carolina, where plant-eating molluscs like to slither. Survival of the fittest, baby! The molluscs in such places have learned that that stripe means danger and so the striped clover lives on. If you want to see the plain form of white clover in abundance, Minnesota is cool. Not as many shell-toting animals in those plains thereas there are by the ocean.

Even if striped white clover is toxic to small animals (and even if any kind of white clover’s ability to grow quickly across a large area of land has led most people label it a weed), it is a green plant, and green is still good:

• Its flowers attract bees, those wonderful pollinators.
• It’s able to deliver the nitrogen that other plants need to grow into the soil, making it good for crop rotation (provided it doesn’t take over the land).
• It’s bovine approved—white clover often gets added to livestock feed to improve its quality.

In other words, one animal’s poison is another one’s lunch. I think that’s how the quote goes, anyway.