Tag Archives: bioluminescence

Episode 392: Moon Jellyfish, Kung Fu Mantis, and Octocorals

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Thanks to Kari and Joel for their suggestions this week! You can find Kari Lavelle’s excellent book Butt or Face? Volume 2: Revenge of the Butts at any bookstore.

Our Kickstarter for some enamel pins goes live in just over a week if you’re interested!

Further reading:

Jellyfish size might influence their nutritional value

History of Taiji Mantis

Glowing octocorals have been around for at least 540 million years

The moon jellyfish [photo by Alexander Vasenin – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=32753304]:

A Chinese mantis [photo by Ashley Bradford, taken from this site]:

Also a Chinese mantis:

A type of octocoral:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

It’s finally Invertebrate August! We have some great episodes coming up this month, so let’s get started. Thanks to Kari and Joel for their suggestions this week!

First, we’ll start with an invertebrate from Kari Lavelle’s latest book, Butt or Face? Volume 2: Revenge of the Butts! It’s a sequel to the hilarious and really interesting book we talked about last summer. Kari kindly sent me a copy of the book and it’s just as good as the first one. Don’t worry, I won’t spoil the answer of whether the picture in the book is of an animal’s butt or face, but let’s talk about the moon jellyfish.

We’ve talked about jellyfish in several previous episodes, most recently in episode 343. Moon jellyfish is the term for jellies in the genus Aurelia, all of which look so identical that it takes close study by an expert, or a genetic test, to determine which species is which. We’re going to talk about a specific species in this episode, Aurelia aurita, but most of what we’ll learn about it also applies to the other moon jelly species.

Aurelia aurita lives in temperate, shallow water and is often found in harbors and close to shore. It’s mostly transparent and can grow up to 16 inches across, or 40 cm, although most are smaller. It’s sometimes called the saucer jelly because when its bell is open, it’s shaped sort of like a saucer or shallow bowl, if the bowl was upside down in the water with pinkish-white internal organs inside and short stinging tentacles. That’s most bowls, I think.

Unlike a lot of jellyfish, the moon jelly doesn’t have long tentacles that hang down from the middle of the bell. Instead, its tentacles are short and thin and line the edges of the bell. There are hundreds of them, but while the tentacles do have stinging cells, they’re not very strong. If you were to pet a moon jelly, you probably wouldn’t even feel the stings but you’d probably get sticky digestive mucus on your hands from the tentacles. The mucus is sticky to trap tiny pieces of food, which can include everything from fish eggs and various types of larvae to microscopic animals called diatoms and rotifers.

The moon jellyfish can survive in water with low oxygen, and in fact it prefers low oxygen water. Since most larger marine animals that live near the surface need a lot of oxygen to survive, the moon jelly can safely find its tiny food in low-oxygen areas without worrying too much about predators. Actually the moon jellyfish doesn’t worry about much of anything, because like other jellies, technically it doesn’t have a brain, just a nerve net.

Speaking of predators, for a long time scientists have wondered why anything bothers to eat jellies. They’re mostly water, which makes them easy for other animals to digest, but they contain almost no nutritional value. A study published in March 2023 determined that the bigger the jellyfish is, the more fatty acids its body contains, and fatty acids are an important nutrient. The main difference between a little jelly and a big jelly (besides size) is what they eat, so scientists think the bigger jellies are eating prey that contain more fatty acids, which slowly accumulate in the jelly’s body too.

Next, Joel sent a bunch of excellent suggestions for invertebrates, so many good ones I had trouble choosing which one to put in this episode. I chose the kung fu mantis because I love the Kung Fu Panda movies and think Mantis is an awesome character who is not appreciated enough.

Everyone loves praying mantises and we’ve talked about various species in different episodes, most recently episode 375. The one we’re talking about today is specifically called the Chinese mantis, Tenodera sinensis, which is native to Asia but which is invasive in parts of North America. It grows over 4 inches long, or about 11 cm, and is brown and green in color. It has a yellow spot between its raptorial arms, which as you can guess from the “raptor” part of that word are the arms with the big spikes that help it catch and kill its prey.

The reason this mantis is also called the kung fu mantis is because its ferocity and grace when hunting inspired a style of martial arts in China hundreds of years ago. The story goes that a great hero called Wang Lang was defeated in a duel, and afterwards set himself to study and train harder. One day he noticed a bird trying to catch a praying mantis, but the mantis was so skilled in defending itself against a much larger opponent that the bird eventually gave up and flew away. Wang Lang was inspired to incorporate the mantis’s movements into kung fu, and afterwards he never lost a duel.

Like other mantises, the Chinese mantis will eat pretty much anything it can catch. That’s mostly insects and spiders, but occasionally it will eat frogs and other amphibians, lizards and other reptiles, and occasionally even small birds. It’s a good insect to have around the garden because it eats so many garden pests, but it also eats bees and butterflies, which isn’t so good for the gardener. The Chinese mantis also eats other mantises, which is a problem in North America where it will kill and eat the native mantis species. But because the Chinese mantis is easy to keep in captivity, if you order mantises to release in your garden in the United States, as a natural pest control, there’s a good chance that the species is actually the Chinese mantis. The native Carolina mantis looks very similar but is smaller, only about 2.5 inches long, or 6 cm.

The Chinese mantis also eats other Chinese mantises. You may have heard about how the praying mantis female will bite the male’s head right off after or even while they’re in the process of mating, and then she’ll just eat him up for a nice big meal to help her develop her eggs. This is actually something that happens, although not always. In the case of the Chinese mantis, scientific observations have found that the female eats the male about half the time.

Let’s finish with a type of coral you may not have heard of, octocoral, also called soft coral. We’ve mentioned corals lots of times in various episodes but we haven’t really discussed them in detail. When most people think of coral they think of stony corals that make up coral reefs. Most corals are colonial animals, meaning each individual polyp grows together in a group, and stony coral polyps form a type of exoskeleton or shell made of calcium carbonate to protect its soft body. The polyps have small tentacles that they extend into the water to catch plankton and other particles of food, although some species are larger and can even grab little fish. The tentacles contain stinging cells called nematocysts that can stun or even kill small animals. As the colony grows, with old polyps dying and young polyps attaching to the hard skeletons left behind, the reef gets larger and larger as the years pass.

Not all stony corals live in shallow warm water and build reefs. Some live in cold water and deeper water, and there are even deep-sea corals, and these types of coral don’t build reefs. Octocorals don’t build reefs and are found in both shallow and deep water, and they don’t form hard skeletons.

Instead, the polyps of octocoral form a soft tissue full of tiny channels that allow water through. Octocorals are colonial, so the tissue of each polyp blurps together with those of all the other polyps around it. Some species of octocoral secrete little pieces of harder material to help the tissue keep its shape, but most species are still overall quite soft. It’s strong, though, and the tiny channels through it allow water to carry nutrients to all the polyps.

The octocoral gets its name because it has exactly eight tentacles, although the tentacles are feathery in appearance with lots of little branches growing off the main tentacle. This allows it to catch more tiny food. Some octocorals have long, elaborate tentacles, which has earned them the names sea fans and sea pens, from the old-timey days when pens were made from big feathers.

Corals in general appear in the fossil record for about half a billion years, with stony corals more likely to preserve for obvious reasons. Many species of octocoral exhibit bioluminescence, and that leads us to a recent study, published in April 2024.

Until this new study, scientists estimated that the first bioluminescent creatures lived around 250 million years ago. Bioluminescence has evolved separately over 100 times, though, and is found today in animals as different as fungus and fish. For the new study, scientists analyzed the genetics of 185 octocoral species to see how they were related, and then compared their findings with fossil corals to learn more about when the species split from their common ancestors. That gave them a good idea of when octocorals might have evolved originally and hinted at which ancestors were bioluminescent. They estimated that the first octocoral evolved around 540 million years ago and was already bioluminescent!

The scientists who worked on the study suggest that bioluminescence may have developed originally as a byproduct of other chemical reactions, but it was useful to the animal by possibly attracting food or other octocorals. Bioluminescence is common in marine animals these days, especially in deep-sea animals, so it’s possible that the ocean half a billion years ago was filled with lights from octocorals and many other organisms.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us for as little as one dollar a month and get monthly bonus episodes.

Thanks for listening!

Episode 180: Synchronous Fireflies

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Thanks to Adam for the great suggestion of synchronous fireflies! Let’s learn about lightning bugs (or fireflies) in general, and in particular the famous synchronous fireflies!

Further reading:

How Fireflies Glow and What Signals They’re Sending

Further watching:

Tennessee Fireflies

Synchronizing Fireflies in Thailand (it shows an experiment to encourage the fireflies to start blinking by the use of LEDs)

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we’re going to learn about a bioluminescent insect, the firefly, also called the lightning bug, but we’ll especially learn about a specific type of various species called synchronous fireflies! This is a suggestion from Adam, so thank you, Adam!

Fireflies are beetles and they’re common throughout much of the world. I actually call them lightning bugs, but firefly is faster to say so I’m going to use that term in this episode. They’re most common in temperate and tropical areas, especially around places with a lot of water and plant cover, like marshes and wooded streams. This is because the firefly spends most of its life as a larva, and it needs to be able to hide from predators and also find the tiny insects, snails and slugs, worms, and other small prey that it eats. Adults of some species don’t eat at all and may not even have mouths, while adults of other species may eat nectar, pollen, or other insects.

There are probably two thousand species of firefly, with more being discovered all the time. While they vary a lot, all of them emit light in one way or another. We’ll talk about how they produce the light in a minute, but first let’s talk about why they light up. In many species, the larvae can light up and do so to let predators know they taste bad. The larvae are usually called glowworms, although that name is also applied to other animals.

Some firefly species don’t light up at all as adults, but many species use their lights to find a mate. Every species has a distinct flash pattern. In some species, the female can’t fly but will sit on the ground or in foliage and watch for her species’ flash pattern from males flying around. When she sees a male she likes, often one whose light is brightest, she signals him by flashing back. Sometimes a pair will flash back and forth for hours, sometimes just minutes, but eventually the male will find the female and they will mate.

As a result, the firefly is sensitive to light pollution, because it needs to see the flashing of potential mates. If there’s too much light from buildings and street lamps, fireflies can’t find each other. They’re also sensitive to many other factors, so if you have a lot of fireflies where you live, you can be proud to live in a healthy ecosystem. But overall, the number of fireflies are in decline all over the world due to habitat loss and pollution of various kinds.

So how does a firefly light up? It’s a chemical reaction that happens in the lower abdomen in a special organ. The organ contains a chemical called luciferin [loo-SIF-er-in] and an enzyme called luciferase [loo-SIF-er-ace], both of which are found in many insects that glow, along with some other chemicals like magnesium. The firefly controls when it flashes by adding oxygen to its light-producing organ, since oxygen reacts with the chemicals to produce light.

Female fireflies in the genus Photinus, which are common in North America and other areas, can’t fly and instead look for potential mates to fly by. When a male sees a female’s answering flash, he lands near her. But sometimes when the male lands, he’s greeted not by a female Photinus but by a female Photuris firefly. Photuris females often mimic the flash patterns of Photinus, and they do so to lure the males close so they can EAT THEM. Photuris is sometimes called the femme fatale firefly as a result. Some species of Photuris will also mimic the flash patterns of other firefly species, so they don’t specifically pick on Photinus. Also, these names are way too similar. Photuris will even grab and eat fireflies that are caught in spiderwebs, stealing from the spider. I like to imagine these femme fatale fireflies with tiny guns and slinky 1950s-era dresses.

But the really interesting thing is that these femme fatale fireflies aren’t just hungry. They belong to species that can’t manufacture the toxic compounds that other fireflies do. After a female Photuris has mated, she needs this compound to protect her eggs when she lays them, so she gets it by eating fireflies that do produce the compound.

Fireflies vary in size, but they’re generally quite small, with the biggest only about an inch long, or 2.5 cm. They’re usually brown or black, sometimes with orange, red, or yellow markings on the head and yellow streaks on the wing covers. They also have a weird smell, which is probably related to this toxic compound. It’s a type of steroid that’s chemically similar to the toxins excreted by some poisonous toads. In one fantastic article I found online, which I link to in the show notes, the writer says, “A colleague of mine once put a firefly in his mouth—and his mouth went numb for an hour!” In other words, don’t eat fireflies even if you’re a frog or a bird.

In many areas, larval fireflies hibernate during the winter, in underground burrows or under tree bark. Once a larva pupates and transforms into an adult, it only lives a matter of weeks. It mates, lays eggs, and dies.

There is an exception, of course. The winter firefly lives in much of North America and actually overwinters as an adult. It lives in tree bark in the winter, coming out in early spring. But the adult winter firefly doesn’t light up. It’s not even nocturnal like most other species. It comes out during the day and the male finds a mate by following the trail of pheromones released by the female. It eats tree sap and is especially attracted to sap buckets when people are tapping maple trees to make maple syrup, which is why it’s also sometimes called the sap bucket beetle. It mates and lays its eggs in spring, then dies. Larvae pupate in late summer so that new adults have several months to build up energy reserves to get them through the winter.

Synchronous fireflies are native to Southeast Asia and the eastern United States, from Georgia to Pennsylvania. There are several famous sites in the United States for synchronous fireflies, including one that’s very close to me, at Elkmont in the Great Smoky Mountains National Park. There are 19 species of firefly in the park, but only one, Photinus carolinus, flashes synchronously. So many people want to see the display that the park has to have a lottery to see who gets tickets. I’ve never been to see the synchronous fireflies, but I have seen synchronous fireflies, at a spot only a five-minute drive from my house.

WHAT?, you may be thinking, if you know anything about synchronous fireflies. There are only like three spots in the United States where these fireflies live! But this actually isn’t the case. In 2015 another species was discovered in East Tennessee, specifically in the Oak Ridge Wildlife Management Area. I remember reading an article about it and contacting the scientist quoted in the article, because I already knew of some synchronous fireflies near my house. No one else seemed to know about them but me.

I looked for the email I got in response, but unfortunately I must have deleted it at some point. This was way before I’d started the podcast so I didn’t think I’d ever need to refer to it. All I remember is that the scientist’s last name was also Shaw and that he said he’s sure there are lots of small pockets of the synchronous fireflies in East Tennessee and surrounding areas, and that they were a different species from the ones in the Smokies, with a different flashing pattern.

And indeed, there are two species of synchronous fireflies in the United States, Photinus carolinus and Photuris frontalis. Photuris is the one I’ve seen. But there’s also a third species of synchronous fireflies in the United States, but it’s only found in Arizona. The species is Photinus knulli, but it’s rare and doesn’t congregate in huge numbers.

The synchronous fireflies found in mangrove forests and other forested areas in southeast Asia are much more common than the species found in the United States, and flash year-round instead of for only a few weeks in summer. I have a couple of links to synchronous fireflies in the show notes, one of them in Tennessee and one in Thailand. The Thailand video is better since you get a better idea of how in synch the fireflies are. In that case, as the video shows, the fireflies were encouraged to start their light show by an experiment with computer-controlled LEDs hidden in a few trees.

So the videos are good, but what do synchronous fireflies really look like when you’re there in person? I mean, it’s easy to say that all the fireflies light up at once and it’s beautiful, but I’ve seen them and this doesn’t even start to explain how amazing it looks. The videos are accurate but let me try to describe my experience.

The ones I’ve seen live in a very small part of the local watershed, on the hillside above a stream called Clear Creek. They only live on one side of the stream, which fortunately is the side where there’s a hiking trail. It’s amazing because you can look across the creek and see just ordinary fireflies flashing, then turn around and see a spectacular lightshow. And even though it’s literally a few minutes’ walk from a little parking lot, I don’t think anyone but me has ever noticed.

They only flash in mid-June when the days are long, so you have to be out late to see them, around 10pm or later. The first time I saw them I was out hiking and went farther than I’d intended, so it was dark when I was approaching the parking lot.

In East Tennessee on a summer evening, it’s dark under the trees but the sky still holds a little light, so that when you look up through the tree canopy you see patches of dark blue. On this particular stretch of trail, it’s dangerous to walk too fast because there are lots of roots and rocks that you can trip over in the dark. So imagine you’re walking along with just enough light from the sky to tell where the trail is. Clear Creek is to your left, broad and shallow here. You can hear it gurgling over rocks. To your right, the ground rises steeply—not too steep to climb if you wanted to, but too steep to bother.

It’s a summer evening, so of course there are fireflies. You don’t pay any attention until you notice something unusual to your right, on the hillside beneath the trees.

That’s funny, three or four fireflies flashed at exactly the same time. But now that your attention is on the hillside, you see another flash as dozens of fireflies light up at the same time. And a few seconds later, when it happens again, you realize that it’s ALL the fireflies on the entire slope—hundreds of them!

At a distance, the flashing looks like a gold-tinted glitter of light, not a glow. Hundreds of tiny glittering lights blink on and then immediately off, so that the entire hillside looks like it’s covered with tiny electric bulbs winking on and off. The flashes come in groups, two or three flashes in a row over the course of several seconds, then a pause, then more flashes. The fireflies on one side of the hill are slightly out of synch with those on the other side of the hill so that the flashing seems to travel in a wave across the hillside. It’s so beautiful you can hardly believe what you’re seeing. It doesn’t even seem real.

One thing I’ve noticed, after being lucky enough to witness this amazing sight several summers in a row, is that the flashing doesn’t fully synchronize until it’s really dark. If I get there too early, I can see the fireflies are trying, but they aren’t quite in time yet. It has to be dark enough for them to really be able to see each other.

So why do some fireflies synchronize their flashing while most don’t? Researchers aren’t sure, but the best guess is that by flashing all together, it’s easier for females to compare males and choose which male they want to mate with. The males may also be trying to keep other males from flashing before they do, which means they eventually all synch up.

It really is an amazing sight. If you’re ever going to be in East Tennessee in June, let me know and I’ll take you out to see my fireflies, or you can sign up to see the really big displays in the Smokies or other areas. Until then, hopefully my description will help you imagine it.

This is what a firefly sounds like. HA, fooled you, they don’t make any noise at all.

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave a rating and review on Apple Podcasts or wherever you listen to podcasts. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!