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,