#actinobolina

"What you're looking at right now might not immediately stand out. You've got a sea of green organisms, and then in the middle is a clear-ish oval. And that oval is what we're going to talk about today. Because over the course of three years, James' many, many excursions into different watery sources have turned up only three of them. And as rare as the species is, we think the footage he's taken might be even harder to come by."

Journey to the Microcosmos- Actinobolina: A Tiny Predatory Porcupine

Images Originally Captured by Jam's Germs

cc: "Organisms pass and pass, but nothing tempts the hunter until a specific prey comes along: the unsuspecting ciliate called Halteria. The Actinobolina stabs it with a tentacle, which is loaded with a toxicyst at the end to immobilize the prey. And then the tentacle draws the food in, to its inevitable end. The acctinobolina digests its mean, but as Calkin himself said, it is insatiable. So it retracts its tentacles and leaves, seeking out a new spot to stretch out and ensnare its next meal."

Journey to the Microcosmos- Actinobolina: A Tiny Predatory Porcupine

"And here it is again, catching another Halteria with its tentacles. Using the word "tentacle" makes the actinobolina sound like an octopus. But watching the hunt in action, it looks more like a porcupine with its quills fully extended. But a porcupine that uses its quills to skewer meals instead of protect itself, and then it retracts the quills so it can rush on to the next spot. We might be testing the limits of our comparisons right now. But that's okay. According to our calculations, we've got about a year until our next actinobolina. So when that rolls around, we'll be ready with some new ones."

Journey to the Microcosmos- Actinobolina: A Tiny Predatory Porcupine

"We mentioned that [James] found only three actinobolina in three years. This is the third one, found the morning after reading Calkin's paper. When James observed his first actinobolina, he didn't yet know how rare they were. And his second actinobolina died quickly, likely due to some kind of temperature shock. So with this third member of the species, James made sure to take extra care to keep it alive and follow it around so he could observe as much as possible."

Journey to the Microcosmos- Actinobolina: A Tiny Predatory Porcupine

"Part of the fun of reading these old papers is getting to see how well these observations made by scientists over a century ago match up to what we can see now. It's like exchanging lettes with the past, and out little actinobolina is the courier. And it's all even more exciting for us in this case, because as far as we can tell, not many people have gotten footage of the actinobolina in the midst of a hunt. But while Calkins may not have had the technology we have today to capture what he saw, he did provide detailed descriptions that line up nicely, starting with the surprisingly particular tastes of the actinobolina."

"And when it's zipping around the microcosmos, the actinobolina's cilia seem to have more of a vibration to them than the usual wave-like stroke associated with cilia. In fact, they kind of resemble flagella more than cilia. But we don't know much more about why or how this movement works. In his description of actinobolina, Calkins writes, "It is when the animal is quiet that it takes in food. It remains for hours, sometimes, without giving a sign of feeding, but the tentacles are stretched out to their greatest length and it appears merely waiting for something to come." We don't know if he meant for it to sound as ominous as it does, but it certainly feels appropriate for a tentacle predator."

Journey to the Microcosmos- Actinobolina: A Tiny Predatory Porcupine

"Now, what makes the actinobolina so notable are the tentacles lining its body. They can be a little difficult to make out from far away, but you can see the faint lines of them surrounding the body. With great magnification though, you can start to see the bundles of cilia and tentacles a bit better. The tentacles can reach to around 2.5 yimes the lenght of the organism's diameter when fully outstretched. But even more cool than how far the tentacles go out is how far in they go-like when the actinobolina needs to move around and doesn't want some cumbersome extensions getting in the way."

Journey to the Microcosmos- Actinobolina: A Tiny Predatory Porcupine

"First, let's talk about the tentacles. This isn't our first tentacle sighting in the microcosmos. We've seen them before on actinobolina, made through a similar assembly of microtubules--though the actinobolina's extensions look a lot spikier next to the dotted end of the suctorian's tentacles. Plus, unlike the spikes that radiate around the entirety of the actinobolina's body, many suctorian species keep their tentacles bundled together."

Journey to the Microcosmos- Suctorians: The Ugly Duckling of Ciliates