More Than Just Ball Rollers —An Investigation Into Risky Roly-Polies
Roly-poly season is among us — if you live in a wet, temperate spring (such as Pittsburgh, Pennsylvania).
You know what I mean by roly-poly, right? Also known as pill bugs, woodlouse, or more formally, Armadillidium vulgare. Those beetle-like creatures (they’re actually crustaceans) that look like little armadillos and instantly curl into a little ball when you touch them.
I noticed one on the patio the other day and instantly felt gleeful and nostalgic, thinking about how excited I got seeing them roll into a ball when I was a kid.
Roly-Polies/Pillbugs: The Background
Roly-polies are originally from the Mediterranean region, but now exist in every continent besides Antarctica, mainly in temperate climates. Roly-polies vary in size, but are generally about 1.5 to 2 centimeters in length.
As mentioned earlier, they are not insects — rather they are terrestrial crustaceans. They are, in fact, the only crustaceans that live entirely on land. Roly-polies have a hard outer shell and seven pairs of legs. They even have gills, so it’s important that they stay near moist areas. When threatened, roly-polies roll into a ball to protect its softer underparts, in a process known as “conglobation”. This process also helps protect
Besides conglobation, roly-polies have other characteristics that make them a pretty interesting animal. For example, roly-polies play an important role in improving soil quality because they are detritivores, meaning they feed mainly on decaying organic matter, such as rotting leaves. By feeding on organic matter, roly-polies help increase the bioavailability of nutrients in the soil, contributing to soil quality.
Also, roly-polies eat their own poop and . Roly-polies eat their own poop to . The reason they don’t urinate is because they have a high tolerance to ammonia, and so they can instead release ammonia gas through their exoskeletons, resulting in lower water loss.
Another interesting fact: roly-polies can get infected with bacteria and viruses with some intriguing consequences. One type of bacteria, Wolbachia, can cause roly-polies . A family of viruses called Iridoviruses can cause e.
Roly-Polies Are Also Great Models For Studying Personality and Behavior
Since roly-polies roll into a ball when they’re feeling threatened, this response is considered both predictable and easily measurable, making roly-polies/pill bugs a great model for studying personality behavior.
In a, researchers exposed roly-polies to environments that the roly-polies were familiar with and also to environments that they were unfamiliar with. The researchers then measured the risk taking behavior of the roly-polies, which they defined as the time it took for them to resume activity after rolling into a ball. The roly-polies were induced into rolling into a ball through simulated predator attacks (mainly, the researchers gently squeezing the roly-polies).
The study found that roly-polies differed among each other in their average risk taking behavior and that they became less risky as they became more familiar with the environment. Kind of the opposite of what I would’ve expected, but this behavior in familiar versus unfamiliar environments was consistent with several other animal studies ().
Roly-polies infected with the bacteria Wolbachia had lower risk-taking behavior compared to uninfected roly-polies. Also, being female or larger in size was related to being less risky as time went on. These results showed that roly-poly behaviors are affected by many factors, including both intrinsic and environmental factors.
Microplastics Are Making Roly-Polies Act Riskier
In a more , Horváth and colleagues assessed how the ingestion of microplastics by roly-polies/pill bugs could affect their behavior. The study defined microplastics as synthetic polymer particles less than 5mm, originating from larger plastic debris (secondary microplastics) or manufactured at that size for specific applications (primary microplastics).
The researchers conducted controlled laboratory experiments where roly -polies were fed or not fed microplastics in their food for 6 weeks. They then observed and recorded the roly-polies’ behaviors in environments that simulated natural conditions, focusing on activities that indicate risk-taking, such as exposure to open spaces versus staying in covered areas.
The results showed that the roly-polies that had consumed microplastics had increased risk-taking behaviors compared to those that did not ingest microplastics. Specifically, they were more likely to venture into open areas, which could expose them to predators and other environmental hazards.
The Implications: Why Roly-Polies Probably Shouldn’t Act So Risky
The experiment showed that the roly-polies that ingested microplastics behaved with less caution. This is potentially concerning, as participating in more risky behaviors may affect their survival rates. As the roly-polies are major decomposers, they play an important role in breaking down plant matter and increasing nutrient bioavailability in the soil. Hence, their behavior changes could have broader ecological implications as well.
