Even the most ideal marine organisms tend to be individualistic

At first glance, the star of the recent study may not seem particularly impressive: just a few centimetres long, Platynereis dumerilii is a species of polychaete worm that can be found in temperate to tropical coastal waters around the globe; if your goal is to find notable animal personalities, there are certainly better-suited candidates. But that was not the main goal of the study, which experts from the AWI, the Max Perutz Labs in Vienna, the Universities of Vienna and Oldenburg, and the Katholieke Universiteit Leuven in Belgium contributed to. Initially, the researchers were drawn to the internal clocks that regulate daily rhythms in countless organisms.

“Biological timing is crucial at a range of levels,” explains Kristin Tessmar-Raible, a biologist at the AWI. “The ecological ties between species depend just as much on it as they do on biochemical processes at the cellular level.” But how do organisms’ internal clocks react when humans heat the climate or use artificial light to turn night into day? “In terms of marine organisms, we still know little or nothing,” says Sören Häfker, the study’s lead author. In this regard, rhythms are especially important in their lives: temperature, available light and food, and various other factors change over the course of the day, and the organisms must respond accordingly. They adapt their behaviour, metabolism, and gene expression to these external rhythms.

Then again, it remains unclear whether they will be equally successful at doing so in the future. And when their internal clocks no longer match their environment, it could become a matter of survival. “As such, we need a much better understanding of how the rhythms of the oceans are changing and what this could mean for individual species and populations,” the biologist stresses — meaning there could be a wealth of reasons to take a closer look at the daily behaviour of Platynereis dumerilii. In fact, for chronobiology, which focuses on organisms’ internal clocks, this distant relative of the earthworm has become one of the most valuable model species.

In past experiments, the team experiments, the researchers had noticed how the worms had moderately different daily rhythms. Among humans, it is a well-known phenomenon: early birds do not always become night owls, and vice versa. But what about in marine polychaete worms? Are their behavioural differences just random variations or do they also have a personal tact? To find out, the team systematically observed the worms’ daily activities when there was a new moon. What they observed: some individuals became active at exactly the same time every night. In turn, others appeared to be arrhythmic “couch potatoes” that were only occasionally active — plus, there were various “shades of grey” between these two extremes. When the same worms were observed again several weeks later, their behaviour remained largely unchanged: once a couch potato, always a couch potato. “We were very surprised to see how reproducible the individual behavioural rhythms were,” says Tessmar-Raible. “This shows us that even worms have small, rhythmic personalities, so to speak.”

Extra individuality=extra resiliency

To gain further insights into these behavioural differences, the team systematically compared the genetic activity in the heads of worms prone to particularly rhythmic and arrhythmic behaviour. Surprisingly, they found that the daily internal clock worked perfectly well in all specimens, even the arrhythmic “couch potatoes,” and that the number of genes with rhythmic activity was nearly as high as in the “punctual” worms. The large number of solutions they make use of could even give the worms an evolutionary advantage, as the experts surmise. After all, they live in a coastal environment with highly variable conditions; as such, lifestyle A could be the ideal choice for a given location, whereas not far away, lifestyle B could be a better fit. Moreover, this kind of individuality could even make them more resilient to significant anthropogenic changes — in a changing world, this variation increases the chances that at least some worms will be able to cope with their current conditions.

But the look doesn’t just provide recent insights into marine rhythms; it additionally underscores the proven fact that the processes at work within a given organism aren’t basically reflected in its behaviour: even among the sofa potato worms, the genetic direct follows a every day rhythm, even though it be no longer externally recognisable. And that is the reason likely correct no longer only for worms, but for human beings as wisely. “That is why such findings are additionally piquant for fields handle chronomedicine,” says Tessmar-Raible.

In most recent years, there own been intensified and a success efforts to own sufferers’ particular person every day rhythms in thoughts within the context of treating them. But, honest as with the worms seen, they encompass a mountainous preference of parts, ranging from behaviour to genetic direct, which is able to react in a different way to medicines and the timing of once they’re administered. Accordingly, especially in phrases of human beings, it could per chance per chance be important for chronomedical analyses to take into memoir plenty of assorted ranges — if even worms would be so individualistic, our species is probably going no exception.