This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Everyone knows the ocean is full of plankton. How else would whales eat? What you may not know is how slippery and underhanded said plankton can be. Really, it deserves to get eaten by those whales.
Because as it turns out, according to a 2017 study, about half of the microscopic plankton traditionally thought of as animal-like – that is, completely dependent on eating things to survive – have a dirty little secret: they also have the option of making their own food, but only after capturing an innocent green microbe and … well, it’s not nice.
They may engulf and enslave them.
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Or they my simply eat them and steal their chloroplasts.
The perpetrators are complex single-celled organisms that are fascinating to watch. Here is Dinophysis sucking the chloroplasts out of a hapless victim.
And here is Strombidium, doing its best impression of a winged canopic jar or flying heart. There appear to be lots of orange-ish chloroplasts stuffed inside. It periodically inflates and deflates some sort of organelle (a contractile vacuole?), giving he impression of breathing.
This Mesodinium is a bowling pin-shaped creature whose cilia appear to rotate.
Here's Noctiluca scintillans, a protist that takes photosynthetic hostages but also lights up when disturbed, giving it the nickname "sea sparkle". This individual is lazily waving a flagellum, whose usual function is to stuff food inside and sweep waste out. The baggy body appears to be empty of involuntary house guests.
Although completely unrelated to the topic of this post, add some serious joy to your day with this video of Nocitluca’s bioluminescent capabilities.
Upending previous assumptions that such plankton are oddballs, the 2017 analysis of oceanographic encounters with these organisms revealed that they are “ubiquitous and abundant”.
The catch-and-enslave type is found most often in the open ocean where food and victims are scarce. Better to ensure a steady supply of eggs than to fry the chicken straight away when you're not sure when you'll find your next bird.
The strip-and-consume type is more abundant in the marine equivalent of a 24-hour KFC, such as coastal and upwelling zones with nutrient-rich waters. They need a conveyer belt of prey to keep them well stocked in chloroplasts and essential nutrients.
The authors of this study heartily encouraged the creators of ocean models that do not take this rather significant new finding of unsuspected photosynthesis into account to, you know, fix them.
Reference
Leles, S. G., Aditee Mitra, Kevin J. Flynn, Diane K. Stoecker, Per Juel Hansen, Albert Calbet, George B. McManus et al. "Oceanic protists with different forms of acquired phototrophy display contrasting biogeographies and abundance." Proceedings of the Royal Society B: Biological Sciences 284, no. 1860 (2017): 20170664.