Jellyfish do not have bones, a brain or a heart, but what they do have is incredible swimming skills, finds new research.
Jellyfish can detect the direction of ocean currents and swim strongly against them, according to the study, which is published in the latest issue of the journal Current Biology. The research adds to the growing body of evidence that creatures without brains, such as carnivorous plants, can still be clever.
“Detecting ocean currents without fixed visual reference points is thought to be close to impossible and is not seen, for example, in lots of migrating vertebrates including birds and turtles,” co-author Graeme Hays of Deakin University in Australia said in a press release.
“Jellyfish are not just bags of jelly drifting passively in the oceans,” he added. “They are incredibly advanced in their orientation abilities.”
The following video shows how jellyfish swim. The speed of the undulations can go much faster than this, depending on the ocean currents.
Hays and his colleague Sabrina Fossette of the Swansea Lab for Animal Movement came to that conclusion after using GPS loggers to track the movements of free ranging barrel jellyfish. The researchers also set out GPS-tracked floats to record ocean current activity.
The data from those devices showed that jellyfish sometimes actively swim against currents in response to drift. In short, they seem to control their destinations, as opposed to just passively drifting around their ocean habitats.
Jellyfish can be pesky creatures, as they sometime form “blooms,” which are essentially swarms of jellyfish that suddenly appear at ocean surfaces. The new research helps to explain how these blooms form, with hundreds to millions of individuals swimming to certain locations and staying there for up to several months.
Now the mystery is: without a brain, how are jellyfish so "smart?"
Fossette and Hays theorize that the animals detect ocean current shear across their body surface, or they may detect Earth’s magnetic field or infrasound, both of which can be used for orientation.
Knowing where jellyfish are, and where they’re going, is helpful info for us and other animals. Jellyfish serve as important prey for many species, such as leatherback sea turtles. In their case, finding a jellyfish is great. Fishermen and human beachgoers aren’t so thrilled, given that jellyfish can clog fishing nets and sting bare feet and legs.
It's amazing, though, how jellyfish swim with purpose, given that they have no visual cues (or eyes, for that matter) and spend much of their time surrounded by seemingly endless water.
"Now that we have shown this remarkable behavior by one species, we need to see how broadly it applies to other species of jellyfish," Hays said. "This will allow improved management of jellyfish blooms."
Photo: A Pacific sea nettle jellyfish. Credit: Wikimedia Commons