The first feeding study of tropical Australia’s Irukandji box jellyfish has found that they actively fish. They attract larval fish by twitching their extended tentacles, highlighting their nematocyst clusters (stinging structures) and using them as lures. It’s an impressive feat by any standards, but particularly so for an animal that doesn’t have a defined brain.
“They’re not opportunistically grazing — they’re deliberately fishing. They’re targeting and catching fish that are at times as big as they are, and are far more complex animals. This is a really neat animal that is displaying a surprisingly complex prey capture strategy.”
The researchers were able to catch Carukia barnesi in the act by filming them through a full day and night cycle, using infrared-sensitive equipment to record behavior in times of complete darkness.
Abstract:Adult Carukia barnesi medusae feed predominantly on larval fish; however, their mode of prey capture seems more complex than previously described. Our findings revealed that during light conditions, this species extends its tentacles and ‘twitches’ them frequently. This highlights the lure-like nematocyst clusters in the water column, which actively attract larval fish that are consequently stung and consumed. This fishing behavior was not observed during dark conditions, presumably to reduce energy expenditure when they are not luring visually oriented prey. We found that larger medusae have longer tentacles; however, the spacing between the nematocyst clusters is not dependent on size, suggesting that the spacing of the nematocyst clusters is important for prey capture. Additionally, larger specimens twitch their tentacles more frequently than small specimens, which correlate with their recent ontogenetic prey shift from plankton to larval fish. These results indicate that adult medusae of C. barnesi are not opportunistically grazing in the water column, but instead utilize sophisticated prey capture techniques to specifically target larval fish. –
Robert Courtney, Nik Sachlikidis, Rhondda Jones, Jamie Seymour. Prey Capture Ecology of the Cubozoan Carukia barnesi. PLOS ONE, 2015; 10 (5): e0124256 DOI: 10.1371/journal.pone.0124256
See also: Animal mind
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4 Replies to “Brainless jellyfish shows purpose?”
What do you know for absolutely no reason whatsoever there is purpose…..
of related note:
Jellyfish Sense Their Environment for Controlled Migration – January 27, 2015
Excerpt: Jellyfish are not exactly the quarterbacks (or leatherbacks) of the animal kingdom, but they have surprised researchers with their ability to swim against the tide, just like baby leatherback turtles do. Scientists even think they may be able to sense the earth’s magnetic field, as do turtles, salmon, birds, and other long-distance migrators.,,,
“Jellyfish are not just bags of jelly drifting passively in the oceans,” he adds. “They are incredibly advanced in their orientation abilities.”
Did Neurons Evolve Twice? – The comb jelly, a primitive marine creature, is forcing scientists to rethink how animals got their start. – March 25, 2015
Excerpt: According to traditional evolutionary biology, neurons evolved just once, hundreds of millions of years ago, likely after sea sponges branched off the evolutionary tree. But Moroz thinks it happened twice — once in ancestors of comb jellies, which split off at around the same time as sea sponges, and once in the animals that gave rise to jellyfish and all subsequent animals, including us. He cites as evidence the fact that comb jellies have a relatively alien neural system, employing different chemicals and architecture from our own. “When we look at the genome and other information, we see not only different grammar but a different alphabet,” Moroz said.
Amazing Jellies – video
The weird, wonderful world of bioluminescence – Edith Widder – video
Instant Body Plans: The Case of Jellyfish – July 26, 2013
Excerpt: Cubomedusae (box jellyfish) are particularly interesting. They have eyes that are almost human-like! “As the name depicts, Cubozoans have a squarish shape with four tentacles and four rhopalia. Each rhopalium contains six eyes of four different types, two of which (the upper lens eye and the lower lens eye) are highly developed image-forming eyes with cornea, pupil, lens, and retina, much like our own….”
“The earliest widely accepted animal fossils are rather modern-looking cnidarians, possibly from around 580 million years ago, although fossils from the Doushantuo Formation can only be dated approximately.” So it’s not clear that the dates are right, but even if they precede the main (Cambrian) explosion by 40 million years, they are already “modern-looking.”
Ancient fossilized Cambrian jellies compared to modern jellies – pictures
Moreover, the reproductive cycle of a Jellyfish is ‘metamorphic’,,
Do Jellyfish go through complete metamorphosis?
Excerpt: Yes, it looks different every stage of it’s life. Jellyfishes go through 2 stages. The polyp stage, then the medusae stage. When a jellyfish is a fertilized egg, it is called planula. When the planula is released from the pouches of the jellyfish’s tentacles, it will swim to the bottom of the ocean, attach itself, and start growing. This is known as the polyp stage. Then it will start “budding” and separate. The separated part would then grow into a jellyfish, which is known as the medusae stage.
bornagain77, I am going to make it my mission in life to find some topic that you don’t have a bunch of links for. 😉
Mung, there are plenty of subjects that I don’t have notes on, but I find the Jellyfish important to take notes on since they appear so early in the fossil record. Apparently even before the Cambrian explosion itself occurred:
Pre-Cambrian Explosion – Jonathan Wells – (How do you change a jellyfish into a trilobite?) – video
Response to John Wise – October 2010
“So, where then are those ancestors? Fossil preservation conditions were adequate to preserve animals such as jellyfish, corals, and sponges, as well as the Ediacaran fauna. It does not appear that scarcity is a fault of the fossil record.”
Sean Carroll developmental biologist