Tropical Organism Ejects Its Digestive Tract in Defense Mechanism
Posted on June 23, 2015
A tropical filter-feeder organism ejects its digestive tract as a defense mechanism. Scientists noticed the organism, Polycarpa mytiligera, was throwing something at them, which turned out to be its eviscerated guts. The scientists say the organism has the ability to eviscerate and regenerate its gut within 12 days. The image above shows new tissue formation in the organism five days post-evisceration.
Polycarpa mytiligera, is a tropical ascidian that is a filter-feeder. It eats by by straining suspended matter and food particles from water. The ascidian uses a specialized filtering structure. It can also rebuild its its filtration organ, the branchial sac, within 19 days.
Dr. Noa Shenkar and her student Tal Gordon from the Department of Zoology at TAU's Faculty of Life Sciences and the Steinhardt Museum of Natural History and National Research Center observed a recurrent pattern of evisceration and finally rejuvenation in ascidians from the Gulf of Aqaba. The organism appeared dead after expelling its digestive tract but it was not.
Dr. Shenkar says in a statement, "Polycarpa are the most abundant ascidian species in the Gulf of Aqaba and one of the most abundant in the world. In the process of studying their distribution and depths, we noticed they would throw something at us and then immediately shrink and remain highly contracted and camouflaged. I was sure they had died, but something told me not to discard them. Sure enough, four days later, the organisms regained their composition -- as if they had been 'reborn.' This was very unexpected."
Dr. Shenkar also says, "All signs point to evisceration as a defense mechanism, and this alone is interesting. But this is also important and relevant to human research. Ascidians and vertebrates -- and humans are vertebrates -- share close affinities, so understanding ascidian regeneration pathways can point to promising new directions in human soft tissue regeneration research."
Here is some footage of the tropical ascidian eviscerating its guts:
A research paper on the unique defense mechanism can be found here in the journal, Scientific Reports.