Sponges are among the oldest living things on earth and play an important role in many underwater ecosystems. New research has found that sponges “sneeze” to clean waterways. With each sneeze, the sponge releases a type of mucus that is eaten by other animals.
The study was conducted by Niklas Kornder of the University of Amsterdam (UvA) and colleagues, and the results were published today (August 10, 2022) in the journal Science. Current Biology.
Fossil evidence suggests that sponges date back 650 million years, making them among the oldest animals on the planet. They may seem like simple creatures at first glance, but sponges play a key role in many underwater ecosystems. They feed by filtering up to thousands of liters of sea water every day, drawing water from the network of inlet and outlet channels in their bodies. By improving this process, the sponge is able to feed on dissolved organic matter, a food source unavailable to most other marine life.
After feeding on dissolved organic matter, the sponge produces a waste carrier such as mucus. “The waste was expected to be released with water flowing through its pores,” Kornder explains. To study this theory, scientists took samples of purple tube sponges and placed them in an aquarium to collect mucus. They also placed a camera to capture a time-lapse of the sponge surface.
When analyzing the video footage, the researchers were surprised, Kornder shares: “Every three to eight hours, the sponges contract and then relax their surface tissues. At first, we temporarily stopped paying attention, but we quickly realized that the animals were “sneezing”.
Time-lapse images of the Indo-Pacific sponge Chelonaplysilla sp. Credit: Current Biology/Kornder et al
The images revealed that the accumulated mucus during each sneeze is released and the sponge is left with a clean surface. Although sponge sneezes have been described before, it was generally thought of as a sponge’s way of regulating water flow. The time lapses also showed that the mucus was continuously flowing out of the inlet holes rather than through the flow holes, and that the accumulation was slowly transported by different pathways to central points on the surfaces of the sponges.
While diving in the Caribbean, scientists have seen many tiny creatures that feed on the energy-rich mucus in sponges. This directly shows how the sponge benefits the entire ecosystem by harnessing the energy of dissolved organic matter in the water and turning it into a food source to enter the food chain.
“A sponge sneeze is not exactly the same as a human sneeze, because a sneeze lasts about half an hour,” says Kornder. “But they’re really comparable, because for both sponges and humans, sneezing is a mechanism for getting rid of waste.”
Time-lapse images of the massive tube sponge Aplysina. Credit: Current Biology/Kornder et al
Such behaviors show the incredible flexibility of sponges to adapt to the environment that allowed them to evolve over 650 million years. The team plans to continue studying sponge sneezes.
“By combining electron microscopy with histological studies, we want to investigate the underlying mechanism,” says Kornder. They will also include more types of sponges.
Reference: “Sponges sneeze mucus to shed waste from seawater entry pores” by Niklas A. Kornder, Yuki Esser, Daniel Stoupin, Sally P. Leys, Benjamin Mueller, Mark JA Vermeij, Jef Huisman, and Jasper M. de Goeij, 10 August 2022 , Current Biology.