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Mysterious submarine trail shows Arctic sponges on the move



Sponge Trail

This image shows the traces of the sponge as it crawls on the bottom of the sea. Picture courtesy: AWI OFOBS team, PS1

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People usually describe this kind of aquatic animals, called sponges, as completely stalkless: once settled and matured, they are usually not thought to move around.However, according to a new study in the journal Current biology On April 26, 2021, researchers described the mysterious trail of light brown sponge needles (nail-like supporting elements in the sponge) across the Arctic ocean floor.

The researchers were written by the Alfred Wegener Helmholtz Center for Polar and Marine Research, led by Teresa Morganti and Autun Purser of the Max Planck Institute for Marine Microbiology. “This is the first time that a large number of sponge traces have been observed in situ. This is due to the fluidity of the sponge.”

It seems that the sponges have “climbed” into their current position. In fact, sponges do have active larval stages. However, most species are considered sessile in adulthood. After all, sponges have no muscles or specialized organs for exercise. They can respond to external stimuli and move slightly by contracting or expanding their bodies. In the laboratory, there is also some evidence that the sponge is moving. In some cases, the exercise involves reshaping the entire body.

However, the new findings surprised the research team. The discovery was made by studying a video taken by the icebreaker Polarstern in 2016, which investigated the submerged peaks of the permanently snow-covered Langseth Ridge.

The towed marine camera sled and hybrid remote-controlled vehicle (HROV) showed that the peak of the ridge was covered by one of the densest sponge communities ever. The researchers determined that the impressive sponge population is mainly composed of a large number of Geodia parva, G. Individual composition of hentscheli and Stelletta rhaphidiophora.

They said that given the challenging environment, it is unclear how the area can support such a large sponge community. However, what is more interesting is the countless traces of sponge needles. The researchers found that in almost 70% of the seabed images containing live sponges, no traces were found.

These trails are several centimeters high and several meters long. They are usually directly connected to the movable sponge. This trail can be seen in areas with many sponges and sparsely populated areas. Researchers report that they also seem to be in the smaller baby sponge areas often.

Typical Sponge Trail

The figure shows a typical sponge stitch.Image source: AWI OFOBS team, PS101; Morganti et al./Current Biology

The researchers generated 3D models from images and videos to show how the paths intertwined with each other. They said the results of the study show that moving sponges sometimes change direction. They don’t think that movement is just a matter of gravity. In fact, these images show that the sponge is often driving uphill. It may be that the sponge is moving to get food, which may be due to scarce resources in the Arctic.

The researchers wrote: “These characteristics predict the behavioral trends of feeding and population density previously observed in sponges.” “The primary productivity, sedimentation and convection rates in the Langseth Ridge area are extremely low, resulting in some of the lowest benthic organisms overall. Population size; therefore, it is potentially that this Arctic Geodia community relies on the particles and dissolved parts produced by the degradation of old organic debris captured in the pincushion as an alternative food source. We suggest that the mobility indicated here may be It is related to the sponge searching for and directly preying on the debris accumulated in the sponge needle cushion behind the live sponge.”

The movement may also be related to the reproduction or spread of young sponges. In order to better understand the speed of movement of sponges and why they make these unexpected movements, they said that further time-lapse imaging and other studies are needed.

Reference: “In situ Sponge traces observed indicate the common sponge sport “Central Arctic deep, Author: Teresa M. Morganti, Autun Purser, Hans Tore Rapp, Christopher R. German, Michael V. Jakuba, Laura Hehemann, Jonas Blendl, Beate M. Slaby And Antje Boetius on April 26, 2021 Current biology.
DOI: 10.1016 / j.cub.2021.03.014

This work was supported by the DFG Excellence Cluster “Ocean in the Earth System” of the University of Bremen, which came from the ERC Adv Grant ABYSS, the European Union’s Horizon 2020 Research and Innovation Program, the Helmholtz Society, and Max Plan Gram society and NASA.




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