Madrid, 26 (Europe Press)
A water animal known as a sponge is often described as quite sluggish – once it has settled in one place and matured, it is not generally believed to move.
But this has been challenged by a new study published in Current Biology, in which researchers describe mysterious pathways of light brown sponge-like reticulae (the spike-like supporting elements in the sponge) across the sea floor in the Arctic.
“We observed traces of densely interwoven spicules directly attached to the undersides or lower wings of sponges, suggesting that these traces are traces of sponge movement,” the researchers led by Teresa Morganti of the Max Planck Institute for Marine Microbiology and Utton wrote. Purser, from the Alfred Wegener Helmholtz Center for Polar and Marine Research.
“This is the first time that abundant traces of sponges have been observed on site and attributed to sponge movement,” they add.
It was as if the sponges had “crept” into their present positions. In fact, sponges have an mobile larval stage. However, most species are thought to become sessile when they are adults. After all, sponges do not have specialized muscles or organs for movement. They can respond to external stimulation and move a little by contracting or expanding their body. There was also some evidence of the movement of lab-grown sponges. In some cases, this movement involved completely reshaping the body.
However, the new findings surprised the research team. The discovery was made by studying a video taken in 2016 by the research icebreaker Polarstern while surveying the permanently submerged Langseth Ridge peaks.
The Sea-Cut Camera Slide and Hybrid Remote Operated Vehicle (HROV) showed that the hilltops were covered by one of the densest spongy communities ever built. The researchers determined that the remarkable sponge populations mainly consist of large numbers of Geodia parva, G. hentscheli, and Stelletta rhaphidiophora individuals.
They say it is unclear, given the difficult environment, how the area supports such a vast spongy community. But even more interesting are the many effects of sponge lattices. Far from being rare, researchers have seen traces in nearly 70% of seafloor images containing live sponges.
These corridors were several inches and several meters long. Often they were attached directly to live sponges. Trails are seen in areas with many sponges, as well as in less densely populated areas. Researchers report that they often also appear in areas with juvenile sponges.
Researchers have produced 3D models from photos and videos to show how the paths are intertwined with one another. They say the results indicate that moving the sponge sometimes changes direction. They don’t think movement is just a matter of attraction. In fact, the photos indicate that the sponge was traveling uphill frequently. The sponges may move to get food, possibly due to the scarcity of Arctic resources.
“All of these characteristics are indicative of the behavioral trends in feeding and population density previously observed in sponge packaging,” the researchers wrote.
“ The extremely low primary productivity, sedimentation, and particle oscillation rates of the Langseth Ridge area generally lead to some of the lowest stocks of benthic life, so this Arctic geodia community is likely to rely on the particulate and dissolved parts of organic degradation waste trapped within the spinal mat as additional food sources. We suggest that the movement indicated here may be related to the sponge that searches and feeds directly on the clumping material accumulated confined within the sponge mat under the living sponge, “they explain.
The movement may also have to do with the reproduction or dispersion of the young sponge. To learn more about how often and why the sponge makes these unexpected movements, they say more time-lapse imaging and other studies are needed.