Mysterious Ocean Floor Trails Show Arctic Sponges On Move

The aquatic animal referred to as the sponge is usually described as entirely sessile: once they’ve settled during a spot and matured, they aren’t generally thought of as moving-around . But, consistent with latest study within the journal Current Biology on April 26—in which researchers describe mysterious trails of light brown sponge spicules (spike-like support elements in sponges) across the Arctic seafloor—that isn’t always so.

“We observed trails of densely interwoven spicules connected on to the underside or lower flanks of sponge individuals, suggesting these trails are traces of motility of the sponges,” the researchers, led by Teresa Morganti of the Max Planck Institute of Marine Microbiology and Autun Purser of the Alfred Wegener Helmholtz Centre for Polar and Marine Research, write. “This is that the first time abundant sponge trails are observed in place and attributed to sponge mobility.”

It looked as if the sponges had “crawled” into their current positions. In fact, spongs do have a motile larval stage. But most species are thought to become sessile as adults. Sponges, after all, haven’t any muscles or specialized organs for moving-around. they could react to external stimulation and move a small by contracting or expanding their bodies. There also has been some evidence of movement in sponges raised within the lab. In some cases, that movement involved remodeling their whole bodies.

Nevertheless, the new findings took the research team all of sudden. Discovery was made by studying video captured in 2016 by the research icebreaker Polarstern because it surveyed the submerged peaks of the permanently ice-covered Langseth Ridge.

Sponge Trails on the Seafloor

A towed marine camera sled and a hybrid remotely operated vehicle (HROV) showed that the peaks of the ridge were covered by one among the densest communities of sponges that’s ever been seen. The researchers determined that the impressive sponge populations were primarily comprised of huge numbers of Geodia parva, G. hentscheli, and Stelletta rhaphidiophora individuals.

They say it’s not clear, given the challenging environment, how area supports such a huge community of sponge. But, even more intriguing were the various trails of sponge spicules. faraway from a rarity, the researchers saw trails in nearly 70% of seafloor images that contained living sponges.

Those trails were several centimeters tall and up to several meters long. They often connected on to living sponges. the paths were seen in areas with many sponges, also as in more sparsely populated areas. The researchers report that they also often appeared to be in areas with smaller, juvenile sponges.

*Typical sponge spicule trails*
*Source : phys*

The researchers generated 3D models from the pictures and video to point out the way the paths were interwoven with one another . they assert that the findings suggest that the moving sponges sometimes change direction. They don’t think the movement is just a matter of gravity. In fact, the pictures suggest that the sponges frequently traveled uphill. it might be that the sponges move so as to urge food, perhaps driven by the scarce Arctic resources.

“These features are all indicative of feeding and population density behavioral trends previously observed in encrusting sponges,” the researchers write. “The extremely low primary productivity, sedimentation, and particle advection rates of the Langseth Ridge region overall end in a number of rock bottom stocks of benthic life; so potentially, this Arctic Geodia community relies on particulate and dissolved fractions from the degradation of old organic debris trapped within the spicule mat as additional food sources. we propose that the mobility indicated here could also be associated with sponges checking out and feeding directly on the accumulated detrital matter trapped within the sponge spicule mat underlying the living sponges.”

It’s also possible that the movement has something to try to to with reproduction or the dispersal of young sponges. to find out more about how briskly and why the sponges make these unexpected moves, they assert that further time-lapse imagery and other studies are needed.

The findings are reported on Cell Press