The seabed off Spitsbergen was also explored with the JAGO submersible.

enckenberg scientist Max Wisshak and his colleague Christian Neumann from the Museum of Natural History in Berlin documented the struggle for survival of a sea urchin on the seabed off Svalbard.

In their study recently published in the journal “Polar Biology”, they show that, despite serious injuries – more than a third of his shell and important organs were missing – the sea creature from the Strongylocentrotus genus continued to move over the sea floor for at least 43 hours, even doing so Avoiding attack by a large crab. The case documents the high regeneration capacity of the sea urchins that was built up in the course of their evolution.

Echinoderms, which include sea urchins, starfish and sea cucumbers, have a good ability to regenerate: for example, starfish can replace entire arms and, in special cases, even allow further arms to grow from a single arm. “There are already some studies on the self-healing powers of starfish, whether sea urchins also have such abilities, but little research has been done so far,” explains Dr. Max Wisshak von Senckenberg am Meer in Wilhelmshaven and continues: “Using a series of photos from the sea floor in front of Svalbard, we were now able to directly observe the resilience of one of these animals in its natural environment.”

The spectacular pictures were taken in 2016 during an expedition to the Spitsbergen with the research ship Maria S. Merian, in which an experiment platform with measuring devices and an automatic camera system was placed on the seabed for a week. The protagonist of the sea urchin also came into view: an approximately 38 millimeter large sea urchin from the Strongylocentrotus genus . “Despite a large hole in the protective shell, which was supposed to be where his sexual organs, anus and other important organs were supposed to be, we were able to observe how the small sea creature continued to move on the sea floor for 43 hours and 20 minutes. The sea urchin was even able to avoid an attack by a large crab! ”Explains the Wilhelmshaven geobiologist.

According to the study, the reason why the small sea urchin survived so long despite its deadly-looking wound is that sea urchins have a decentralized nervous system instead of a real brain that continues to function even in the event of serious injuries. How the sea urchin got damaged is unclear. Among other things, the animals are on the menu of fish and large crabs, which can break open the shell of the sea urchin and absorb the soft organs. “A natural injury is therefore quite possible. Unfortunately, we cannot rule out that we ourselves injured the echinoderm when lowering our research equipment, ”said Wisshak. If the latter were the case, the sea urchin would have been in its condition for 4 days before it came into the field of view of the camera.

It is also unclear whether the sea bottom dweller survived after the recordings were stopped. “We know some of the shells in fossil sea urchins that have broken considerably in the shells, which then healed completely. We therefore believe that sea urchins – like their relatives, the starfish – have high regeneration abilities and assume that self-healing is part of their evolution in order to have a better chance of survival as a prey, ”concludes Wisshak.

Wisshak, M., Neumann, C. (2020) Dead urchin walking: resilience of an arctic Strongylocentrotus to severe skeletal damage. Polar Biol 43, 391-396.