Researchers discovered unexpected fans of sea urchins.

Confronted with the issue of sea urchin proliferation along the southeastern coast of Australia, local scientists aimed to identify which predators were preying on the burgeoning population of these echinoderms and could potentially help control their numbers. The experiment yielded unexpected results: it turned out that the "spiky delicacy" was not being targeted by the lobsters, who were initially thought to play this role.

2024-10-08 07:30:33https://naked-science.ru/article/biology/lyubiteli-morskih-ezhej

Climate change and ocean warming have led to an increase in the population of sea urchins in the waters off the southeast coast of Australia. This trend is concerning to scientists: since these echinoderms feed on seaweed, their southward expansion poses a threat to underwater forests of kelp.

Previous studies indicated that predators help control the spread of invasive species. One of the key “consumers” of sea urchins in Australian waters was previously thought to be the lobster species Sagmariasus verreauxi. The population of these crustaceans had once suffered due to overfishing, but the situation has improved in recent years. However, there has not been a significant decrease in the population of sea urchins as a result.

A group of ecologists and zoologists from the University of Newcastle (New South Wales, Australia) became interested in the situation. They suspected that the controlling role of lobsters regarding sea urchins may have been overestimated.

To investigate the matter, the scientists organized an experiment in 2023 in the waters near Wollongong—a city on the Tasman Sea coast. They set up several cameras for nighttime video recording near the lobster habitat, which operated for nearly a month. Special mounts were also used to place long-spined and short-spined sea urchins of the species Centrostephanus rodgersii and Heliocidaris erythrogramma. During the observation period, 100 sea urchins were used—50 of each species.

An article discussing the results of the experiment was recently published in the journal Frontiers in Marine Science. Analysis of the video recordings revealed that lobsters Sagmariasus verreauxi rarely showed interest in the bait, attempting to consume it in only 4% of the cases. Surprisingly for the researchers, it was found that 45% of the sea urchins were destroyed by bull sharks of the species Heterodontus galeatus and Heterodontus portusjacksonii, which inhabit the waters off Australia.

The scientists noted that sharks had no trouble consuming even large long-spined sea urchins, which reached 12 centimeters in diameter. It was previously thought that their long spines deterred most predators. However, the sharks attacked their prey without regard for the spiny defense.

Lobsters preferred smaller individuals as well as sea urchins with short spines. They attempted to flip the echinoderms over to attack from the more vulnerable underside.

The study indicated that Australian bull sharks may play a more significant role in regulating sea urchin populations than previously assumed. Nonetheless, the authors of the scientific paper noted that the experiment took place in a single location and under artificially created conditions, so the results require further validation.