Secrets of Giant Antarctic Sea Spiders Revealed After 140 years

In the frosty depths of Antarctica's McMurdo Sound, a discovery has illuminated the mysterious world of giant Antarctic sea spiders and their unique approach to parenting. Unlike their marine counterparts, these sea spiders, known for their colossal leg spans of up to 20 inches, choose an unconventional method to care for their thousands of tiny eggs.

While most sea spiders carry their eggs on their backs until hatching, the giant Antarctic sea spiders defy this norm. The revelation comes after 140 years of scientific inquiry into the enigmatic reproductive strategies of sea spiders. Unlike their warmer-climate counterparts, this spider opts for "polar gigantism," growing significantly larger than its sea spider relatives. This particular sea spider belongs to the exclusive group of marine arthropods whose males are responsible for caring for their offspring. Amy Moran, a professor at the University of Hawai'i's School of Life Sciences at Mānoa, reveals that despite more than a century of research into sea spider reproduction, the brooding behavior of certain families, including Collossendeidae to which C. megalonyx belongs, had remained elusive.

To figure out how the Antarctic sea spider safeguards its eggs, divers plunged into the icy Antarctic waters, collecting individual spiders who were part of mating groups. Transported to the McMurdo Station research facility, the sea spiders were meticulously observed in tanks. Astonishingly, two separate pairs laid thousands of eggs, but the male took a unique approach. Rather than carrying the eggs as seen in other sea spiders, the male of the giant Antarctic sea spider spent two days affixing the cloud-like brood to the tank floor.

After a few weeks, the eggs, covered in a veil of algae, became challenging to discern within the tank. This overgrowth of algae could play a role in camouflaging the eggs against the seafloor in their natural habitat.