Mystery of Antarctic giant spider reproduction solved by researchers

The reproduction of giant sea spiders in Antarctica has been largely unknown to researchers for more than 140 years. Scientists from the University of Hawaii at Mānoa traveled to this remote continent and were able to directly observe the behavior of these mysterious creatures. Their findings could have broader implications for marine life and ocean ecosystems in Antarctica and around the world. The researchers’ results were published in Ecology.

Sea spiders, or pycnogonids, are a group of spider-like invertebrates found in marine habitats around the world. Most species are smaller than a fingernail, but some Antarctic species have a leg span (from the tip of one leg to the tip of the opposite leg) of more than a foot. These animals are a famous example of “polar gigantism,” a phenomenon in which some organisms in polar regions, such as the Arctic and Antarctic, grow to much larger sizes than their relatives living in warmer climates.

“In most sea spiders, the male parent cares for the babies by carrying them around as they develop,” said Amy Moran, a professor in the UH Mānoa School of Life Sciences and lead researcher. “The strange thing is that despite descriptions and research going back more than 140 years, no one had ever seen the giant Antarctic spiders brooding their young or known anything about their development.”

Moran’s lab has been studying polar gigantism for more than a decade. In October 2021, during a field research expedition to Antarctica, the team, including Moran and School of Life Sciences Ph.D. students Aaron Toh and Graham Lobert made a groundbreaking discovery. Diving beneath the ice, they collected groups of giant sea spiders that appeared to be mating by hand and transported them to tanks for observation.

To their amazement, two different mating groups produced thousands of tiny eggs. Instead of carrying the babies until they hatched, as is the case with most sea spider species, one parent (probably the father) spent two days attaching the eggs to the rocky bottom where they grew for several months before hatching as tiny larvae.

“We were so lucky to be able to see this,” Toh said. “The opportunity to work directly with these amazing animals in Antarctica allowed us to learn things no one had ever imagined.”

A few weeks after laying, the eggs were invaded by microscopic algae, providing perfect camouflage.

“We could barely see the eggs even though we knew they were there, which is probably why researchers had never seen this before,” Lobert said.

Lloyd Peck, a renowned Antarctic biologist with the British Antarctic Survey who was not involved in the study, said: “The general ecology and reproductive biology of Antarctic marine species remains extremely unknown and we have no data only on a handful of species. one of which is critically important in shedding light on how animals function in one of the least studied regions of the world’s ocean. »