Scientists from the University of Hawaii have discovered an important reproductive behavior of giant Antarctic sea spiders, providing new insights into the development of these spiders and the broader marine ecosystem. This groundbreaking research contributes to the understanding of marine life in one of the world’s least studied regions.

Reproduction of giant sea spiders in Antarctica remained largely unknown to researchers for more than 140 years until now. Scientists at the University of Hawaii at Manoa traveled to a distant continent to witness the behavior of these mysterious creatures firsthand, and their findings may have broader implications for marine life and ocean ecosystems in Antarctica and around the world.

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

“In most sea spiders, the male father cares for the young and carries them as they develop,” said Amy Moran, UH Mānoa School of Life Sciences professor and principal investigator. “The surprising thing is that despite over 140 years of description and research, no one has ever seen giant Antarctic sea spiders give birth to their young, and no one knows anything about their development.”

Moran’s laboratory has been studying polar giantism for more than a decade. During a field research expedition to Antarctica in October 2021, Moran and a team including School of Life Sciences doctoral students Aaron Toh and Graham Lobert made a groundbreaking discovery. They dived under the ice, picked out giant sea spiders one by one that appeared to be mating, and carried them into tanks for observation.

To their surprise, two different mating groups produced thousands of tiny eggs. Instead of carrying the hatchlings until they hatched, as in most sea spider species, one of the parents (presumably the father) spent two days anchoring the eggs to the rocky bottom; The eggs developed there for several months and emerged as small larvae. The researchers’ results were published at: Ecology In February 2024.

“We are very lucky to be able to see this,” To said. “Being able to work directly with these magnificent animals in Antarctica meant we were able to learn things that no one else could know.”

A few weeks after spawning, the eggs became covered in microscopic algae, providing excellent camouflage.

“We could barely see the eggs even though we knew they were there, so it’s possible the researchers had never seen it before,” Lobert said.

Groundbreaking research

Renowned Antarctic biologist Lloyd Peck of the British Antarctic Survey, who was not involved in the research, said: “The general ecology and reproductive biology of marine species in Antarctica are extremely unknown and we only have data on a few species, one of which is in one of the least studied parts of the world’s oceans.” “It is of great importance in shedding light on how animals function.”