Mystery of Giant Antarctic Sea Spiders Reproduction Solved

Posted on February 19, 2024

Scientists have solved the 140-year-old mystery of how giant Antarctic sea spiders reproduce. University of Hawaii at Mānoa scientists were able to observe the reproductive behaviors of the sea spiders first-hand.

The researchers dove under the ice and hand-collected groups of giant sea spiders that appeared to be mating. They then transported the spiders to tanks for observation. Two different mating groups in the tanks produced thousands of tiny eggs. Most species of sea spiders carry the eggs until they hatch but the giant Antarctic sea spiders behave differently. One parent (likely the father) spent two days attaching the eggs to the rocky bottom where they developed for several months before hatching as tiny larvae.

UH Mānoa School of Life Sciences Professor and lead researcher Amy Moran, says in the announcement, "In most sea spiders, the male parent takes care of the babies by carrying them around while they develop. What’s weird is that despite descriptions and research going back over 140 years, no one had ever seen the giant Antarctic sea spiders brooding their young or knew anything about their development."

The researchers also noticed that the sea spiders eggs became overgrown with microscopic algae within weeks. This provided a perfect camouflage for the developing eggs.

PhD students Aaron Toh and Graham Lobert were part of the researchers that made the discovery. Lobert says about the camouflage, “We could hardly see the eggs even when we knew they were there, which is probably why researchers had never seen this before.

The researchers findings were published in Ecology in February 2024.

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