Deep-sea mystery solved: Alaska's 'golden orb' was giant anemone base

In August 2023, a remotely operated vehicle exploring the seafloor west of Prince of Wales Island as part of NOAA's Seascape Alaska mapping project spotted an unusual sight: a smooth, four-inch-wide golden orb firmly attached to a rock more than two miles underwater. The discovery baffled researchers. Initial theories ranged from an exotic egg casing to an unknown sponge species, but the specimen's true identity remained locked away in its peculiar structure.

Scientists at the Smithsonian's National Museum of Natural History, where the orb was sent for analysis, unlocked the mystery through careful microscopic examination and genetic testing. Under magnification, researchers identified specialized stinging cells called spirocysts—cellular structures found only in cnidarians, a group that includes jellyfish, corals, and sea anemones. Allen Collins, a zoologist at the museum, and his team compared the specimen's DNA to a similar sample collected in 2021. Whole-genome sequencing revealed both specimens were genetically nearly identical to Relicanthus daphneae, a species of giant deep-sea anemone so ancient and rare that it remains poorly understood by marine biologists.

What researchers discovered was not the anemone itself, but rather the durable outer layer, or cuticle, that once anchored the creature to the rock. Scientists believe the anemone either died or detached and migrated to a new location, leaving its basal structure behind—a phenomenon observed in R. daphneae before. "Everyone was like, 'What the heck? What is that?'" Collins recalled of the initial discovery, according to reporting from Live Science.

The finding, detailed in a paper posted April 21 on the preprint server bioRxiv, underscores how little remains known about Alaska's deepest marine ecosystems. Emily Crum, a spokesperson for NOAA Ocean Exploration, told the Alaska Beacon that the discovery highlights the importance of continued deep-sea exploration. The golden orb case also demonstrates why scientific collections and careful specimen preservation matter—nearly three years of analysis were required to answer a question that captivated researchers and the public alike when the mysterious object first surfaced from Alaska's frigid depths.