### Rediscovered Marine Worm Found After 70 Years in Pygmy Seahorse Photos

A marine worm species not seen for nearly seven decades has been rediscovered, thanks to detailed underwater photography. Researchers examining photos of tiny seahorses, each less than an inch long, uncovered hundreds of these elusive worms, known as Haplosyllis anthogorgicola, residing within coral colonies from Japan to Australia.

The species, a type of bristle worm or polychaete, measures about 0.24 inches (6 millimeters) in length and typically inhabits the branching gorgonian corals at densities of up to 15 worms per cubic centimeter. The worms were last observed in the wild in 1956, identified by Kyoto University marine biologist Huzio Utinomo. Their recent identification, reported in the journal Proceedings of the Royal Society B: Biological Sciences, marks a significant breakthrough.

The lead author of the study, Chloé Fourreau from the University of the Ryukyus in Okinawa, Japan, noted the difficulty in spotting these nearly transparent worms underwater. The research team took advantage of images shared by citizen scientists on the iNaturalist platform, finding that 489 photos of pygmy seahorses also contained these worms.

In their pursuit, researchers discovered that about 84% of the photographed coral colonies alongside pygmy seahorses hosted these worms. The worms' presence was evident through their tunnels and occasional appearance on the seahorses themselves. Mostly seen with only their antennae and trailing appendages visible, these worms appear to spend much of their time encased in their coral burrows, possibly feeding off the coral's environment or cleaning it.

This discovery expanded the known habitat range of H. anthogorgicola, suggesting they inhabit regions far beyond what was previously recorded, including Australia, East Timor, Indonesia, Malaysia, New Caledonia, Papua New Guinea, the Philippines, and Taiwan. Previously, these worms were associated with only one coral species, Anthogorgia bocki, but the recent analysis suggests they thrive in multiple coral species within the genus.

The unexpected finding, initiated by study coauthor Ai Takahata’s research into pygmy seahorses, underscores the potential of utilizing imaging data from more commonly studied species to uncover information about lesser-known ones. This approach has provided significant insights into the distribution and behavior of these elusive marine worms, revealing their integral role in their ecosystems and raising new questions about their interactions with corals and other coral-dwelling organisms.