A massive and potentially ancient antipatharian colony at a seamount in the Northwest Pacific

Anthozoans are ecosystem engineers and contribute to creating intricate benthic communities that often harbor high levels of marine biodiversity. Here, we report on an extraordinarily large antipatharian colony observed on the Ritto Seamount in the Northwest Pacific. Based on colony form and DNA barcoding results, we identified the colony as Leiopathes cf. glaberrima. From in situ observations, we estimate the size of the colony as approximately 308 cm in height, 441 cm in width, with a central stem of 27.9 cm in diameter. If growth rates of Leiopathes species in this region of the Pacific Ocean are similar to those previously reported from Hawai’i, this colony may potentially be approximately several thousand years old, placing it among the longest-lived marine organisms reported. Seamounts in this region and such large antipatharians and other anthozoan colonies should be targeted for more biodiversity investigation and future conservation.