Description of the sea pen Calibelemnon hinoenma sp. nov. from shallow waters in southern Japan

Abstract

Sea pen species of the genus Calibelemnon are important components of soft bottom communities. Here, we formally describe Calibelemnon hinoenma sp. nov. from shallow waters in Amami Oshima, Kagoshima in the Ryukyu Islands, via molecular and morphological observations and analyses. This species can be distinguished from its congeners by the presence of paired autozooids, siphonozooids aligned irregularly in one to three rows at the side of the rachis between polyps, and the red-brown rufous color of the oral disks. Phylogenetically, the new species is located in an Anthoptilum–Umbellula–Calibelemnon clade. Ancestral state reconstruction analyses suggest that Calibelemnon species may have undergone at least two habitat changes, from shallow to deep waters, followed by a return to shallow waters. In the Ryukyu Islands, there have been many recent discoveries of unique marine species, with this sea pen species being the latest.