Molecular systematics of the deep-sea bamboo corals (Octocorallia: Isididae: Keratoisidinae) from New Zealand with descriptions of two new species of Keratoisis

Bamboo corals belong to a species rich and abundant group of octocorals that occur throughout the world's oceans, primarily in the deep-sea. Their study through morphological, ecological and evolutionary approaches has been problematic because of the extreme environments many of them inhabit and therefore the difficulty of obtaining good quality samples. However, new undescribed species have been commonly collected as part of invertebrate by-catch studies from commercial fisheries. In this study we describe two new species of deep-sea bamboo corals from New Zealand waters, including the Ross Sea (Antarctica) using morphological and molecular approaches. For the morphological description we used macro-structural characters such as branching pattern, color and polyp arrangement, along with axis architecture and sclerite shape and arrangement. The new species fit in the subfamily Keratoisidinae and the genus Keratoisis. Keratoisis magnifica n.sp. is characterized by having big, highly armed conical polyps and K. peara n.sp. has long, smooth internodes with an unusual nacreous lustre. Additionally, we amplified three mitochondrial genes (16S, igr4 and mtMutS), and obtained optimal topologies through maximum likelihood and Bayesian approaches. The resulting molecular phylogenies corroborated the status of the new taxa and elucidated their relationships to closely related species. Additionally, we show further genetic evidence that branching pattern, as previously thought, could be an unreliable character not only for Lepidisis/Keratoisis, but also for other genera within the Keratoisidinae.