by Les Watling, University of Hawaii at Manoa
June 23, 2019
When someone mentions deep-sea corals, most people think of something like what they might see on a tropical shallow coral reef. But many deep-sea corals, like the colonies in this video, are more closely related to tropical sea fans than to the corals that create the structure of the reef.
One of the most common deep-sea corals are called bamboo corals. These corals get their name from the (admittedly slight) resemblance they have to bamboo stalks. That is, their skeleton is composed of little black “nodes” separated by the white “internodes.” The earliest bamboo corals pulled up by dredges in the 1800s were missing a lot of the living tissue, so the skeleton was more visible than what we see in the remotely operated vehicle (ROV) images of living colonies.
So, what kind of bamboo coral is in this video? Unfortunately, we can’t say because it has most likely not been named and described, and perhaps has not even been seen before. When I started working on the taxonomy of this group about 15 years ago, most of the names were from more than 100 years ago. We have now collected more than 300 specimens from ocean exploration cruises dating back to 2004. The result is that we have a very large number of previously unknown species that are in need of naming and describing.
Bamboo corals can grow in a large variety of different colony forms. Most common are unbranched colonies, called “whips,” but there are also bushes, fans, and colonies that live close to the ground that we call “brambles.” The colony in this video has a classic fan shape. The colony doesn’t have a strong main axis, instead, branches produce other branches over and over.
Bamboo corals are members of the group of corals called octocorals. The polyps have eight tentacles armed with little side branches called pinnules that are characteristic of octocorals. There are many groups of octocorals in the deep sea, and most inspire awe in people who are watching the dive over the internet.