Creature Feature: Ophiacantha bidentata! Deep-Sea Animal Profile by Keyla Pacheco

Today's special Echinoblog was written in part by my intern Keyla Pacheco from the Interamerican University of Puerto Rico!! She is supported by the NMNH Latino Students Initative and is a smart, enthusiastic worker and came up with many interesting bits! I welcome her input! Keyla is co-advised by myself and Martha Nizinski at the NMFS Lab!

(from Ross et al. NOAA, HBOI)

When we look at the deep-sea, we often see so many of some critters that they practically take on the landscape!

Today!-one of many articles on the importance of the ubiquitous!!

Today!-we treat a relatively common deep-sea critter that wouldn't normally get the uh..STAR treatment!! (sorry-this is my bit..chris)

Past blogs have focused on critters that have lived or taken advantage of coral as a living substrate. Ophiuroids are among the most frequently encountered of echinoderms that live in this fashion. Among them are the Ophiacanthidae! Where have we heard of these before?

They were all over the news when "Brittlestar City" was found!!

Ophiacanthids are ubiquitous-they are found in nearly all of the world's oceans. But how are they important?

Let's look at a widely occurring species and see:

Ophiacantha bidentata is a widely distributed species found in the shallow waters of the Arctic and in deep sea settings in the North Atlantic and North Pacific.

Dense populations of O. bidentata occur in the hundreds to thousands of individuals occurring among deep water coral habitats. Their abundance and dense aggregations in deep water coral habitats make this animal an important component of deep sea benthic communities.

O. bidentata lives on both soft bottoms but also as an inhabitant on reefs of the deep-sea coral Lophelia. This seems to go in hand with their ability to switch from deposit feeding to suspension feeding depending on food availability.

(from Wikipedia commons)

Because the protection of deep sea corals have become of increasing concern and a “hot topic”, studying species that present an important trophic resource within these communities is of greater interest.

Bigger ones apparently show greater incidence of regeneration..as well as a greater incidence of sublethal predation! This, in turn, seems to suggest that they provide a "renewable trophic resource"..i.e., food among these coral communities!!

So conceivably...fish come for the coral habitat, but stay for the brittle star arms!

Other Curious Facts:

1. Those found in the deep sea waters have shown to be protandric hermaphrodites, which means they start out as male and develop into female. This is apparently an uncommon reproductive strategy among ophiuroids.

2. The same(?!) species found in shallower waters tend to be gonochoric which means there are at least two distinct sexes which do not brood their young.

3. O. bidentata is bioluminescent!