Sexy Stuff on the Reef - Ruby Brittle Stars Spawning

by B. N. Sullivan

Our favorite Caribbean dive destination is the Cayman Islands. In particular, we like to stay on Cayman Brac. From there we can make day trips by boat to dive at Little Cayman, in addition to diving the many excellent sites around Cayman Brac itself.

In fact, one of our favorite night dives anywhere is a site on the north coast of Cayman Brac known as Radar Reef, which reportedly got its name from a landmark visible to boats offshore -- the antennas at a nearby telecommunications facility.

You don't need to hire a boat to dive Radar Reef at night, since it is easily accessible from shore. There is a boat ramp at the shoreline end of Kirkconnell Street at Stake Bay. Some concrete steps alongside the boat ramp lead right into the water, making it incredibly easy to enter and exit the water.

Some undersea communications cables come ashore nearby, and the trick is to locate the cables where they lie on the sandy bottom near the boat ramp, and then follow them offshore to the reef. (They're actually quite easy to spot.) At the end of the dive, you simply follow the cables back to shore again. It's next to impossible to get lost there, as long as you keep the cables in sight.

We've been to Cayman Brac a number of times, and while there, we always do a few night dives at Radar Reef. The area is well populated with small creatures, so it is a macro photographer's paradise. Particularly plentiful are critters that only come out at night. One of those is the Ruby Brittle Star (Ophioderma rubicundum), which forages only at night and hides in crevices in the reef during daylight.

Just before 7 PM one dark August evening, we waded into the water next to the boat ramp, located the cables, and swam out to Radar Reef. Fortunately I had set up my camera for macro photography in anticipation of the small critters we expected to see. Still, we had no idea what an amazing sight we were about to chance upon.

Once we arrived at the reef, in about 45 feet (14 m) of water, we shined our lights around on the coral heads to look for photo subjects. I spotted a Ruby Brittle Star almost instantly. I photographed it, and then noticed there was another of the same species very close by. As I was preparing to photograph the second one, I noticed a third, and then another and another.

Jerry was right beside me, but shining his light on a different coral head. I finished taking a photo, and he nudged me to look where he was shining his light.

There we saw more Ruby Brittle Stars -- lots more. Dozens and dozens of these critters seemed to be appearing out of nowhere, converging on the reef. They were literally draping themselves all over the coral, the sea fans, and the sponges growing on the reef. We had never seen so many Ruby Brittle Stars in one place at one time. We both had the feeling that something was going on, but we didn't know what.

I took a few more photos, and then we began to notice that some of the brittle stars appeared to be standing up. We had never seen this behavior before, but here they all were, standing up on their tippy-toes, raising their disc-shaped bodies off the corals or sponges where they had been resting flat a few moments earlier. They were beginning to look like so many miniature footstools.

Now completely fascinated, I shot frame after frame of what to us was a novel behavior. Then all of a sudden, the critters -- still balancing on the tips of their rays -- began to eject clouds of tiny red beads into the water. It took just a few seconds for the realization to hit us: these brittle stars were spawning!




As soon as they finished expelling spawn, the brittle stars ceased their peculiar uplifted posture and dropped back down into their more usual flat position, rays extended around them. Some individuals were entwined with others, but now they all just lay there. With their spawning orgy over, the brittle stars became immobile. They seemed totally spent -- in more ways than one!

We noticed little else on that dive, and I never did photograph anything but the Ruby Brittle Stars that night. I was shooting film, and I very quickly shot the entire roll of 36 frames, all the while thinking what incredible luck it was that brought us there to just the right place, at just the right time, to witness this amazing mass spawning event.

The photos on this page all were taken during that one night dive at Radar Reef. These photos are 1:2 macros. To give you an idea of the actual size of these creatures, the body disc of the Ruby Brittle Star is about a half inch (1.3 cm) across.

I have reduced the size of some of the photos on this page so that they all would fit into the text. You can click on any of them to see a larger view. In particular, you may want to look at the enlarged view of the 4th and 5th photos, so that you can see the red spawn more clearly.

Caption: "Was it good for you??"