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.

Ruby Brittle Star (Ophioderma rubicundum)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.

Ruby Brittle Stars (Ophioderma rubicundum)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.

Ruby Brittle Star (Ophioderma rubicundum)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!

Ruby Brittle Star (Ophioderma rubicundum)
Ruby Brittle Star (Ophioderma rubicundum)

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.

Ruby Brittle Stars  (Ophioderma rubicundum)Caption: "Was it good for you??"

13 comments:

  1. This must have been really exciting. I think macro photography is just amazing. I would have never thought the body of this was only 1/2 an inch which makes these pics even more amazing. Thanks for suggesting the pics to look at. I might have missed it! Awwww-sum! :-)

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  2. Hi 2Sweet - It certainly was exciting. We'd never seen anything like that before.

    I'm having second thoughts now about making those spawning photos so small. I may have to re-do them in a larger size so that readers can see the important bits without having to enlarge them.

    Bobbie

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  3. UPDATE: So, I did go back and make the 4th and 5th photos bigger. ;-}

    Bobbie

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  4. wow, what a strange creature, thanks for sharing.

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  5. Thanks for sharing this phenomenon. Love the caption! :D

    Tink *~*~*
    My Mobile Adventures *~*~*

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  6. WOW! I would have loved to have seen that! Brittle stars are one of my favorite creatures. I have seen sea urchins spawning a few times, but never brittle stars. Just seeing all those brittles at once must have been amazing.

    I am also a big fan of the Cayman Islands, but I've never been to Cayman Brac, only to Grand Cayman. (In fact, I am planning a trip back there this fall.) That site where you can easily shore drive at night sounds so cool, though. The best of both worlds--shore AND night!

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  7. @ Ankush - You're welcome. Thanks for stopping by.

    @ Tink - I wasn't sure anyone would notice the caption, so I'm glad to know you did and that you liked it. ;-)

    @ Laura - I remember you liked the crinoids, too. You really do love echinoderms, don't you!

    Some time when you go to the Caymans, make the effort to get to Cayman Brac/Little Cayman. You'll love it. Little Cayman's Bloody Bay Wall is THE primo dive site in the whole Caribbean, IMHO.

    Bobbie

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  8. Wow! These are stunning. Lucky you for being there to catch this!

    -smarmoofus

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  9. Thanks, Smarmoofus - Yes, it was our great good fortune to be there at the right place and time to witness this.

    Bobbie

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  10. Wow! They are certainly tiny, and the eggs are even tinier, but you captured them so clearly. What an experience!

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  11. Hi Kathy - Thanks. The worst part was that I shot these on film, so we didn't even know until days later if I actually had been able to capture the spawning. Since this was a one-night occurrence, I would not have had a chance for a "do-over," but fortunately things turned out rather well.

    Bobbie

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  12. Wow - I think this is my favorite so far, but I have to go take a cold shower!
    Keep up the good work!
    Anna

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  13. Thanks, Anna. Hope you can recover in that shower!

    Bobbie

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We welcome your comments and invite your questions. Dialogue is a good thing!

Bobbie & Jerry