Ostracods: the Seed Shrimp

Jack and I came up to Jeff Davies Memorial dive site just as the sun was setting. The dive site was a three-mile ride in the dinghy, but with only two of us, we could travel far in Edna. All four, plus dive gear and we can’t plane. We can go slowly moley, but it takes a long time to get somewhere.

The girls were invited by the Alchemist kids for dinner and a movie. This meant Jack and I were on our own. What were we going to do? Watch tv. Read. While I’ll take those options at the best of times, it was a night with a difference in Bonaire. It was ostracod night.

Five nights after full moon – as if the tiny seed shrimp get their astronomical calendars out, these ostracods perform an underwater ritual. In the time after the sun has set and before the moon has risen, they perform a light show en masse.

It seems an amazing feat considering these invertebrates can’t even fully see the moon. I doubt they go spy-hopping like a great white does. But apparently they still know it: exactly five days after full moon for full effect. And then they start their mating display.

With this, Jack and I dropped down just after sunset. We had about thirty minutes to wait until the ostracods began to light up. Jack dropped down first. Man he shoots down like a stone. I don’t like to go so fast. So we were at two different heights, flashlights on. No one and nothing around. No tarpon. No puffers. No eels. Just a wall of coral. And at twenty-five metres, a lot of bleached coral.

In the last couple of months, the plate corals in Bonaire have taken a bashing. Pardon the pun. Still, when we first started diving in August, the corals were brown. Now they’re mostly white. South of twenty metres the reef looks more like a ski-slope than coral. Hopefully, they’ll come back as temperatures are finally starting to drop for the Christmas winds. People are hoping,

We didn’t have much time to stare. The ostrocods’ show was supposed to take place at the top of the reef, among the soft corals.

Coming up, we turned our torches off. I’d read the shrimp won’t glow if they’re disturbed by any light. It was a bit unnerving at first, swimming in a lonesome place, in the pitch dark.

And did they really follow the five days after full moon rule? I can’t even time my menstrual cycle to be accurate, and I’ve spent literal years trying.

The answer is yes. Yes, they do. The whole place started to glow. I almost choked on my regulator! The shrimp form strings of lights – little, round fairy lights, before fading away. Jack and I watched for twenty minutes, marvelling at the sight. Kudos to the delicate seed shrimp. They know their astronomy.

And the lights were too delicate for our GoPro to capture. So I’m borrowing an image. From: https://divedivabonaire.com/event/ostracod-night-dive/. Thank you.

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