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header image Bioluminescent Courtship

Bioluminescent Ostracod CrustaceansBioluminescent ostracods on the Anse Chastanet Reef

Bioluminescent Sexual Courtship displays by Ostracod Crustaceans on the Anse Chastanet Reef

Donated Fluoro Light Image
Fluorescent detail of a resident brain coral shown up by Sea Life's Sea Dragon Fluoro Light
Thousands of these remarkable crustaceans, called ostracods, tumble out of the reefs just as twilight fades to darkness and the males produce a galactic symphony of blue lights that burst out in precise patterns. Imagine that you are a sesame seed sized guy cruising around in the sea at night trying to not only locate, but also attract, a hot female. How do you do it? Well, one way is to somehow advertise your location with pulses of light! You do this by squirting out molecules that emit light when mixed in seawater. You make a squirt of light, then another, and another …and as more pulses are produced in a row, the earlier pulses slowly fade away yielding what looks like a moving string of tiny glowing pearls in the water. These displays are unique to each species of ostracod, and up to a dozen species can be seen to display in one reef system. This results in a "Dazzling Blue Symphony of Lights!"

Donated Fluoro Light Image
Fluorescent polyp detail shone up by Sea Life's Sea Dragon Fluoro Light
Last month we hosted James G Morin here at Anse Chastanet and together with us here at Scuba St Lucia, researched the presence of Bioluminesent Ostracod crustaceans here on our local reefs.

On his first night snorkel here with us on the Anse Chastanet Reef, he witness 5 different kinds of displays by these intriguing creatures. These 5 different types of displays, each representing different species of ostracod! Some of these displays were even witnessed right underneath our entrance ladder, making this an activity that all levels of snorkeler could witness. These bioluminescent displays cannot be witnessed with normal light, you must be in darkness, so it is intense for some. Of course we have all snorkelers and divers wear glow sticks so we can be seen and also have a light available to them if in need.

Donated Fluoro Light Image
Fluorescent detail shone up by Sea Life's Sea Dragon Fluoro Light of a stationary SandDiver
At the time of the scientists visit there was also another impressive sight, a “plankton bloom” with numerous 8-10cm long “spot-winged comb jellies” (Ocyropsis maculata) in the water column, which when disturbed emitted a bright blue flash of light (these are ctenophores and are NOT jellyfish!). Also, high up on the cliffs along the forest above were numerous fireflies displaying with their delicate dimmer yellow lights, and rapidly flying super-bright yellow-white streaks of paired lights from fire beetles. And finally above all this biological light there was the starry sky. Magical.

Donated Fluoro Light Image
Fluorescent detail of a wideband tube dwelling ane shone up by Sea Life's Sea Dragon Fluoro Light
Other sites were dived at night during this week in order to find these displays, but the best were found on our house reef (Anse Chastanet Reef) accessible from shore. Why are these so impressive to see right from a resort beach? These displays cannot be seen with the impact of light pollution. Anse Chastanet is proud to have a natural beach with only the beach restaurant illuminated at night. This makes activity like this possible in the water- also it does disturb other natural processes like turtle nesting that occurs frequently on our beaches.

Donated Fluoro Light Image
Fluorescent detail of a resident brain coral shone up by Sea Life's Sea Dragon Fluoro Light
We hope to take this new insight into this interesting sight into our weekly night dives and snorkels. Predictable luminescent organisms include: the ostracods, syllid polychaete (segmented) worms, brittle stars, fireflies, fire beetles, and, if the plankton blooms coincide - comb jellies, dinoflagellates, larvaceans, and certain jelly fish! We have had a great donation from SeaLife Cameras, who have given us a prototype of their Fluoro Dual Light and mask set up so we can capture these amazing finds. Check out these pictures by in house photographer Bernd Rac when tested out this light!