Luminescent organisms in ocean - what are they?

David_G_Muir at David_G_Muir at
Sun Sep 4 15:18:11 EST 1994

Most of the luminescent organisms are dinoflagellates, which are eukaryotic
unicellular organisms. The commonest is one called Noctiluca- it is easy
to recognize, because the cell is very large- up to a mm across, and easily
visible. There are many other dinoflagellates that are luminescent, however
nad the most important is Gonyaulax. This, like Noctiluca, can occur in such 
large numbers as to color the water red- hence "reed tides", but whereas
Noctiluca is harmless, Gonyaulax (some other dinoflagellates) are highly
toxic, and are responsible for fish kills, as well as producing PSP-
paralytic shellfish poisoning, which occurs when we eat filterfeeders
like clams that have accumulated the toxins. The mechanisms od luminescence
are complex-it is an enzymatic reaction, but the exact purpose is not known.
Many other organisms make use of bioluminescence, however- lots of fish, for

example, have colonies of symbiotic luminecent bacteria, which are prokaryoes
These are usually Vibrio's (fischeri is one species). They dont flash like
dinoflagellates, which only produce pulses of light, but instead shine con-
tinuously, so they make usefull lighting and signalling devices in the dark-
fish, squid, crustacea and lots of other things   use them. (I believe that
there is a scientific american article on this topic, but can't remember
how far back.) 
I forgot to mention that the dinoflagellates are mostly photosynthetic
but have a strange ability to also be heterotrophs- Noctiluca is predominant-
ly predatory. 

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