View Full Version : 9 days after full-moon, 1 hour after sunset - Precisely!
All of us reef enthusiasts may/must know exactly what the title refers to ... so, what's so special about that?
dogstar74
02/03/2010, 07:26 PM
Spawning event
inktomi
02/03/2010, 08:11 PM
Do we know how corals (among other 'lower' life forms) time these events so precisely? Fish, corals, lots of our favorite sea creatures do this sort of timing - but how do they do it?
Is this still a big mystery of science?
jhawkor
02/03/2010, 08:13 PM
Do we know how corals (among other 'lower' life forms) time these events so precisely? Fish, corals, lots of our favorite sea creatures do this sort of timing - but how do they do it?
Is this still a big mystery of science?
I'm sure there are some theories.
inktomi
02/03/2010, 08:18 PM
Yea, I'm aware of some of them - cycles of the moon, etc.. but it seems to me that a single coral polyp probably can't accurately 'count' cycles of the moon, day/night cycles, etc.
tufacody
02/03/2010, 08:19 PM
full moon makes us randy baby, yea!
ChadTheSpike
02/03/2010, 08:25 PM
my uneducated but thought out thoughts are that it is based on chemical cues. i think there is a lot more going on chemically than we know.
Chiefsurfer
02/03/2010, 09:12 PM
I think it is solely based on the moon. I don't know about sunest(do you mean outside, or in the tank?). It has been a fairly commonly accepted theory among fisherman that fish, crabs, and inverts alike can feel barometric changes of an approaching storm. They then go frantic eating to stock up, as the larger the storm, the larger the likelyhood that they will end up in a strange area, and food may be scarce til they can find a new good hunting ground. Natural crabs in saltwater shed their shells 3 days +/- a full moon. Full moons and new moons create unusually high tides because the moon's and sun's gravities pull opposite one another. Think about the image of an egg transposed over the image of a golfball. The golfball being earth, and the egg being the surface of the water. Depending on the area, tide shifts can be huge. Anywhere from 3-4 ft from low tide to high tide is VERY normal where I live on the coast. A gravitational field that can move millions of billions of gallons 3-4 ft higher than they were 6 hours before has a tremendous amount of energy. While we humans may not feel it, I bet that many of our corals, crabs, shrimp, etc. have hypersensativity to such small changes in barometric pressure. Also, the effects of this change affect water much more than air, since air is compressable, and water is not.
Sorry to sound like a huge nerd, but that's what I know of it. Why 9 days, that I cannot answer.
inktomi
02/03/2010, 09:15 PM
That's interesting, and I agree - corals, etc, can probably sense changes in pressure more than we can.
What I'm curious about is how they time or count them. For example, corals don't spawn after /every/ full moon, only some - but they all seem to know which one is the right one for their species.
ser_renely
02/03/2010, 09:18 PM
wow interesting.
Chiefsurfer
02/03/2010, 09:35 PM
yeah, that I don't know about timing them and what-not. Do you find that let's say you have an acan, and I have an acan(hoping that acans spawn, not even sure) that both will skip the same number of cycles? If that's the case, that's very interesting to think about. That I don't know. I only know about fish behaviour of a storm, and crab behavior with a moon. I know most fish that are local, are usually set-off to spawn by a specific temperature in conjunction with their food. Interesting.
shroutk3
02/03/2010, 09:38 PM
they don't "time" these events, but likely respond to solar cues -angle of sun and day length combined with a lunar cycle could trigger incredibly accurate events. Polyp to polyp communication is more than likely accomplished with chemical messengers.
Note: this is my educated guess based on what I know about seasonal responses in many other types of organisms. I have never looked into coral mass spawnings in depth.
inktomi
02/03/2010, 09:52 PM
That's true. Day length cycles, in theory, would only repeat twice a year as the days get slightly longer and then slightly shorter. That's probably part of the cue that's used.
How many times a year do corals spawn in mass in the wild?
I assume that the angle of the sun would be a lesser factor, due to it's very slight change at or near the equator, and even then... wouldn't the angle of the sun impact the surface temperatures more than anything? (and then, wouldn't currents wash that away?)
greenbean36191
02/04/2010, 10:02 AM
Nobody knows how the events are timed but there are some basic ideas.
First, we know that most corals don't even start producing gametes until a few months before they're ready to spawn. The initiation of the gamete production is almost definitely linked to seasonal temperature variations. Once the water starts warming and stays warm for a while it kickstarts the process. Until they've been primed, nothing else even matters. There's no need to worry about lunar cycles if you have no gametes to release.
After they're ripe, then other signals come into play. Although corals are apparently able to sense moonlight, it's unlikely to play much of a role in the timing of spawning. Part of the reason is that it's an unreliable signal. Clouds, heavy seas that stir up sediment, or even a plankton bloom can all affect the signal. It's much more widely accepted that it's tidal variations that are the actual cue.
How do they know that the tidal flow will be weakest X days after the full moon and then count off that time? No one really knows yet.
However, once one coral starts spawning, chemical cues are released that will induce other corals nearby to go off as well, so even if most corals are bad counters, you still get a synchronized effort. Often cues from one species can set off multiple others as well, including other inverts like snails.
Contrary to popular belief though, there's not some set time all the corals of the world spawn. Corals on different reefs spawn at different points in the lunar cycle and often we're only able to predict it to within a week or two from year to year. Some species may spawn only one night, while others may spread their effort out over several days. On some reefs the whole event is over within 2 or 3 nights, while others it goes on for weeks.
Chiefsurfer
02/04/2010, 10:35 AM
^See, now that is a really good answer if I saw one. Thank you greanbean for your excellent response.
to OP, maybe yours runs off a cue that happens to occur exactly that time of the month, year, etc. for you.
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