Mommy, How Does A Coral Make New Polyps?

[jonnybravo22]

The birds and the bees...sps style.

In my ongoing struggles to keep fuzzy sticks alive, I've been reading a lot about them. One thing stuck in my mind that led me to a super basic question that I don't understand.

"Each coral polyp is it's own unique animal". And a coral / frag is simply a collection of these unique polyp animals. That's all well and good. I watched some scientific animations of how an individual polyp lays down new calcium carbonate to grow the coral skeleton. But as the skeleton grows, where do the new polyps come from? If they are all unique animals, don't they need to be generated anew from some sort of reproductive activity? Sometimes I feel like such a newbie even after years of attempting to reef.

 

[macdaddynick1]

I think the term "œit's own animal" is a bit misleading. It's all the same tissue until it is physically divided. Just thinking about it logically, Corals are very similar to plants, like focus, in the regard that a lot of them can be chopped into million pieces, thrown into a rooting hormone and they will become their own separate plants. One difference is that there's no need for Corals to go through the rooting process.

 

[Tripod1404]

Corals are colonial animals. So "Each coral polyp is it's own unique animal" is more about the potential of each polyp to start a new colony, say of you frag it up and separate from the remainder of the colony.

On a colony, each poly is connected to each other by a encrusting tissue known as coenosarc that fills the gap in between them and allows each polyp to communicate with one and other, as well as share nutrients. This is the same tissue that encrust surrounding substrate as the coral grows or the same tissue that encrusts the growing tips of SPS. When this encrusting tissue gets at a certain distance from the nearest polyp, some cells in that tissue differentiate into a polyp, so a new polyp is born. This is why polyps of SPS corals are very evenly distributed, when the tissue feels it is far enough from the nearest polyp, a new polyp is made. Keep in mind tissue and polyps made this way are genetically identical to the first polyp that settled on the substrate. They are basically clones of that first polyp.

Corals can also sexually reproduce by producing eggs and sperm. Fertilized egg develops into a free swimming larvae that travels with ocean currents and eventually settles on a suitable substrate, which can be thousands of miles away from where it was born. Depending on the specie, the larvae can look anything from a spherical blob to a tiny primitive jellyfish-like or polyp-like disk. Coral larvae is very picky on where it is going to settle at, it can try out several locations. They generally get more desperate the longer the search takes as they have limited energy supply. Being picky is understandable as once it settles and morphs into a polyp, it can no longer move and will live the rest of its life there.