Why Animals?

I am wondering why we call corals animals? According to www.dictionary.com an animal is defined as.

1. A multicellular organism of the kingdom Animalia, differing from plants in certain typical characteristics such as capacity for locomotion, nonphotosynthetic metabolism, pronounced response to stimuli, restricted growth, and fixed bodily structure.
2. An animal organism other than a human, especially a mammal.
3. A person who behaves in a bestial or brutish manner.
4. A human considered with respect to his or her physical, as opposed to spiritual, nature.
5. A person having a specified aptitude or set of interests: “that rarest of musical animals, an instrumentalist who is as comfortable on a podium with a stick as he is playing his instrument” (Lon Tuck).

Corals as far as I know do not have any form of locomotion especially SPS and LPS. Some soft corals can move by them selfs. Corals are also almost all photosynthetic. Corals also for the most part do not have a restricted growth or fixed body structure. This rules them out of the animal category completely.

Anemones are the closest to animals because they can move, have a restricted growth, and fixed structure. But they are still photosynthetic making them not animals.

 

If you take away the light they will die. They can not live without light. The algae that live inside of them is part of them. To say it it a symbolic relationship is just non since. Thats like saying that we have a symbolic relationship with are white blood cells. Without are white blood cells we would get sick and die.

So with that in mind they are photosynthetic.

Besides even if they are not photosynthetic they still have no form of locomotion, they keep growing, and they do not have any set shape.

We should call them plants because plants have no form of locomotion, they keep growing, they do not have any set shape, and they are photosynthetic.

Why are they animals?

Because when they spawn the eggs and sperm create a zygote (fertilized egg). Zygotes develop into a oval planula larval that hatches and swims. Planula larval is defiantly an animal. It can swim (locomotion), has restricted growth (does not grow much if any), has fixed body shape, and is non photosynthetic. Planula larval will settle down on a solid surface and then metamorphose into a polyp. Once one polyp is established it will continue to grow (LPS, softies) or asexually reproduce into more polyps (SPS).

Something I was not thinking about before was that a coral is a colony of polyps. Polyps are restricted to growth, and do have a fixed shape. The colony itself is not restricted in size or shape.

In summery corals are only animals because of how they start out in life. otherwise they would not be an animal.

Please correct me if I am wrong about this in any way.

To say it it a symbolic relationship is just non since.

Why is it nonsense?  Is that corn field across the street part of you?  Without photosynthesis you would most certainly not exist.  Just 'cause some corals keep their farms inside their bodies doesn't mean they're plants.

In summery corals are only animals because of how they start out in life. otherwise they would not be an animal.

No.

A multicellular organism of the kingdom Animalia, differing from plants in certain typical characteristics such as capacity for locomotion, nonphotosynthetic metabolism, pronounced response to stimuli, restricted growth, and fixed bodily structure.

They are in the kingdom Animalia.  Some exhibit locomotion, some don't.  They are all nonphotosynthetic, they respond to stimuli, they show restricted growth and have a fixed body structure.  Maybe that definition isn't right

I really like this thread! I'm learning alot!

No I don't think there are any animals with chloroplast genes on their genomes. The chloroplasts housed by those mollusks cannot proliferate because, while the chloroplast has many of the genes it needs to build more chloroplasts, many more required genes are on the host genome. So... it is symbiosis.

Wow, deedo.. Excellent posts

It is a mutualistic sybiosis because the zooxanthallae and coral help each other. You have ancient sybionts in most cells of your body too, with their own DNA and everything.

Coral can either get their first zooxanthalae from eating it:

http://www.biolbull.org/cgi/content/abstract/196/1/70?maxtos how=&HITS=&hits=&RESULTFORMAT=&fulltext=zoox anthellae+planulae&andorexactfulltext=and&searchid=1 125797406707_41&stored_search=&FIRSTINDEX=0&reso urcetype=1

Or zooxanthallae can be implanted directly into the egg before fertilization:

http://www.biolbull.org/cgi/content/abstract/205/1/66?maxtos how=&HITS=&hits=&RESULTFORMAT=&fulltext=zoox anthellae+planulae&andorexactfulltext=and&searchid=1 125797406707_41&stored_search=&FIRSTINDEX=0&reso urcetype=1

 

Edited by deedo

Classification of Acropora sp.

Kingdom - Animalia (includes all animals)

Phylum - Cnidaria (includes all cnidarians - ie jelly fish, anemones, corals, hydras etc..)

Class - Anthozoa (includes all corals and anemones)

Order - Scleractinia (includes all stony corals)

Family - Acroporidae

Genus - Acropora

Species (ie palmata)

Coral are animals that are able to "catch" zooxanthellae.  These zooxanthellae are dinoflagellates of the genus symbiodinium.  These were originally believed to be animals hence the name "zoo"-xanthellae.  These symbionts are captured the same way other food sources are except the symbiodinium is not digested but stored within the coral tissue where they grow and their metabolic waste feeds the corals.  Some corals such as Dendronepthya do not contain zooxanthellae in their tissue but consume them directly.  In response to corals not moving I think that is important to mention pulsing xenia and the ability of fungia to move by hydration and pivoting.  For people who think that plants don't move check out the BBC produced "Secret lives of plants".  Also their is much debate whether or not dinoflagellates are animals or algae.  Algae on the other hand is in the Protista kingdom so technically zooxanthallae is neither plant or animal but algae.  Truth be told algae is just as fascinating as corals plus they taste alot better


Edited by davehuish