Age of anemone

[gramma royale]

Hi all,

I read somewhere that anemones can literally live forever. I find this hard to believe. What sort of evidence is this based on? How can you determine that an organism is immortal? And lastly, how do you tell the age of an anemone?

Thanks

[rshimek]

Originally posted by gramma royale

Hi,

I read somewhere that anemones can literally live forever. I find this hard to believe.

Too bad. :D You better get used to the idea. Cnidarian polyps, in general, as well as several other groups of animals such as echinoderms and some mollusks and flatworms, have no old age or senesence. They quite literally do not age, and have a potential life span that is unending. In reality, something will always get them eventually, but the potential is there.

What sort of evidence is this based on? How can you determine that an organism is immortal?

Several kinds of evidence, mostly ecological. The population is examined for differences in morphology, etc., that are related to age. Generally for animals that die of old age there is a period of post-reproductive decline followed by death (as in people; Pacific Ocean salmonid fishes; hydrozoan jellyfish; some annelid worms). This type of change is noticeable, and additionally there is a finite mortality rate that can be measured. For these "immortal" animals, none of these changes can be found.

Additionally, one can make the assumption that a natural population is more-or-less stable in size. If this is the case, the number of juveniles recruiting into the population must equal the number of adults dying. In many anemone populations, the number of recruits is essentially zero; indicating that either the population is crashing or that once the animals reach adulthood they live very long times.

As an example of this process, I worked on a particular anemone in the NE Pacific called Cribrinopsis fernaldi. I did maybe 500 dives over a ten year period, dedicated to looking at or for these animals. I found lots of adults; hundreds to thousands maybe. I found 2 juveniles. As near as I could tell, the animal's population was stable. Additionally, for this species in this area, I determined that it caught and ate swimming scallops. When it was done eating, it would burp out the scallop shells and they would collect around the base of the rocks the anemones sat on. The anemones didn't move once they had found a rock and in some places the rocks had a 4 to 5 food deep layer of scallop shells around them - all from the one anemone eating. Doing some "back of the envelope" type of calculations based on feeding rate, and the rate of decomposition of scallop shells, it appeared those anemones had been sitting on their rocks eating scallops for 300 to 500 years.

Other people have examined the growth rate of this species in the laboratory and came to about the same age estimate for adults.

Similar results have been found for other anemones, including bye the bye, Pacific Ocean Host sea anemones...

So...they appear to have the ability to live for a very long time.

And lastly, how do you tell the age of an anemone?

You really can't as they have no hard parts, but you can look at some closely related animals and get an indication of age. Stony corals are essentially anemones that live in skeleton of their secretion. Massive corals, such as Porites growing in reefs away from the equator (where there are defined growth seasons) lay down bands of skeleton that are dense (in the winter due to slow growth) or less dense (in the summer due to fast growth). If one takes a hollow drill and cores the colony, one may then count the growth rings just as in trees (generally by x-raying the skeletal coring, but there are other means as well). The oldest colony that I have seen data for was over 7,500 years old, and was healthy and growing. So some corals at least (most actually, probably), have the potential of being around a long time.

Anemones are assumed to have the same potential life span.

Some 30 or so years ago, one of the common intertidal clonal anemones in the Pacific NW was studied, and the person studying them examined a large number of colonies over several years for juvenile recruitment from sexual reproduction. He then made the assumption that you could say if you looked at a lot of area for a short time, it was analagous to looking at a small area for a long time (now there are problems with this, but in general, it is at least a start for understanding population dynamics). He found very, very low juvenile recruitment and death rates in established populations, and good recruitment in vacant areas (he created the vacant areas). He was convinced - but could not prove it - that those anemones on at least some of the the beach rocks had occupied the rocks as soon as the glaciers retreated off the rocks about 9,500 years ago and that the clones and perhaps the same anemones had been there ever since.

Finally, in some laboratories anemones have been kept as "mascots" or pets for very long times. The longest that I know of was one that was kept for over 90 years, and it was a small individual and during that time did not appreaciably grow.

In general, the concensus is that anemones can live essentially forever... and so can sea stars.. clams.... big bristle worms...

:D

[Flame*Angel]

Immortality is hard to conceive. Wow. This is very humbling.

[wizardgus®]

Which gives rise to yet another reefkeepers worry...who'll look after my corals when I die?

[gramma royale]

Thanks Dr :)

This is indeed a humbling notion. I told several of my friends about this and they can't believe it either. I think a couple of them actually took offense to the idea :rolleyes: >sigh< .

BTW, I was planning to set up an anemone only tank. I was planning to keep one Stichodactyla anemone, but I'm not sure which one. The tank is 18 gallons and will have a 5" sandbed. I will be using only one small piece of live rock, 4"x4"x4" at most. Would you be able to suggest a particular species that would do well in this particular tank?

[rshimek]

Hi,

Sorry, I can't suggest any anemone that would do well for a reasonable period in a tank that is that small. It is far too small for the host Stichodactyla species.

[gramma royale]

Drat. How large a tank does a Stichodactyla anemone need to feel comfortable in?

[rshimek]

Hi,

These are large animals, if adequately fed all the host carpet anemones can easily reach diameters of 18 inches or more, and the column alone can be more than a foot across. In addition to their physical space requirements, are also the requirement for filtration, etc. It is very hard to have an adequate biological filter for such a large animal in a small tank.

I would not advise keeping one of these animals in a tank much smaller than about 50 gallons.

:D

[gramma royale]

Cool, thanks for the info. I just recently got a 100 gallon tank, but set it up as a Tanganyikan cichid tank. But it looks like my friend's looking to sell his 125, so maybe I'll get the chance to set up species tank :)

[Harpo]

Hi Dr. Shimek
How about Stichodactyl tapetum for a small tank? Mine only grow to about 2.5 cm.
Mark

[Mike_Noren]

Originally posted by rshimek
Hi,

Sorry, I can't suggest any anemone that would do well for a reasonable period in a tank that is that small.

Hmm... How about Condylactis passiflora? Or perhaps even something like Anemonia majano?

[rshimek]

Hi Mike,

Yes, I should have qualified my answer. :eek2: There are many species of small anemones that will do well in a small tank, but none of the host Indo-Pacific Anemones will do so for any prolonged period, they are just capable of becoming too large.

[PoggiPJ]

Dr. Ron,
Are there any small species that would host a clown fish?

[rshimek]

Hi Pete,

No. The clown may take them as a host, but if they do, they will literally buffet the anemone so much that it cannot feed or open normally and it will eventually (and in not too long a period) die.

:frog: