MarineBioHSU
In Memoriam
Ok folks, so I am starting this thread with the hopes that we can as a community try and uncover and quantify what factors initiate reproduction in anemones in our aquariums, both sexual and asexual. Obviously, a good place to start is to understand what factors initiate reproduction events in the wild, and try and correlate this to captivity.
I am currently involved in farming E. quadricolor via manual division, and while I think that almost any species of anemone can undergo transvers fission and survive, I do not feel that at this point, it is the best method of farming these guys in captivity. Instead, I feel we should strive to lean how to consistently stimulate spawning in captivity. There are numerous accounts of captive spawning occuring, albeit unintended by most aquarists, however it is an encouraging sign that it is possible. Additionally, Anna Scott has done a fair amount of research into sexual reproduction of several host anemone species in captiviy, apparently with a fair amount if success.
So, it seems like one of the primary points of interest/contention is what exactly causes anemones (namely E. quadricolor) to reproduce via transverse fission.
There are numerous reports of this happening in captivity, and many of the reports seem contradictory.
One of the general ideas posed by biology is that, in general, a species will reproduce via asexual means when conditions are suitable enough that no exchange of gametes are necessary. Where-as sexual reproduction would then be stimulated by a stressful event that would necessitate a mixing of genetic material, either to deal with a reduced genetic pool, or perhaps to produce encysted offspring that can withstand a period of toxicity.
At first glance this would seem to indicate that BTA's for example, would be dividing in our tanks as a result of favorable conditions, such as enough food etc. It does seem to make sense that the anemones could be "thinking" that if their genotype is suitable to their environment, there is no reason to alter things. One piece of evidence that seems to support this are the numerous reports from aquarists that feeding their anemones heavily for a week or so will result in a splitting event.
HOWEVER, at the very same time many aquarists feel that their anemones split as a result of stress, for example some folks notice a large water change, power outage etc can stimulate a division. Furthermore, some aquarists feel that "overfeeding" can stress anemones into dividing, which seems like it may not make a lot of sense. However, again it has been so well documented in captivity that there is clearly some merit.
And perhaps most interesting of all, many aquarists that are successful with anemones have very different experiences, what I mean is some times a well fed BTA may continue to grow and grow and never divide, where-as another well fed and happy anemone will divide like no other! To me this would indicate that there are other factors coming into play.
So, in light of the above evidence I would like to examine what benefits and drawbacks there are to different methods of reproduction for anemones.
1. Asexual reproduction: By and large all the anemones that we keep in captivity that can/do reproduce asexually undergo transverse fission, that is they divide through the mouth, however there are reports of budding and intratentacle polpys being formed as well.
Again, standard biological wisdom would seem to indicate this method of reproduction would occur during times of plenty. However several studies have indicated there could be other factors. For example, perhaps the anemones divide as a means of tissue regeneration, which theoretically could explain division from "overfeeding"....maybe after digesting food the anemone "feels" a need to re-grow GVC tissues that were utilized, and division is a good method to speed this up?
Furthermore, several studies have shown a positive inverse correlation between feeding and division rates, that is to say, in the experiements, anemones that were not fed divided frequently, where-as anemones that were fed often did not divide. This would seem to contradict many of the observations from hobbyists, myself included.
An additional study done on the east coast of North America showed that anemones in higher water flow divided more rapidly thatn those found in lower flow situations, and this would seem to refelct the conventional idea held that smaller colonial BTA's are found in shallow waters and larger individual specimens tend to occur in deeper waters.
So to try and sum up asexual division:
1. Some evidence suggests asexual division may occur as a result of preserving genotypes that are suited to current conditions.
The idea behind this theory is that if the anemones are doing well in their environment, then there is no reason to change so to speak, in other words if it aint broke dont fix it. This could explain why anemones in shallow water/high flow situations divide more often, more food being swept into their tentacles/more light etc. This would of course explain the observations that increased feeding induces splitting in some captive anemones.
2. Some evidence suggests that asexual division may occur as a means of growth/tissue regeneration.
This theory proposes that old tissue can be shed via division, the net result being two individuals with a significant amount of new tissue/growth. Since anemones have no know life span and indeterminate growth, this theory makes sense.
This theory may be harder to test in captivity, but not impossible. I propose that anemones under higher lighting situations may need to divide more frequently for tissue regeneration as a means of dealing with free radicals resulting from UV light/photosynthesis etc.
3. Some evidence suggests that asexual divison may occur as a last ditch effort to preserve an individuals genotype when faced with degrading conditions.
This theory could explain why anemones may divide under stressful situations. Say for example that conditions are rapidly becoming unfavorable, and the anemone does not have time to release gametes, its best option would be to try and divide rapidly to give its individual genotype the best chance of survival.
There are a few problems I see with this theory:
1. Many studies have shown that most anemones almost constantly have mature gametes present in their mesentaries.
2. Additionally, a spawning event would produce a far greater amount of offspring, therefore a greater chance of survival, in addition to a greater chance that a beneficial mutation could occur that would create a genotype more suited for altering conditions.
3. Numerous observations of known stressful occurences (such as el nino years) on reefs have shown that when faced with such conditions, host anemones tend to expell zoanthellae and maintain themselves via feeding and self absorbtion. So, it would seem like reducing their nutrient reserves through division and the energy required to divide and heal would not be a "wise choice" in unfavorable conditions.
However, there are a few possible explainations for this idea:
1. Some studies have shown that the smaller the diameter of an anemone, the more effective the gain from food capture. So maybe if resources are diminishing, then by dividing, multiple smaller anemones would be able to sustain themselves longer on a single morsel of food than a single large anemone could on the same resources.
At this point it is certainly impossible to make any sort of absolute conclusion, however in light of the evidence, I would suggest that we can start to piece together different scenarios leading to division.
For example, it seems to me that BTA's kept in high light, high flow situations and fed often will divide frequently. Where-as anemones kept in lower light, lower flow situations and still fed frequently may opt to grow instead of divide. Many possibilities.
So, now I am asking everyone here to contribute their ideas/observations. I would also like to come up with a set of parameters to watch/examine that may cause division, or not.
For example, large water changes seem to stimulate division. Perhaps this could be a result of reducing the chemotoxins in the water, thus giving the anemones the impression that there is more room/less competition so they can divide?
Or perhaps a stressful situation such as being left in a bucket or a power outage could cause tissue necrosis, and the anemones response could be to divide, thus ridding itself of the dying tissue and jump starting an immunological response? Again, just my ideas.
This afternoon I will post a list of books/articles/journals etc that I have been reading so that y'all can look for them as well.
I look forward to any and all idea, observations and opinions. I think the knowledge base here is extraordinary and if we can compile and share these ideas in an organzied manner, we can make a lot of progress.
Thanks.
I am currently involved in farming E. quadricolor via manual division, and while I think that almost any species of anemone can undergo transvers fission and survive, I do not feel that at this point, it is the best method of farming these guys in captivity. Instead, I feel we should strive to lean how to consistently stimulate spawning in captivity. There are numerous accounts of captive spawning occuring, albeit unintended by most aquarists, however it is an encouraging sign that it is possible. Additionally, Anna Scott has done a fair amount of research into sexual reproduction of several host anemone species in captiviy, apparently with a fair amount if success.
So, it seems like one of the primary points of interest/contention is what exactly causes anemones (namely E. quadricolor) to reproduce via transverse fission.
There are numerous reports of this happening in captivity, and many of the reports seem contradictory.
One of the general ideas posed by biology is that, in general, a species will reproduce via asexual means when conditions are suitable enough that no exchange of gametes are necessary. Where-as sexual reproduction would then be stimulated by a stressful event that would necessitate a mixing of genetic material, either to deal with a reduced genetic pool, or perhaps to produce encysted offspring that can withstand a period of toxicity.
At first glance this would seem to indicate that BTA's for example, would be dividing in our tanks as a result of favorable conditions, such as enough food etc. It does seem to make sense that the anemones could be "thinking" that if their genotype is suitable to their environment, there is no reason to alter things. One piece of evidence that seems to support this are the numerous reports from aquarists that feeding their anemones heavily for a week or so will result in a splitting event.
HOWEVER, at the very same time many aquarists feel that their anemones split as a result of stress, for example some folks notice a large water change, power outage etc can stimulate a division. Furthermore, some aquarists feel that "overfeeding" can stress anemones into dividing, which seems like it may not make a lot of sense. However, again it has been so well documented in captivity that there is clearly some merit.
And perhaps most interesting of all, many aquarists that are successful with anemones have very different experiences, what I mean is some times a well fed BTA may continue to grow and grow and never divide, where-as another well fed and happy anemone will divide like no other! To me this would indicate that there are other factors coming into play.
So, in light of the above evidence I would like to examine what benefits and drawbacks there are to different methods of reproduction for anemones.
1. Asexual reproduction: By and large all the anemones that we keep in captivity that can/do reproduce asexually undergo transverse fission, that is they divide through the mouth, however there are reports of budding and intratentacle polpys being formed as well.
Again, standard biological wisdom would seem to indicate this method of reproduction would occur during times of plenty. However several studies have indicated there could be other factors. For example, perhaps the anemones divide as a means of tissue regeneration, which theoretically could explain division from "overfeeding"....maybe after digesting food the anemone "feels" a need to re-grow GVC tissues that were utilized, and division is a good method to speed this up?
Furthermore, several studies have shown a positive inverse correlation between feeding and division rates, that is to say, in the experiements, anemones that were not fed divided frequently, where-as anemones that were fed often did not divide. This would seem to contradict many of the observations from hobbyists, myself included.
An additional study done on the east coast of North America showed that anemones in higher water flow divided more rapidly thatn those found in lower flow situations, and this would seem to refelct the conventional idea held that smaller colonial BTA's are found in shallow waters and larger individual specimens tend to occur in deeper waters.
So to try and sum up asexual division:
1. Some evidence suggests asexual division may occur as a result of preserving genotypes that are suited to current conditions.
The idea behind this theory is that if the anemones are doing well in their environment, then there is no reason to change so to speak, in other words if it aint broke dont fix it. This could explain why anemones in shallow water/high flow situations divide more often, more food being swept into their tentacles/more light etc. This would of course explain the observations that increased feeding induces splitting in some captive anemones.
2. Some evidence suggests that asexual division may occur as a means of growth/tissue regeneration.
This theory proposes that old tissue can be shed via division, the net result being two individuals with a significant amount of new tissue/growth. Since anemones have no know life span and indeterminate growth, this theory makes sense.
This theory may be harder to test in captivity, but not impossible. I propose that anemones under higher lighting situations may need to divide more frequently for tissue regeneration as a means of dealing with free radicals resulting from UV light/photosynthesis etc.
3. Some evidence suggests that asexual divison may occur as a last ditch effort to preserve an individuals genotype when faced with degrading conditions.
This theory could explain why anemones may divide under stressful situations. Say for example that conditions are rapidly becoming unfavorable, and the anemone does not have time to release gametes, its best option would be to try and divide rapidly to give its individual genotype the best chance of survival.
There are a few problems I see with this theory:
1. Many studies have shown that most anemones almost constantly have mature gametes present in their mesentaries.
2. Additionally, a spawning event would produce a far greater amount of offspring, therefore a greater chance of survival, in addition to a greater chance that a beneficial mutation could occur that would create a genotype more suited for altering conditions.
3. Numerous observations of known stressful occurences (such as el nino years) on reefs have shown that when faced with such conditions, host anemones tend to expell zoanthellae and maintain themselves via feeding and self absorbtion. So, it would seem like reducing their nutrient reserves through division and the energy required to divide and heal would not be a "wise choice" in unfavorable conditions.
However, there are a few possible explainations for this idea:
1. Some studies have shown that the smaller the diameter of an anemone, the more effective the gain from food capture. So maybe if resources are diminishing, then by dividing, multiple smaller anemones would be able to sustain themselves longer on a single morsel of food than a single large anemone could on the same resources.
At this point it is certainly impossible to make any sort of absolute conclusion, however in light of the evidence, I would suggest that we can start to piece together different scenarios leading to division.
For example, it seems to me that BTA's kept in high light, high flow situations and fed often will divide frequently. Where-as anemones kept in lower light, lower flow situations and still fed frequently may opt to grow instead of divide. Many possibilities.
So, now I am asking everyone here to contribute their ideas/observations. I would also like to come up with a set of parameters to watch/examine that may cause division, or not.
For example, large water changes seem to stimulate division. Perhaps this could be a result of reducing the chemotoxins in the water, thus giving the anemones the impression that there is more room/less competition so they can divide?
Or perhaps a stressful situation such as being left in a bucket or a power outage could cause tissue necrosis, and the anemones response could be to divide, thus ridding itself of the dying tissue and jump starting an immunological response? Again, just my ideas.
This afternoon I will post a list of books/articles/journals etc that I have been reading so that y'all can look for them as well.
I look forward to any and all idea, observations and opinions. I think the knowledge base here is extraordinary and if we can compile and share these ideas in an organzied manner, we can make a lot of progress.
Thanks.
Before I go on and read further, let me guarantee you this is NOT the case. You have experience with one of two clown anemones that asexually reproduce with frequency in the wild. Just because you can cut an E. quadricolor in half and reasonable assume both halves will survive does NOT mean that the said can be said for other species.
