Hello fellow pearl people!
Recently, Steve Metzler contacted me and put me in touch with Ana Vasilu who is doing research on shell formation at the University of Granada in Spain. We have been corresponding and I have sent samples of shell anomalies to Ana Via Steve. It has caused me to write down some ideas that I have been mulling over. For a few years I have been speculating about the nature of pearl formation in at least some species of haliotis. It's been a matter of putting together some of what I have read about haliotis with observations I have made and speculating as to what this might mean. This applies only to the smaller, more-round or nugget-shaped, free pearls found, to my knowledge, in the area of the mantle in abalones. I have now formed an hypothesis based on these speculations. I have between little and no proof of what I propose in the following, but think that my ideas are quite possibly worthy of serious, scientific investigation. Therefore--I propose the following:
1. Haliotis, or abalone seem to have very prodigious shell making capacities. It seems to me, for a couple of reasons, that they are able to produce and lay down a lot of shell very quickly both to keep ahead of the many parasites that are constantly riddling and eating away at their shells, and also they both need and have the ability to repair very quickly, punctures and other traumatic shell damage.
2. Along with an ability to produce nacre quickly (I assume) they are also able (again, I assume from my observations) to very quickly produce the protein-based component of their shells--conchiolin--in large quantities. To my limited knowledge, it seems there is no other type of mollusk that has such a prodigious ability. I also assume that there must be an evolutionarily advantageous reason for this.
3. Abalone are hemophiliac. Therefore, it is of primary importance for them to protect themselves from damage or intrusion by predators or parasites that would cause them injury and thus cause them to bleed to death. If such predators or parasites intrude through their shell in such a way that they might cut or other wise do injury to the abalone, then, in evolutionary terms, the survivors would likely be those that had an effective mechanism of defense. I propose that the parasitic invader most likely to cause the need for such defense may well have been one or more of the boring clams or something very like them. In order to bore through the shell of the abalone, the clam has rough, abrasive projections on the outside of it's shell that, when rotated back and forth, wear away at the abalone shell. I assume that the boring clams that parasitize the abalone are not focusing on abalone specifically. I have seen the bore holes of boring clams in a number of materials including wood and even soft sandstone or mud stone. They tend to bore up to several inches into the material. I propose that when the clam finally breaks through to the inside of the abalone shell, it maintains it's attempt to bore and thus, by it's boring action, or even simply by presenting a rough, abrasive surface to the body of the abalone, threatens to cut or abrade the abalone, therefore threatening it's life. It is possible that the survivors had the ability to produce large quantities of conchiolin, which I have read of as being essentially a glue composed of several proteins. After cleaning out several hundred blister pearls, I feel very confident stating that every one of these blisters, where the clam shell is still in place, or even most of them where the clam's shell is missing, and where the mollusk has had time to react to the damage, contains, inside of the blister, a very heavy layer of conchiolin that can be up to two millimeters or more in thickness. The conchiolin usually extends down the sides of the clam shell, effectively, I think, cementing it in place. When it is finished depositing the conchiolin, the abalone will then cover the conchiolin with layers of nacre and more conchiolin, thus walling off the clam.
4. I propose that this very-powerful defense-mechanism, which is capable of producing large amounts of shell material very quickly to protect the mollusk from life-threatening injury, is constantly in a state of high alert and easily set in motion, possibly even by stimuli other than it's intended target. There is a parallel hypothesis that might serve as a model, for which there is a growing body of evidence I understand, in the allergic or histamine response in mammals--including humans, of course. Apparently the histamine system has evolved to defend against parasites larger than bacteria, viruses or fungus. It has been proposed that this high-powered defense-system may often be triggered by stimuli other than parasites and that is the cause of our reacting allergically to normally harmless substances. Like allergies, I think it possible that the shell building mechanism of the abalone is often set in motion other than by trauma or alternatively, by trauma other than that which this system could defend against and that this stimulates the mollusk to produce separate, individual, or even clustered pearls.
5. I have read statements by so-called experts on haliotis pearls, that a pearl is produced by an abalone only once in many thousands of cases. My experience is that this is simply not true. I have found, and presently possess between 30 and 40 abalone pearls and I have gone through less than one thousand shells--quite a few less, to be sure--perhaps as few as a couple of hundred. Every one has been found attached to or even completely embedded in, abalone shells. Usually when I have found them, there have been more than one, often several, usually clustered together in close proximity. This leads me to believe that abalones are much greater producers of pearls than is generally thought.
6. I tend to think that these pearls, which, from their placement, seem to me to come from the mantle, are produced away from the shell surface until a point in time when they are, for unknown reasons, released from the tissues where they are formed. I propose that most likely, most of these pearls simply drop out of the shell and are "lost" on the sea floor. I also propose that the conditions under which the pearls become attached to the inside of the shell require special circumstances. These circumstances would probably be a combination of A. the abalone being at rest; and B. that it be during a period when the abalone is actively producing either conchiolin or nacre, thus creating conditions by which the pearls might be attached firmly to the shell and thus not drop out when the creature is in motion. The abalones then continue to lay down layers of shell on and over these pearls, sometimes embedding them in the shell entirely, until the creature dies.
7. Should my proposal prove true, then most of the pearls produced by the abalones in the wild are never found. It is possible that a wealth of abalone pearls are not being harvested. In a world in which natural pearls are becoming vanishingly scarce, it would seem valuable to me to find some way to recover these pearls before they are lost or destroyed through natural processes on the sea floor.
8. This might depend on the abalone's behavior patterns. I know little of this, but have read that haliotis may stay within a territory or live or at least rest in a specific place for most or much of it's lifetime. If this proves true, then it might be possible to recover the pearls that an abalone produces and subsequently drops by searching, perhaps by sieving or by a vacuuming process, appropriate substrates in it's territory. If true, then an abalone might, possibly, then be of more value alive and living free then dead and harvested. This could be a tremendous boon to threatened abalone populations.
9. Governmental bodies might then develop systems giving rights to the abalone pearls within specific territories or even to specific abalones to individuals or groups who then, to guard their source of pearls, would become protectors of these abalones.
I have thought this over for several years and think that it is a plausible hypothesis and worthy of investigation. Other than biochemical and/or structural analysis, to discern the processes by which they form, I think that the next place to investigate would be commercial abalone farming enterprises such as are found in New Zealand. If a way could be found to retain any of these pearls then that might establish that at least some haliotis species do produce and drop free pearls. It might provide a boon to the growers as well.
My only goal in this is the protection and possible restoration of the remaining abalone populations. I do not and have not harvested live abalone and have no interest or part in any venture to harvest abalone or their pearls. All of the shells I have acquired have, to my knowledge, been long dead and were taken long before it was perceived that there was a crisis in haliotis populations. Most of them were attained from sources a long way from any place where they could have been harvested. In fact, a good many of them come from the mid-western US.
Let me know what you think.