natural or synthetic nuclei?

[GemGeek]

If a parasite drags some epithelial cells along with it, they will secrete nacre. Munch munch, chomp chomp, ptooi - voila - a pearl!

 

[Pearl Dreams]

Wow Pearl Dreams, I forgot that important point, the oyster has to "feel" the intruder to trigger the production of nacre!

But there is a difference between sensory receptors detecting a harmful force and reflexly triggering a protective reaction, and the mussel or oyster consciously feeling pain.
I don't think they "feel" the same way we feel, because they don't have consciousness.

If a parasite drags some epithelial cells along with it, they will secrete nacre. Munch munch, chomp chomp, ptooi - voila - a pearl!

Yes, I've read about that-- but the question remains, what purpose does the secretion of nacre serve in this case? Seems logical that it might be to coat the intruder- maybe to neutralize the threat of a living parasite, if not to reduce irritation?

 

[Lagoon Island Pearls]

Yes, I've read about that-- but the question remains, what purpose does the secretion of nacre serve in this case? Seems logical that it might be to coat the intruder- maybe to neutralize the threat of a living parasite, if not to reduce irritation?

In the case of extrapallial pearls, it's merely a coincidence. If you stand between a paint sprayer and a wall, you'll get painted to the wall. Many of the parasites bore through the shell into the extrapallial space. While there may be some subsequent irritation, the outer epithelial layer was aready producing nacre, not triggered to begin producing it.

It's important to remember, that epithelial cells to not grow spontaneously out of the blue. They only grow by dividing and multiplying and occupying the adjacent space.

In tissue grafted pearls, epithelial cells from the donor grow to produce the pearl, NOT the epithelial cells from the host.

The term "irritant" is only applicable in a minority case of natural pearl formations. It's a myth to suggest an irritant is the rule, when in reality, it's only an exception.

 

[Lagoon Island Pearls]

If a parasite drags some epithelial cells along with it, they will secrete nacre. Munch munch, chomp chomp, ptooi - voila - a pearl!

As you know, when you open a shell you kill the animal, however the epithelial cells continue to live for a period of time. It is possible that a parasite (or other trauma) can displace epithelial cells which may form a pearl sac. It's also been described that parasites themselves my die within the tissues and their mantles pick up the vascular supply of the host and the cells continue to divide and multiply. These are examples of homogeneic and xenogeneic pearls.

 

[Cyril Roger Brossard]

In the case of extrapallial pearls, it's merely a coincidence. If you stand between a paint sprayer and a wall, you'll get painted to the wall. Many of the parasites bore through the shell into the extrapallial space. While there may be some subsequent irritation, the outer epithelial layer was aready producing nacre, not triggered to begin producing it.

It's important to remember, that epithelial cells to not grow spontaneously out of the blue. They only grow by dividing and multiplying and occupying the adjacent space.

In tissue grafted pearls, epithelial cells from the donor grow to produce the pearl, NOT the epithelial cells from the host.

The term "irritant" is only applicable in a minority case of natural pearl formations. It's a myth to suggest an irritant is the rule, when in reality, it's only an exception.

Exactly!
Also you must define 'parasitism' (since the term is coined here).
if you are referring to species such as Pinnotheridae, then this is not parasitism...

 

[Cyril Roger Brossard]

That's a serious question. I'm no specialist in that area either, but it always comes up in the differential diagnosis. In the absence evidence by instrumentation, I take a lot of guesses. It usually comes into question during the septic/aseptic discussion. The ratio of non-sterile to sterile is definitely higher in extrapallial pearls. Even in cases of spontaneously formed, sterile, auto-immune pearls an environmental factor may be implicated. I find it safer to stick to "multiple etiological factors".

Whether something beneficial is aquired while a mollusk is otherwise under a environmental stress will always remain a valid question. I've certainly seen a few cases where invasive species were highly beneficial. (though I'm speaking biomass as opposed to a single specimen) Yet any mollusk in the absence of pearls or other malady are remarkably self-regulatory but greatly influenced by lunar cycles (tides/quiescence) and seasonal temperatures. Those would be major environmental factors affecting internal mechanisms.

It doesn't take much to induce mollusks to spawn. At least not around here, anyway. Often, simply putting them back in the water after transport has them giving up the gametes. Sinking them in water 10 degrees colder will too, though that might be hard in the tropics.

I wouldn't dismiss pheromones (sp) on reproductivity, but don't see much of a connection to shell building or pearls.

I'm a little over my head myself on the topic too.

Well food for thought:

until recently it was assumed by academics that hormones were the result of an endogenous biosynthesis as you probably suggested in your previous post.
this said a recent study as underlined that there is no convincing evidence for biosynthesis of vertebrate steroids by mollusks, hence the provenance of those hormones were actually exogenous of origin, it was further shown that there is very strong evidence that mollusks are able to absorb vertebrate steroids from the environment; and are able to store some of them (by conjugating them to fatty acids) for weeks to months. It was made notable that the steroids that have been proposed as functional hormones in mollusks (progesterone, testosterone...) are the same as those of humans. Since humans (and indeed all vertebrates) continuously excrete steroids not just via urine and feces, but via their body surface (and, in fish, via the gills), it is impossible to rule out contamination as the sole reason for the presence of vertebrate steroids in mollusks.

I was interested in your point of view as it is always important to challenge what we think we know... Evolution in technology allows us to see now that what we knew right yesterday may actually be wrong tomorrow.

 

[Caitlin]

Strack's definition is in line with Gem Geek's. A pearl can form whenever epithelial tissue gets inside the mantle for what ever reason- a fish bite maybe.

It is not the irritation that causes the nacre production, it is the mechanical fact of however the mantle edge cells get inside the body. Not knowing where they are, they keep producing nacre because that is what they do. Blister pearls form directly on the shell as it is the epithelial tissues that create the mother of pearl in the shell. if there is a bump in the shell, for any reason, it gets coated as though it were the shell.

 

[Caitlin]

Wow Pearl Dreams, I forgot that important point, the oyster has to "feel" the intruder to trigger the production of nacre!

No. Irritation does not cause the nacre production, the epithelial cells do that, regardless. When something else carries a few epithelial cells into the body of the mantle, they keep growing nacre as that is their job, where ever they are in the pearl.

so, everyone, drop the word, "irritation". It is a word that anthropomorphizes the mollusk. Irritation is inflammation and mollusks do not use inflammation to create pearls. I don't think they even have inflammations. They have mindless cells that produce nacre, whereever they end up in any body part of the mollusk. That is why the bead in the gonad with some skin cells can grow a pearl. It is not the bead that causes pearl formation, it is the skin cells put in there with it.

 

[DerekJ]

I always thought there was the possibility that the mantle tissue from a parasite/predator could cause nucleation. I've always wondered why some mollusc's could produce different coloured pearls when their shell only has one colour. From example, I have a light brown tridacna pearl, but I haven't never seen a brown tridacna shell.

 

[Caitlin]

Parasites and predators have become nuclei of some pearls, but only if the mollusk's epiithelial cells get under the skin with the object. Gem Geek's link today showed an entire seashell inside a natural pearl. Objects inside natural pearls are actually quite rare, though they can be varied -Everything BUT a grain of sand!

 

[DerekJ]

I read that Gems and gemmology article when I was in Tucson. That photo was in Ken's powerpoint when they were showing how 3D xray radiography could be used to examine nuclei instead of sawing a pearl in half.

 

[Lagoon Island Pearls]

Everything BUT a grain of sand!

Any foreign body in the extrapallial space gets stuck to the shell like anything else. Clay Buddahs, your car keys, fish, snails... and yes... sand.

Sand pasted to the shell is really common in scallops. It's because they migrate by repeatedly digging and swimming their way around. I have also observed sand nucleated pearls in barnacles, geoducks, jingles, moon snails and mussels. In almost every instance, broken or cracked shells are implicated or parasites created enough of a lesion that causes sand to be lodged in tiny cuts or in a place where mucous cannot gather it to be expelled.

I use acid to dissolve nacre, which dislodges the sand for analysis.

As I commented on the "irritation" thing, sand as a nucleus is the exception, not the rule.

 

[Cyril Roger Brossard]

Any foreign body in the extrapallial space gets stuck to the shell like anything else. Clay Buddahs, your car keys, fish, snails... and yes... sand.

Sand pasted to the shell is really common in scallops. It's because they migrate by repeatedly digging and swimming their way around. I have also observed sand nucleated pearls in barnacles, geoducks, jingles, moon snails and mussels. In almost every instance, broken or cracked shells are implicated or parasites created enough of a lesion that causes sand to be lodged in tiny cuts or in a place where mucous cannot gather it to be expelled.

I use acid to dissolve nacre, which dislodges the sand for analysis.

As I commented on the "irritation" thing, sand as a nucleus is the exception, not the rule.

couldn't agree more with dave. this said sand is not limited to quartz, be reminded that depending on your geographical location sand could be a particle of calcium carbonate such as aragonite of about 62 micron to 2mm of diameter

 

[Caitlin]

Any foreign body in the extrapallial space gets stuck to the shell like anything else. Clay Buddahs, your car keys, fish, snails... and yes... sand.

Sand pasted to the shell is really common in scallops. It's because they migrate by repeatedly digging and swimming their way around. I have also observed sand nucleated pearls in barnacles, geoducks, jingles, moon snails and mussels. In almost every instance, broken or cracked shells are implicated or parasites created enough of a lesion that causes sand to be lodged in tiny cuts or in a place where mucous cannot gather it to be expelled.

I use acid to dissolve nacre, which dislodges the sand for analysis.

As I commented on the "irritation" thing, sand as a nucleus is the exception, not the rule.

How often are the pinctadas afflicted with sand pearls? You only mentioned mussels. In any case, if there is a cut and epithelial cells get carried inside the body with sand, the pearls can have sand nuclei? How many or what percent of pearls have sand nuclei? I only want to know about the popular pearls people can buy. How often is sand pasted to shells in the pinctadas? I don't care about scallops. Or all your other exceptions. That may be technically true, but it is on an advanced level of interest.

What are the odds for a pinctada to get sand glued to their shells or end up as a nucleus? Have you ever seen it or heard of it? Why keep that myth alive, even if you are referring to odd mollusks that never go on the market, the lines at a site like this get blurry unless you compare and contrast with pinctadas and maybe pteria sternas. You said scallops get sand glued to their shells? That means no other mollusks have that trait? Does saying that it prove a point about the kind of pearls people buy? Or just the rare pearl you deal with?

I always thought people had to secure the lead buddha to the inside of the shell to keep in place. Maybe a discussion of how mabes are cultured would be enlightening.

 

[Cyril Roger Brossard]

Caitlin, based on my modest experience with Pinctada maxima, I have, in a few rare occasions, seen non-seeded shells bearing minute pearls, ipso facto not a by-product from seeding operation (verified and confirmed). True those are rare, I recollect less than 3 cases over a period of 15 years equivalent to a few million shells, this said they do exist, they are small and are usually (but not limited to) found within the epithelial tissues of the paleal cavity.
I know that one found in similar circumstances was recently sent to GIA for analysis.
Sand in the Philippines is mostly aragonite. What will be seen under microscopy is unknown so far, I do not know if anything at all will be left as 'sand' is quite small (2mm max diameter) and aragonite crystal may fuse together.
I do not know for other species but since you mentioned Pinctada specifically, please accept the above as my contribution.

Oh in term of percentage that would be less than 0.0001%...

 

[Lagoon Island Pearls]

be reminded that depending on your geographical location sand could be a particle of calcium carbonate such as aragonite of about 62 micron to 2mm of diameter

Agreed. Especially in areas where mussel shells disintegrate downward to gravity or clam shells that move upward by wave action. Some wind exposed beaches have no sand at all, just shells or other detritus.

 

[Caitlin]

Thanks
I can easily see some epidermis cells breaking away from the edge, but staying in the shell. Too bad it happens so rarely. But is there sand in them? even calcium carbonate sand?

 

[Lagoon Island Pearls]

How often are the pinctadas afflicted with sand pearls? You only mentioned mussels.

We don't have Pinctada sp. in Canada. I have yet to see evidence that species form shells any differently than any other mollusk. In the absence of certain specimens, the use of analogs is a widely accepted practice.

In any case, if there is a cut and epithelial cells get carried inside the body with sand, the pearls can have sand nuclei? How many or what percent of pearls have sand nuclei?

You are completely missing the point. I have been very careful to specify "extrapallial" pearls only, meaning the space BETWEEN the outer epithelial layer and the shell lining. Nothing more.

Most pearl oysters are suspended above the sediments most of their lives, so the chances of picking up and retaining sand is negligible.

I only want to know about the popular pearls people can buy. How often is sand pasted to shells in the pinctadas? I don't care about scallops. Or all your other exceptions. What are the odds for a pinctada to get sand glued to their shells or end up as a nucleus? Have you ever seen it or heard of it?

Sorry for discussing pearls that don't go to market. My bad.

Why keep that myth alive?

I went to great lengths to debunk it. Instead, my work confirmed it.

You said scallops get sand glued to their shells? That means no other mollusks have that trait? Does saying that it prove a point about the kind of pearls people buy? Or just the rare pearl you deal with?

Scallops have a higher incidence, because of their behavior, but when it comes to their pearl's formation themselves, the SAME rules apply.

even if you are referring to odd mollusks that never go on the market, the lines at a site like this get blurry unless you compare and contrast with pinctadas and maybe pteria sternas.

I have no access to those species.

I am unable to comply with that rule so I suppose my time is done here.

 

[Cyril Roger Brossard]

Thanks
I can easily see some epidermis cells breaking away from the edge, but staying in the shell. Too bad it happens so rarely. But is there sand in them? even calcium carbonate sand?

I personally observed presence of mud, aglaophenia, developing bryozoans and even silt and sand (silt is smaller in diameter than sand) within the first inches (lips) of weakened shells, at that stage the metabolism is quite low, fecal matter limited mainly because intake is limited. During recovery a new layer of nacre would cover the affected area and eventually cause what we described as double-lips. The shell doesn't remain close for long periods, the shell would open for longer periods and would be slow to close, this would in some cases be concluded by death caused by predators (death by blennies...)
You must know all of the above, but considering those points, it must be possible for exogenous particles to enter the shell during this weakened stage.
Again death isn't a must, and recovery was observed on several occasions. Recovery being here the result of attentive care from the farmers.
Sorry for not being able to post pictures or more details.
Hope this helps a bit.

 

[Caitlin]

I have no access to those species.

I am unable to comply with that rule so I suppose my time is done here.

Oh Dave!! I am so sorry. I sent you a PM first, but I have to let you know I was asking for myself only, not as an admin!

I knew you often commented on natural pinctada pearls here. I thought you did know. I now discern a bit of a prickly tone in my post, but I was actually very scared about a situation that developed in my own life. I let a bit of emotion leak through.

I am so sorry.....