Question about horn shape of abalone pearls

[Isi]

Hi everybody ! Can you help ? I am wondering about the horn shape rather common with abalone pearls, and how and why pearls grow in this peculiar shape.
I quite understand that this horn shape is consistent with the shape of the gonad, as very well shown on a picture of this link :
http://www.abalonepearls.co.nz/about.html
But then I cannot make out precisely what happens when the pearl forms. Is the gonad wrapped in nacre ? Does the pearl come in between the gonad and another organ ? Are these pearls hollow because the organic part of the gonad ends up into disintegrating ?
And, would you say that these pearls are more fragile than others, if they are not made of nacre layers until the core ?
Any opinion welcome, thank you !

 

[SteveM]

This is quite an important question and I hope those with more technical insight will chime in.

Yes, these are from the gonad. Density is an issue as it relates to the overall quality and value of the pearl. But I have never seen a scientific explanation for how nacre develops there, or in the gastro-intestinal tract, given the lack of mantle/epithelial cells. It must be related to extreme physical trauma whereby mantle tissue is somehow introduced.

In pearl culturing, pteriidae (pearl oyster) gonads are targeted for bead insertion due to their convenient shape, but development of a pearl sac capable of forming the inverted shell that we know as a pearl is dependent upon the simultaneous introduction of a piece of mantle tissue as a graft.

 

[Lagoon Island Pearls]

Being gastropods, abalone are highly mobile and agile. They are able to twist, turn and pull with greater ranges of motion than most mollusks. On any given day, abalone can be found in several orientations, whether inverted, sideways or flat. On rough surge or stormy days, they could remain firmly adducted for extended periods.

All of these factors apply pressure to the mucopolysac, hence the resulting formation.

If you were to squeeze a handful of putty, you would end up with three similar shapes between each finger.

 

[GemGeek]

That is very interesting. I was name-dropping monoplacophorans the other day, but you've got me beat with mucopolysac! Cool.

 

[SteveM]

If you were to squeeze a handful of putty, you would end up with three similar shapes between each finger.

That seems too easy…but the abalone/gonad thing must be addressed, as it is pervasive in pearl literature. Just Google 'abalone gonad pearl' for the gonad angle from just about every reliable source. BELOW is the personal experience of Lou Hill ('Mr. Hill' of the Natural Abalone Pearls thread), showing a male Haliotis iris gonad and a similarly-shaped pearl.

Let's get to the bottom of this!! It has ramifications throughout the natural pearl universe, ie are these bezoars or are they pearls? And if bezoars, how are they nacreous?

 

[Lagoon Island Pearls]

That seems too easy? Let's get to the bottom of this!! It has ramifications throughout the natural pearl universe, ie are these bezoars or are they pearls? And if bezoars, how are they nacreous?

Definitely a question worthy of investigation.

I've never found a pearl in our northern abalone, so my submissions to this thread are conjecture at best.

Bezoars tend to be formed from ingested items. Hair, fingernails and other objects (even plastic) are causing agents. While possible, my guess would be... it's unlikely, despite the gonad's close proximity to the GI tract.

It would probably be best to find an abalone pearl "in situ". at this time. In BC, abalone is closed year round for conservation reasons, so I'm unable to offer a bounty for this species.

Rather than making assumptions, I'll ask a few questions instead.

Are the gonads themselves functional, suppressed or reduced in size? Is the gonad affected itself or is the adjacent space filled?
Is diverticulitis or other similar GI disorders observed in abalone?

The photo describes a difference between male/females, but I'm curious to their level of motility or fecundity.

To resolve this, we should probably not get too hung up on the "epithelial tissue donor" concept of pearl culture and look closer at blood acid/base balance, auto-immunity, nerves (ganglion cysts) or parasitation. All difficult science, without living specimens.

 

[SteveM]

Although I haven't yet hit on the perfect source (probably have to pay big bucks to some online science journal), I'm getting the idea from abstracts that the Haliotis gonad does indeed have a digestive as well as reproductive function.

As for the epithelial question, it is the core of the 'gonad dilemma', given abalone horn/tooth pearls' nacreous composition matching that of the inner layer of the shell.

Dealing with some similar issues over on the Nautilus side but for the opposite reason, ie how to explain pearl aragonite microstructure not found as yet in the shell?or in any suitable mollusk shell for that matter.

 

[Lagoon Island Pearls]

As for the epithelial question, it is the core of the 'gonad dilemma', given abalone horn/tooth pearls' nacreous composition matching that of the inner layer of the shell.

Dealing with some similar issues over on the Nautilus side but for the opposite reason, ie how to explain pearl aragonite microstructure not found as yet in the shell?or in any suitable mollusk shell for that matter.

From photos, the horns are certainly a matrix of organic and crystalline structures similar to the shell, many of them seem to have open ends, exposing higher concentrations of conchiolin. This is similar to a post I made some time ago in the nautilus thread about protein compositions in cephalopod beaks (where no calcium is present, likely due to acidity from gastric juices).

In mollusks, differently located mantle sections from the same donor animal can cause marked differences in pearl surface quality when grafted into another animal. If this were the case in abalone, then wouldn't we see a ratio of concretions to nacreous? In the absence of concretions, blood ph might be implicated.

With humans, infection of the GI tract or genitals can cause serious autoimmunity issues (ie) arthritis, attachment inflammation, skin lesions and iritis (to name a few). Strept can give rise to rheumatism, tetnaeus to lockjaw (reactive arthritis) etc.

 

[SteveM]

One thing I have noticed, when abalone pearl sources are asked to explain the commonly-believed gonad origin of teeth/horns, no answers are forthcoming other than 'that's where the diver found it.' Given the high prices paid for these pearls, maybe it's time to learn a little more.

 

[SteveM]

From the latest (2010) CIBJO Pearl Book definitions, the official position of the industry on this genre:

5.79. Gonad pearl
a horn or cusp-shaped natural pearl common in abalone (5.1), formed in the similarly shaped reproductive organ or gonad (5.78).

I guess everyone's been speaking to the same divers.

 

[Tango]

Hi all,
trying to answer to the initial question, the haliotis gonad is horn shaped as has already been mentioned, but inside it there is another organ called hepatopancreas, something like our pancreas and liver togehter. When the pearl grows it fills the cavity and this is the origin of the shaped and hollowness.

 

[SteveM]

Hi all,
trying to answer to the initial question, the haliotis gonad is horn shaped as has already been mentioned, but inside it there is another organ called hepatopancreas, something like our pancreas and liver togehter. When the pearl grows it fills the cavity and this is the origin of the shaped and hollowness.

Thanks, from a most credible source (and no doubt occasional diver?)!

To rephrase, the gastropod digestive organ is surrounded by the larger reproductive organ, the digestive organ forming the core of the pearl, later to decay/disintegrate.

Is Haliotidae unique in this anatomical arrangement?

Yet the essential question remains unanswered: How does mantle/epithelial tissue become introduced into this region for the production of nacre?

 

[Lagoon Island Pearls]

Yet the essential question remains unanswered: How does mantle/epithelial tissue become introduced into this region for the production of nacre?

For foreign epithelial cells to penetrate, survive and regenerate within multiple layers of tissue (whether environmental and/or physiologically) does not seem plausible to me.

Perhaps a tangent, but Tango's post supports the theory, gonadal pearls from gastropods are cystic in nature.

Though not gastropods, some annelids (namely oligochaetes) posess calciferous glands, which coincidentally are adjacent to the reproductive organs. While anatomically dissimilar from abalone, it's possible a process along these lines is implicated in horn pearl formation.

This is from Barnes (1963) "The calciferous glands are excretory rather than digestive organs; they function in ridding the body of excess calcium taken up from food and in maintaining constant pH in the blood and coelemic fluid by controlling the levels of calcium and carbonate ions. When the level of C02 in the blood becomes excessive (with a consequent lowering of the pH), the carbonate ion becomes bound to calcium in the calciferous gland and is excreted into the esophagus as calcite, which is not absorbed in transit through the intestine."

Barnes also describes the hepatopancreas as this: "The site of enzyme production, absortion and food storage. The digestive secretions, which are initially passed to the stomach, contain the usual array of enzymes and in some species, cellulase and chitinase as well."

So Steve, although I'm comparing apples to oranges and despite my lay knowledge of haloitis, can you see where I'm going with this theory?

 

[SteveM]

…can you see where I'm going with this theory?

What I can see is that we are stepping into unexplored territory here. 'Calciferous glands' does not translate to mother-of-pearl, a highly specialized aragonite crystallization associated exclusively with the shell.

As mentioned in my earlier post, this discussion is linked to current work with Nautilus, whose renal appendages have been theorized for decades to be 'reservoirs' of calcium for use in periodic septum formation. Only in the past few months has this been scientifically confirmed, to the great excitement of teuthologists (those who study cephalopods). But aragonite crystallization from the calcium base is a mantle function.

So again, the key question is, how does nacre arise within the gonad of the abalone?

 

[Lagoon Island Pearls]

What I can see is that we are stepping into unexplored territory here. 'Calciferous glands' does not translate to mother-of-pearl, a highly specialized aragonite crystallization associated exclusively with the shell.

Of course it doesn't translate, other than my point being there are soft tissue glands (other than mantles) which perform regulatory functions of fluids which contain the same components as extrapallial fluid. If for some reason, these glands become blocked, infected or no longer hormonally triggered, there are likely to become cystic.

But aragonite crystallization from the calcium base is a mantle function.

Exclusively? I'm not so certain. Can you link me to a description?

So again, the key question is, how does nacre arise within the gonad of the abalone?

%

 

[SteveM]

Can you link me to a description?

Nacre is formed in the extrapallial space (between mantle and shell, or between pearl sac and pearl), that gives rise to the formation of the interlamellar membranes that are the precursors (the molds, so to speak) for the creation of nacreous aragonite tablets.

Are you proposing that the existence of abalone gonad pearls demonstrates that the gonad/hepatopancreas interface (assuming hepatopancreas has become calcareous/cystic) operates as a defacto extrapallial space?

 

[Lagoon Island Pearls]

Are you proposing that the existence of abalone gonad pearls demonstrates that the gonad/hepatopancreas interface (assuming hepatopancreas has become calcareous/cystic) operates as a defacto extrapallial space?

Yes. Mainly because being so highly nacreous in nature, all of the necessary components are present in the blood, pallial fluid and digestive juices. Protein, calcium and most importantly... bicarbonate. HCO3 is vital in the pH regulatory system. It's very important because digestion requires high acidity, whereas other tissues within the same anatomy (especially nerves or even an empty stomach, for that matter) could become damaged. There is a fine line outside the acceptable range of pH, where proteins are denatured and digested or enzymes lose their ability to function.

To me, this seems more plausible than the introduction of foreign epithelial cells.

 

[SteveM]

This is great. Despite repeated searches of the scientific literature I have yet to find anything even remotely as specific as the conjecture here regarding haliotis gonad pearls (the germ of science being, after all, conjecture).

Perhaps Pearl-Guide will get credit for another one?

 

[barbie biggs]

That is very interesting. I was name-dropping monoplacophorans the other day, but you've got me beat with mucopolysac! Cool.

Hah! As a prior respiratory therapist I have to confess that things that started with 'muco' anything were pretty much up my alley for about 20 years.
How that would affect a pearl I cannot say but I've seen some cool looking branches of fungi pulled out of people's lungs. They are called 'casts' and look exactly like the section of lung they come out of. They fill up the alveoli and harden in the shape of the bronchiolar tree and maintain that shape when they are removed. Unless they break of course.
Not terribly pearlish. But pretty much parasitic, just like pearls. Nice shade of green too. Awfully hard to breath around though.

barbie

 

[GemGeek]

Ouch! Sounds like something a mycologist would love.