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Hey Dave! Tell us how you got the pearl please! There has got to be a story for this one
I came late to this intriguing thread but couldn't help myself when the question of pearls in other cephalopods came up. I touched on the harvest
here.
While I was a geoduck diver, a scientific expedition was taking place near Tofino. A group from Simon Fraser University was studying the growth rates in O. dofleni, aka Giant Pacific Octopus. I was often contracted to capture, then return animals to their dens. At the time, we used a dillute solution of water and bleach in a soap bottle to cause the specimens to leave the den for bagging. Interestingly enough, most of these would simply volunteer for recapture, rather than deal with the effects of the bleach. After a few months, we became quite familiar with each den and every animal's respective behavior. We would make every effort to return each correctly. Once, I got it wrong, by stuffing a tagged animal into a cave, only to have a giant wolf eel make chase. The octopus immediately found his own den and evaded the eel. Scared the bejezzus outta me
During the study, we learned some amazing things about growth and age. These animals retain more than 25% of their food resources in body weight and have an uncanny ability to retain information about their surroundings (which is a whole other story). Clearly octopus hunt from strategy, not instinct. Owing to the fact they grow fast, their life cycle is short. Apparently giant Humbolt squids only live 500 days.
Once the study was completed and the harvest restrictions were lifted, I returned to the site, knowing I could find an octopus in one of the dens. I was in the water scarcely a few minutes when I found a suitable candidate. Almost immediately I realized this specimen had been in a fight, but didn't appreciate the degree of his injuries until I got him home. Right four was partially amutated while right three was severed at the level of the mantle. There was a oblique healed scar, approx 10 cm. posterior on the mantle itself.
When I prepared octopus (or crabs for that matter), rather than simply removing legs, I always section them with a portion of the body meat as well. Once sectioned, take each piece skin, wash and cut for cooking. In this case, while I made my initial cut, felt a nodule within the scar tissue, less than two inches from the beak. After a bit of crude surgery with a chef's knife, extracted the pearl. I had collected other pearls from mussels and oysters by this time and was actively working on developing pearl culture techniques, but dismissed the octopearl as non nacreous and of little value. I was more intrigued by the coincidence of the amputations. As you may already know, male octopuses rely on the tip of right three (hectocotylis) to copulate with the female. Losing that appendage caused the animal to become sexually over-mature and in all likelyhood extended it's life span by a few years... enough time for a pearl to form.
It was asked by Ana and others, how does an animal with no shell develop a pearl? My speculation would be, the solution is in the donor not the host. The main food source of O. dofleni are crabs and clams. Namely Red Rock Crabs (Cancer magister) and Butter Clams (Soxodomus gigantea). This pearl has an extracrystalline structure similar to the prismatic layers of Saxodomus, but arranged in a spiral, as opposed to terraced.
A possible scenario would be this. Octopus are voracious foragers, even when stressed. This animal likely captured a clam and took it to the den. Once the shell is broken or otherwise pried open, they use their beak to rip tiny pieces of flesh for ingestion. A tiny piece of living epithelial tissue, perhaps connected to a piece of shell at the level of the periostracum, drifted away slightly only to become lodged deep within the injury, where enough of a vascular flow was present and pearl sac formed. This allowed the cells of the donor to divide, multiply and form a complete pearl sac.
It's a lot of guess work, but it's plausible and seems closer to the mark, than the "throw back" theories of when octopuses evolved out of their shells.
The ultimate coup in my work would be the discovery of pearls in nudibranchs.
Thanks Douglas, for revisiting this amazing thread.
