I have examined and analysed the few dennal plaques (bones dIat develop in dIe skin) of sturgeon (presurnably black sturgeon (Acipenser oxyrl1ynchus) that you has left widI me several weeks ago. I have al50 examined the documents running down dIe analyses executed at the Department of geology at dIe University of Laval on the SaIne bones of sturgeon and also on the sample of walrus tusk.
On the basis of these observations and in the light of what I know of comparative anatomy of vertebrates and of mammals, which I teach at the University of Laval for more than 25 years, here is what i dIink of your intentionto designate these sturgeon bones by the name of -Sea Ivory-.
According to the dictionary dIe word ivory designates the principal part of a màmmals tooth, which is calied also dentine. In the case of most mammals, the teeth are most I y smali, they have a complex fonn and are covered with a layer of enamel (minerai tissue harder than the dentine). The volume of dentine in most mammals teeth is consequently smali, therefore we don't nonnaliy cali the dentine ofthese ordinary teeth the ivory. We usually reserve the word -ivory- to designate voluminous teeth and in the simple fonn ofwalrus tusks, the homs ofnarvals, ofhippopatamus, and the teeth of the spenn whale. But above ali to designate the elephanfs tusks (Asian and African) that the word ivory was invented. These tusks are indeed very large and are consisting uniquely of dentine. Moreover the Greeks utilized dIe word -elephasto desigante at the SaIne time the elephant and his ivory .
In 50 far as animal tissue, the ivory is essentialiy bone, a tissue that we find only among the vetebrates, being fish, saIne primative as the sturgeon, or mammals such as the walrus and elephant. The analysis results ofthe chemical composition and crystailine structure of the dennal plaques of the sturgeon are dlerefore not suprising : These bones are very similar to walrus tusks. Even more the sturgeon bone presenting on the inferior surface (that which is turned toward the body of the fish) has a dense and lusterous aspect which resembles the ivory of a walrus or elephant.
Therefore it seems to me that you are justified to calI these sturgeon bones ivory, aU the more as the characteristic fonn of these dennal plaques prevent any possible confusion with the ivory of an elephant, which commerce menaces the survival ofpresent day elephants. We use the expression -vegetable ivory(or corazo) to designate the hard seeds of the South American palm tree (with this we make buttons). With regard to these seeds, sturgeon bone has everthing in common with vegetable ivory .
Finaliy when considering ifs method ofreproduction, the black sturgeon is a species sensitive to commercial overexplotation. Actualiy the species is not considered menaced in Québec, but is stili on the officiallist of Québec verebrate species susceptible to eventualiy become designated as menaced or vunerable. 1 believe that the commercialization ofthese dermal plaques, a part of the animal normaliy ignored by fisherman, does not risk at the short-term to add to the menaces that weigh upon the Québec population of this species. In this respect. the utilization of the word -ivory- , which evokes dIe unfortunate rate the ivory commerce has caused elephants, can have a positive impact, in attracting the attention, not only of the and rarity ofthese bones, but on the necessity oftreating the producing species with priority number one being ifs long-term survival.