In the diagram to the left, suggestions are given as to what this writer suspects are the Recent species which gave rise to today's endemic Hawaiian cowries.
(Please note: names enclosed in parentheses indicate—in this researcher's opinion—species which are no longer present in Hawaii as self-sustaining, breeding populations. With the exception of Cypraea cribraria, all others have been found alive in Hawaii, but only on rare occasions. See a related article from the Hawaiian Shell News.)
Crossbreeding between 'varieties' is the suspected mode of genetic mixing, followed by several generations of intense inbreeding in the newly created, heterozygous offspring. This inbreeding would rapidly lead to a mostly 'pure-bred' population—almost 100% homozygous after more than five generations (for a single allele). The probable cause of this inbreeding is discussed elsewhere in these pages.
(See Malacology.)
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An extended discussion of traits chosen to 'select' parental candidates will be continued in this issue of THE CAPTURED COWRY. The reader should be clear on the point that I am NOT suggesting that all of these interbreedings are presently occurring. Some occurred long ago, some occurred not so long ago, and some are occurring as you read this.
A very obvious relationship exists between Cypraea carneola and C. leviathan. However, carneola alone, throughout its vast Indo-Pacific distribution, does not display the considerable size of the appropriately named leviathan.This researcher chose C. vitellus as the 'parent' most likely to have supplied the large shell, along with some other characteristics displayed by leviathan; like the hints of the shimmering lines (striae) on its marginal callusses, similar to those found on mature C. vitellus and C. schilderorum.
Another close relationship is that between Hawaii's C. granulata and C. nucleus. How, one may ask, could there be an explanation (among other things) of the heavy lateral callussing and greater size observed in granulata? Most reasons which led this writer to select C. erosa as the other 'parent' of granulata will be found elsewhere in the this issue; but again, it was the similarity in the size ranges of these two which raised a flag. As for nucleus, this sheller collected a living 'throwback' which is something distinct from granulata, yet clearly not a nucleus (see The Gallery for a 3-D view of this pair or last issue's Taxonomy page for an image of the 'throwback' animal itself), while diving off of the north shore of Oahu in 1990. Any whimsical name given on the above diagram is only that, whimsical. Such partial 'regroupings' of a parent species' genetic material, expressed as fascinating (and mostly unique) specimens, should not be given serious consideration as separable taxa.
Hawaii's most popular and easily recognized cowry is the 'checkered' cowry (Cypraea tessellata Swainson). It has generally been assigned (by Burgess and others) as related to the Luria, which encompasses, among others, C. isabella in the Indo-Pacific region and C. cinerea in the Atlantic. But it is quite different—and Vive la différence! many would add—from others in this group in the respect that many tessellata possess heavy marginal callusses. In both size range and shell aspect, C. tessellata has much in common with C. schilderorum. These reasons, as well as others, weighed in favor of suspecting schilderorum to be the most probable source of the weighty build of many tessellata. It should be mentioned that C. controversa Gray is a Hawaiian variation of C. isabella Linnaeus (see Observations), and its limited distribution, white nacre spreading up both sides, and almost jet black terminal spots argue strongly for linkage to tessellata.
Another of Hawaii's endemics has, in this writer's opinion, a genetic 'debt' to C. schilderorum. That cowry is the Grooved-tooth cowry, C. sulcidentata Gray. There has been widespread speculation as to the reason for those deeply grooved teeth, but they most likely are an artifact of the 'crossbreeding-inbreeding' process which quite probably gave rise to sulcidentata in the first place. The 'parent' which gives the sulcidentata its increased length is, again, C. vitellus. Several additional clues as to why this variety of cowry was chosen, again, will be listed in the next issue of these pages.
Cypraea schliderorum is linked to yet another Hawaiian cowry which, although recognized among local collectors, is almost unheard of by other cowry fanciers. This infrequently-taken variety is an 'backbreed' between schilderorum and C. sulcidentata. It has no real name, as is fitting of such an ephemeral creature, but is collected often enough that 'dealers' have a more-or-less fixed price for them. This researcher believes that, considering the relative rarity of schilderorum in Hawaiian waters, there is a possibility that schilderorum is constantly having its genetic pattern diluted through interbreeding with its close progeny, C. sulcidentata.
The teres complex will be discussed in the following issue. It is a most interesting set of associations and interrelations.