A well-known song‘s opening lyric declares, “It's been a long time since I Rock-and-Rolled,...” It has been a much longer time, however, since the first compound microscope was invented in 1595 (CE), and longer still that humans have been interested in the shells of cowries. I was surprised, then, that two external features on shells of Cypraea teres Gmelin, 1791 seem to have gone undetected up to the present. I happened upon these features while using a low power, binocular microscope to examine many different Hawaiian specimens of this cowry.

Figure 1 One fluorescent tube was masked off to produce a thin line of light; it was used for all of the images shown here. Variations in the shiny surface of the cowry's shell can be interpreted by its highlights. On this shell, from right to left, there is one ridge between the first two large spots and two between the second and third. See the caption for Fig. 2.

The first of the two features is marginal pitting—attenuated, but regularly found—at the juncture of the labial callus and the dorsum on C. teres. It is most easily seen by using a microscope; shiny, unworn shells which have only a few dark spots on the dorsal edge of the labial callus (see Figure 1) are the best subjects. Some care has to be given to choosing a light source. One bare fluorescent bulb several feet away serves better than a broad lamp up close (see Fig. 1 caption). The pitting is created by slight ridges which extend onto the dorsal area from the labial callus. I have also noted this ‘new’ feature on every other ‘form’ of Hawaiian C. teres; some of them have taxa proposed, others do not. Observing the pitting is not easy due to the subdued expression of the ridges, and made more difficult to see because of its white-on-white composition. A common but separate trait on C. teres can obscure some or all of this pitting; that feature is dark spots on, or close to, the upper surface of the labial callus. A shell with many of these spots, which are raised by tubercle-producing papillae, may not show marginal pitting because a large spot can ‘sprawl’ far enough to cover the pit structure both under and on either side of it.

Upon finding this pitting on shell after shell in a large sample of Hawaiian C. teres, the thought occurred that such a feature might also be on shells from other locales. By checking a half-dozen specimens of C. teres from the Philippine Islands, it was soon clear that this was on shells from at least one other area in the Pacific Ocean. Then I contacted another worker in the Cypraea, Eduard Heiman of Israel. He e-mailed back that, under magnification, the C. teres from waters off the Sinai Peninsula also show this ‘new’ pitting. Additionally, Mr. Heiman was able to confirm, in his local population of C. teres, a second feature which I had found on Hawaii's C. teres, ‘shimmering’ lines, or striae (see Figure 9), on the marginal callus; markings similar to these can be found on other varieties of cowry in the Indo-Pacific region.

Figure 2 A full labial view, from a slightly different angle, of the shell in Fig. 1. More ridges are visible between the last two large spots. See Appendix for parameters of all shells shown in this item.

The explanation of just how this marginal pitting is related to an article about the strange forms of Cypraea teres found around Oahu, Hawaii, begins after I give the reason Oahu itself was singled out. It is the Hawaiian Island which has had more skin- and SCUBA-diving shell collectors than the others. I must include, as well, many tide-pooling, beachcombing landlubbers and several intrepid crews of off-shore dredgers. This island is where more odd forms of C. teres have been found because more collectors are—or have been—working here.

Now that explanation,... Marginal pitting on C. teres suggests that it may have a much closer conchological (and genetic) alliance to the cypraeid sub-genus Erosaria Tröschel, 1863 than previously suspected. It may also give cause for reconsidering the relationship between the subgenera Blasicrura Iredale, 1930 and Erosaria. One variety of Hawaii‘s C. teres has had its own taxon for more than a century—C. rashleighana Melvill, 1888 (see Figures 4 & 6). It certainly doesn't seem to be a C. teres, but how does it truly differ? Difficulties associated with this group of cowries most often stem from viewing each as an essentially complete and indivisible entity. It is more helpful to consider any cowry as a living assemblage of mostly function-enhancing features attached to a visceral ‘package’ that itself can successfully “feed and breed.” So long as those two absolutely essential functions work, almost any feature could be associated with them if it did not detract from either. A few straightforward examples of such ‘associations’ are given below.

Although traits such as these are inconsequential to the ‘feeding and breeding’ of the cowries themselves, they can be employed as genetic ‘markers’ when studying the relationships among some varieties of these animals. Cowries which possess conchological features like these also share the common genetic material which causes such traits to be expressed. This premise will be used below to form a query about C. rashleighana and its parentage. It may be challenging for readers to visualize the upcoming abstracted descriptions of cypraeid phenotypes (physical forms) and genotypes (genetic arrangements), and if I err now, it is on the side of clearer understanding in humbly offering a brief scenario using known human genetic traits. This writer apologizes in advance should the following allocations—meant solely to illuminate cypraeid genetics—raise the ire of a sensitive reader.

Figures 4 & 5 Labial views of a C. rashleighana (above) and a C. cernica. (All shells taken at Makua.)

Returning to the query mentioned earlier, I chose a cowry ‘parent’ capable of contributing traits to C. teres which will transform it into C. rashleighana. This parent adds a columellar callus where teres has no development at all; this parent adds marginal spotting far more plentiful than teres has; this parent has an inflated shell where teres is elongate and almost cylindrical; this parent has widely dispersed spots where teres has spots which mostly line up on its marginal callus; this parent has relatively small, brown spots where teres has, for its size, relatively large spots which can shade toward black; this parent has weak fossular development toward the posterior of the columellar aperture where teres has strong development all along its columella; this parent has a dorsal pattern which spreads color widely over the area while teres tends toward broken banding and blotches. These seven traits alone go a long way toward altering the form of C. teres and causing it to appear very much like C. rashleighana, but I have only named a few Mendelian-like features. There are also multi-locus characteristics which complicate the ‘picture’ to a far greater degree.

Figures 6 & 7 Columellar views of the same C. rashleighana (above) and C. cernica.

The parent which has the features needed to transform C. teres into rashleighana is Cypraea cernica Linnaeus, 1758 (see Figs. 5 & 7 [and see this shell, plus four more, in the Visual Database of Cypraea teres-related Shells]). To build on the example of dominant/recessive gene expression given above, consider a scenario which gives a partial explanation of how C. teres and C. cernica give rise to rashleighana by the mixing of their genes. The ‘dominant’ parent is C. teres and the ‘recessive’ parent is C. cernica. Their mating—and the subsequent localized “bloom” of their offspring in the relatively quiet waters of any one of Oahu's many drowned sinkholes (often called “pockets”)—sets the stage for an explosion of the diverse forms of C. teres.

When these heterozygous f1 offspring (f1 signifying the first filial generation) created by this dominant teres and recessive cernica union begin to mate amongst themselves, every single block on the following Punnett Square represents a possible outcome for their spawn, the f2 generation. The unaltered teres phenotype of the f1 population belies the explosive genetic potential in their genes.

An additional mating possibility is that one or more of the f1 group will ‘backbreed’ with one of its parents, either the dominant teres or the recessive cernica. While the chance is small, it is possible that an offspring of this f1 population will find, or be found by, one of its parents (if they have not fallen victim to predators). Should that mating occur, the eruption of forms would be limited to the half of the Square ‘ruled’ by that parent, i.e., a triangle with that parent at its apex and the diagonal line from upper right to lower left corners as its base (see explanation after Table 2). If that ‘parent’ were the cernica, many of their offspring would probably produce cowries that look like C. rashleighana. On the other hand, if the teres were involved in the backbreeding, the greater part of those offspring would appear to be mostly teres-like and the genetic material needed for rashleighana to reappear would be virtually overwhelmed by the vast gene pool of the teres tribe. This does not totally eliminate the appearance of an occasional C. rashleighana, but it leaves a sheller hoping for the equivalent of a jackpot on a six-wheel slot machine—long odds, indeed!

Should the following array of genotypes seem imposing, it is. The complexity of this Square plus the lack of hundreds upon hundreds of specimens for study are two probable reasons that ‘experts’ have steered clear of explaining the many forms which Hawaii's Cypraea teres takes on. Only seven overt conchological features were mentioned above—there may more than a dozen discernible between teres and cernica—yet the array below represents only four. Most readers will be familiar with the first few powers of 2; a Punnett Square for the seven traits above would require a 128×128 array in place of the much ‘smaller’ 16×16 square below. That larger plot would reveal 126 stable “races” in addition to those of the two parents!

This Punnett Square has two main features which need emphasis. One is a diagonal line of stable genotypes running from the upper left to lower right corners; at its ends are the ‘parents.’ Between them are fourteen other homozygous ‘races’ of this cowry. Each would breed ‘true’—for the four traits represented—in its own group, producing offspring with the same genotype and the same phenotype (physical appearance). Those offspring, in turn, would produce more of that same “race,” breeding amongst themselves. Any one of these races would produce shells which were “consistently different” from any of the other homozygous varieties along that line, including the parents. That phrase—“consistently different”—is invoked time and again by proposers of new specific taxa for cowries.

The second noteworthy feature in Table 2 is at its lower left corner. This position represents the generation produced by this hypothetical union of a dominant parent and a recessive parent. It shows the single genotype which results from the ‘mixing’ of the two modes of those parents’ traits. This genotype, as mentioned above, is known as the f1 (first filial) generation. When this genotype interbreeds with its siblings, all combinations in Table 2—even its own—represent possible offspring. I make the assumption here that each trait in Table 2 is on a separate chromosome and, due to random spindle attachments in Anaphase I (and, again, in Anaphase II) of meiosis, the alignments of homologs and chromosomes carrying each trait will also be random, i.e., it is the same as rolling dice. (The ‘science-speak’ is provided to make clear a technical point of genetics.)

The presence or absence in collectors’ bags of Cypraea rashleighana is often labeled as ‘cyclic’ or ‘periodic,’ yet no one seems to be able to lend a reliable time interval to those terms. As this article’s title suggests, C. rashleighana and the other rare teres-like shells do not march to any drummer of which we are, as yet, aware. It was mentioned in the Hawaiian Shell News of October, 1988 that the much-desired rashleighana will not be found in any notable quantity around Oahu until C. cernica is again being taken at SCUBA depths. My fresh musings (above) about the role of cernica in generating a swarm of rashleighana suggest serendipity plays a large part in whether more rashleighana appear or not. Additionally, severe weather like Hurricane Iwa in the early 1980s or the recent heavy storms which dumped tremendous rains (Feb., 2004) on the Hawaiian Islands wreak havoc below the waves by smothering life forms indiscriminately with silt washed from the land. A ‘delicate’ series of mating events, like that mentioned above, will probably be stopped dead in its tracks. (Oddly enough, a concurrent, extended period of high surf on the northern and western shores of Oahu offered some hope that much of this slit may not have had a chance to settle in the underwater pockets and bays before it spread out to deeper regions. This is one of those rare instances when the surfers and the shell enthusiasts are in league as both “Pray for Surf!”)

The thoughts above hint that C. rashleighana should remain a proposed taxon because the animal which produces those highly variable shells is very likely nothing more than a ‘form’ born of two other kinds of cowry, themselves thought to be distinct “species.” How can two separate species interbreed successfully?... By not truly being separate species! That, of course, means,... if C. cernica and C. teres are not distinct species,... what species are they? Well, I don't pretend to know, and this item is not about making new names, it is about exploring how meaningless the ‘old’ taxa are when applied to the wide variety of forms which comprise this population. I am primarily concerned with facts, if I can get them,... or reasonable guesses based on what facts are available. Lacking accredited schooling in “academic science,” I limit my work to “frontier science.”

The existing ‘names’ of all the teres-like animals are, to my mind, proposed taxa. What this ‘new’ finding seems to reveal is that those propositions are—at best—based on ‘hunches.’ When nearly 1,000 of these shells are studied closely, there is strong conchological evidence suggesting that its many varieties are only forms of some more-inclusive genetic entity. The ‘proposers of taxa’ need to show that their ‘species’ are either temporally isolated in their mating patterns or that they are behaviorally estranged,... because these groups are, after all, sympatric and it must be shown that something is actually preventing the intermingling of their genes if they are to be considered truly separate species.

Figures 8 & 9 C. teres with faint striae across its anterior labial tubercles. These are best seen from this angle on this particular shell.

The newly discovered marginal pitting on C. teres is an important find now because, as mentioned above, it links teres even more closely to cernica. Marginal pitting is a major common feature of the Erosaria, yet who would now seriously champion a suggestion that C. teres should be moved to that sub-genus from the Blasicrura? It would more valuable to workers in the Cypraea if the systematics of the cypraeid subgenera were re-evaluated. This last suggestion arises from the co-discovery of that second conchological feature on shells of the “teres complex” (although this last phrase means less now than ever before). This other feature on C. teres, seen under moderate magnification (~10×), is ‘shimmering’ striae on the labial callus. These are more easily seen on the darkly pigmented tubercles found on the dorsal side of the callus, mostly on anterior spots, but occasionally on some toward the posterior. These markings are very similar to those found on the margins of cowries in the sub-genus Lyncina, Tröschel, 1863, e.g., C. vitellus, C. schilderorum and C. sulcidentata. A notable difference is that the marginal striae on C. teres are longitudinal (axial), unlike the latitudinal (radial) marginal markings of the Lyncina. These ‘new’ striae are mostly visible on unworn specimens of teres, and only when viewed from a specific direction (see Fig. 8). The best viewing angle varies somewhat from one specimen to the next. This feature again brings up question of just how well the current scheme of sub-genera describes the actual condition of the Cypraea.

Prior to summing up the assertions and ideas put forth above, I would like to point out that the International Commission on Zoological Nomenclature (ICZN)—paraphrasing the information found on its official website—basically rules on the validity of a proposed taxon, not on the validity of that proposal. That is to say, the ICZN does not ask, ‘Should a new taxon be proposed?,’ it only asks, ‘Has the proper method of proposing a taxon been followed?’ One does not study the cowries for long before this tacit fact becomes obvious. With animals like the Cypraea, whose life cycle is intimately entangled with free-flowing ocean waters, a high degree of certitude is difficult to achieve when making pronouncements about living animals’ specific status. The level of certainty acceptable to proposers of new cypraeid taxa too often seems subject to non-scientific pressures. The result, almost without exception, serves some purpose other than that of advancing our understanding of cowries.

The ‘new’ features mentioned here present only one of several known instances where the generally accepted idea of what a cypraeid species is thought to be falls short of reality. There also are the cases of the C. schilderorum × C. sulcidentata ‘half-breeds’ (to see an article about intergrading shells, click here) and the C. granulata × C. nucleus ‘throwbacks.’ The former has been known to Hawaiian shellers for decades, yet not one cowry ‘expert’ felt that the numerous specimens intergrading between two supposed ‘species’ merited comment. In the ‘throwback’ instance, an animal with a shell intermediate to the Hawaiian C. granulata and the Indo-Pacific C. nucleus was taken alive, with a granulata ‘mate.’ (The shell is pictured in the Hawaiian Shell News of September, 1990 {New Series No. 369, Vol. XXXVIII No. 9} and on-line at www.cowrys.org/archive/.) Again, the silence following that find was deafening. There are other articles scattered throughout decades of HSN articles suggesting that our understanding of cypraeid species is quite inadequate.

More shells will be studied, and more shells need to be collected specifically for study. There is conchological cowry work here for years to come, and a few other workers are also at tough tasks. Additionally, I am working on population statistics for several endemic Hawaiian cowries,... and other things, as well. Some results of that research into Hawaii's cowries can be found in other items in this site. In time, the databases themselves will be on-line and available for others to use for research. This new century, with its new tools, promises great additions to the work already done in centuries past. I certainly intend to do as much as possible to see that promise unfold; however, if any others with interest in the cowries wish to help, even more candles in the dark can only help.