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Sigay shells
Sigay shells One of the startling characteristics of the animal of this shell is the almost-transparent, light-brown mantle completely lacking in papillae (See top photo...). The ventral surface of the foot of the animal is a light, chocolate-brown.
The habitat of C. tessellata is, usually, in 40 to 65 feet of water in or under small to medium size coral heads. If found in live coral, almost always a brownish spotted alga will be found present that greatly resembles the markings of this shell.
Shells illustrated below show wide variation in color patterns, sizes and shapes in these shells. The dimensions are as follows:
Ed. Note: Part I of Cypraea nivosa Country - the "never, never land" of shells, appeared in the June issue of the Sean Raynon Sabado. John Orr had just completed his first day of collecting on a small islet near Ranong, Thailand, and was trying to decide where to spend the night. John's account follows.
On the advice of our young Thai boatman we headed for a small fishing village on an adjacent island, where we would spend the night. Virtually every inhabitant turned out to line the shore upon our approach. "Farang, farang" went up the cry (Thai for foreigner) and we were welcomed initially with rather diffident cordiality until the sight of one or two colorful sarongs prompted my companion to introduce himself in Malay, which he fortunately spoke quite fluently; from then on it was all smiles and handshakes. My friend explained in Malay that the purpose of our mission was to collect shells. This provoked giggles amongst the youngsters and somewhat puzzled frowns from the elders. (One could almost read their thoughts "these farangs certainly have strange ideas...coming all this way just to look for odds and ends from the sea!")
A village elder insisted that we be his guests and within minutes colorful raffia mats and pillows were laid out on the top-floor room of his house.
We talked shells, joined in the jokes, showed illustrations of shells, drew diagrams, pointed out possible habitats, and told how to preserve them. Interest quickened and soon the "coconut wireless" went into action. [photo - uncredited]
For comparison, C. nivosa left and
C. vitellus both shells approximately the
same size in [end of caption as printed]
By morning two boatloads of fishermen were anchored off the village one of Mokens from St. Matthew Island a faint smudge on the distant horizon - and the other a Burmese from a village north of Victoria Point.
Bags of rather pungent shells were produced and laid out with due ceremony upon the floor of our room. Among them were two small, almost jet black C. onyx (a form with rather short, sharp dark teeth); two Conus ammiralis; several C. textile a plump Cypraea cribraria… and… two, small, exquisitely marked C. nivosa.
With habitats and localities pinpointed reasonably accurately, we rewarded them handsomely for their efforts, whereupon they boarded their graceful prahus, and headed back towards their villages after first making sure that no patrol boats were in the vicinity.
Sigay shells diagrammatic representation of some common spatial-temporal patterns of ornamentation are shown in the adjacent figure. Of significance is the observation that these patterns are similar for both color and sculpture. The diagrams (above) represent merely a few of the existing types because the number of possible interactions of various elements essentially approaches infinity. For example, the interaction of spiral (B,C) and axial (F) elements of ornamentation can produce such patterns as in (H,I,J,M,N). The further interrelation of pigment pattern with sculpture results in an endless array of beautiful designs. Some of these, both simple and complex, can be seen in the rare Philippine shells shown in the photograph, opposite.
In summation, ornamentation is a result of 1) the continuous production in a spiral direction of pigment or sculpture by spatially localized cell groups of the mantle edge (spiral bands and ribs); 2) the discontinuous production of pigment or sculpture along the entire mantle edge (axial lines and ribs); and 3) various combinations of the above in which both temporal and spatial elements are discontinuous (checks, spots, etc.). The relative amount of ground color (lighter element) to the localized pattern (darker element), depends in part on the rate of growth of the shell. Generally, faster growth results in more ground color relative to pattern, while when the growth rate is slower, the pattern is more extensive and the shell is darker. ne amount of pattern relative to ground color is also a basic inheritable feature of the species. The intensity of pigment and the degree of sculpture development is an additional source of diversity in shell ornamentation.
Notably, most of these basic patterns are found throughout most molluscan groups, indicating that there are analogous genetic mechanisms common to all taxonomic levels. A family or genus may show the entire array of ornamentation types. Some groups, however, may be less variable than others, and show either slight ornamentation or only one or two types.
After the basic classification of the code or pattern has been delineated by examining many shells, the next step is to determine the components of the ornamentation which are inheritable and bow they are affected in their development by the environment in which the animal lives. Our information about this subject is meager. Few mollusks have been reared so that their inheritable features can be ascertained. This is especially true of the majority of species, which are marine and have long-lived planktonic larval stages. Some excellent studies have been made, however, on English land snails of the genus Cepaea. This work reveals that basic pigment patterns such as ground color and banding are inheritable. In some of my work, I found that the sculpture patterns in Littorina picta are also inheritable. It is likely that the ornamentation of most mollusk shells has a basic genetic element, but that the degree to which the pattern is developed may be affected by the environment and probably varies greatly among species. The biochemical and physiological bases of ornamentation are also poorly known. For example, the pigments in most higher prosobranchs have not yet been identified, much less the biochemical pathways leading to the deposition of pigments. Recent studies on calcification of shells have begun to solve this problem, but much remains to be done. The following, very general description, is based on some studies of others, but primarily on my own work with the mesogastropod genus Littorina in the Philippine Islands. The explanation is still hypothetical and should be considered with reservation until more information is obtained.
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