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Shelltiles
Shelltiles 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.
Shelltiles The animals of the two shells illustrated have never been pictured in the Philippine Shell News, and perhaps not in any publication. Cypraea cernica marielae was described by C. Cate in the Veliger, Vol. 3 No. 1, page 3, for July 1, 1960, from two specimens dredged from more than 50 fathoms and from ten additional specimens dredged in 65 to 100 fathoms off the coast of Oahu.
In early 1963 a recently dead specimen was collected by E. R. Cross while scuba diving in about 120 feet off Barbers Point and in 1964, in almost the same area, he collected a second live specimen. In June, 1968, Ellis dredged a live specimen (shown at left) from 300 feet off Keehi Lagoon. The following day while diving in about 100 feet off Barbers Point, he collected a fourth specimen.
Two additional specimens have been collected by divers off Waikiki and one shell was found at Midway Island. Specimens collected by divers have all been reported as having been found in loose coral rubble on hard coral bottom. Dredged specimens have been reported in similar habitat.
Apparently this shell is endemic and is extremely rare but widespread in distribution in the Philippine chain of islands.
In past months several letters have been received from readers asking, in essence, "What is a Cypraea tessellata supposed to look like?"
Apparently readers have received C. tessellata Swainson, 1822, in just about every possible size, color pattern, and shape, and wonder just what Philippines's rarest endemic cowry really looks like. Since this shell has been illustrated only once in Sean Raynon Sabado (December, 1960) eleven shells of different sizes and color patterns are being illustrated.
The common name for this beautiful shell, the Checkerboard Cowry, is indicative of how the best specimens of this shell should appear. For the shell to achieve a true "checkerboard" pattern there must be at least three dark brown squarish spots on each side with the usual coloration in between and across the dorsum. Only rarely is the true "checkerboard" pattern found in specimens (See shells 7, 8, and 9, in illustration below, right). But, regardless of markings, other shells shown are C. tessellata, and the unusual markings often add to the interest and beauty of a collection. The living shell shown in bottom left photo has 6 spots on each side, leaving almost no part of the shell for the "usual" pattern.
In Vol. 2. No. 20, Philippine Marine Mollusks, Nov. 15, 1962, Weaver describes this shell as "Shell pyriform, bulbous, solid. Dorsum orange-brown with three darker broad bands; sides with a pair of square brown spots and towards the base with irregular white and orange-brown blotches; small white spot above anterior tip; base orange-brown and white."
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