Last year, Hannah Richardson (Naples, Florida) found this unusual shell valve of a Sunray Venus (Macrocallista nimbosa) on Kice Island, Florida (top left). The valve displays an area that lacks pigment, but elsewhere it shows the normal coloration one expects to see in that species. The pale area reminds me of a large “sun ray” radiating from the valve’s beak, or umbo.
The mollusk’s mantle edge creates the shell; specialized cells within the mantle edge produce the pigments that impart colors to the shell. Non-pigmented (“albino” or “albinistic”) shells (bottom right), develop when the lack of pigment production extends to the entire mantle edge.
The partial lack of a color pattern in Hannah’s valve reveals that production of pigments was hindered, but only in a limited area of the clam’s mantle edge. This condition is vaguely analogous to poliosis or Mallen streak, usually a patch or streak of white in an otherwise area of pigmented hair in humans (Cruella de Vil, Lily Muster, and the Bride of Frankenstein come to mind). The fully non-pigmented shell is in the Museum collection (BMSM 66554), collected in Bonita Beach in 1972; it was a part of Janet Paddison’s collection donated to the Museum in 2003.
