File:American malacological bulletin (1988) (17968777548).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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120 AMER. MALAC. BULL. 7(2) (1990)
Text Appearing After Image:
Fig. 2. Photographs of six scallops that exemplify the various patterns described in the text. For each shell, the top (left) valve is to the left and the bottom (right) valve, with its distinctive byssal notch, is to the right. Top and bottom valves show different patterns as follows: a) upper- continuous with mottle, lower- continuous with bands; b) upper- continuous with chevrons, lower- continuous with mottles; c) upper- continuous, lower- ribs only; d) upper- bands on ribs only, lower- no pigments; e) upper- continuous with rays, lower- unmarked except in juvenile region which is continuous; f) upper- continuous, lower- no pigments (scale bars = 1 cm). ef a/., 1984) have had white (presumably unpigmented) rays on shells with orange or yellow background. "Mottle & chevron" are white, gray, or sometimes yellow markings that are caused by the active, episodic secretion of a light pigment, not by an absence of color. They occur only scattered across one of the covering patterns. Mottles (Fig. 2a, top valve; Fig. 2b, bottom valve) are rectangular patches of pale pigment usually limited to a section of one rib while chevrons (Fig. 2b, top valve) are "V'-shaped and often extend across several ribs. Whether these two have different causations is not known, and they are grouped in this analysis as "mottle & chevron". There are three covering patterns: "continuous", "ribs only", and "top valve only". In the "continuous" pattern the entire valve can be covered with dark pigment so that only close examination of the auricles will reveal that the background color is white (Fig. 2c and 2f, top valves). In "ribs only" the continuous pigment can occur only on the tops of the ribs and not in the furrows (Fig. 2c, bottom valve). This gives the shell a rayed appearance that is very regular and distinct from the episodically rayed pattern. A banded shell can also show this pattern (Fig. 2d, top valve) because those areas banded with dark pigment can have it on the tops of ribs only or on both rib and furrow. In "top valve only" the continuous pigment, whether marked with an episodic pat- tern or not, is sometimes restricted to the top valve only (Fig. 2f) or to the top valve and the juvenile portion of the bottom valve (Fig. 2e). FREQUENCIES OF SHELL PHENOTYPES All the adult and juvenile scallops collected from Lagoon and Nashaquitsa ponds were scored for appearance of the shell using the classification system described above. The four adult samples from each pond were first tested for homogenity of frequencies and then pooled to estimate phenotypic frequencies for that pond, while the juveniles from all the spat collectors in one pond were treated as a single sample. Three main analyses were then performed. First, comparisons were made between the two age classes within

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