Alternate Title

Morphometrics of the Burrowing Clam Diplothyra smithii Tryon

Document Type



Diplothyra smithii Tryon, a small bivalve mollusk, is a common inhabitant of the calcareous shell material of the American oyster, Crassostrea virginica Gmelin. Large populations of this clam are found on commercial oyster reefs in the western portion of Mississippi Sound. Several aspects of the population of D. smithii in Mississippi Sound were examined.

On the Pass Marianne Reef, 71% of the live oysters and 44% of the dead shells were infested with D. smithii. The mean number of clams removed from valves of live oysters was 22.1 ± 1.7 (range, 1-109; N = 146). Infested dead shells had a mean number of 23.7 ± 2.6 (range, 1-103; N = 75) clams per shell. Clams from live and dead shells indicated monthly variations in morphological stages. During January through April, clams were predominantly immature. In late spring and early summer, clams matured morphologically. In May and June, the majority of clams were mature. Immature clams from early and midsummer spawnings appeared in July and August. Mean lengths and heights of clams with and without a callum and the monthly changes in those dimensions were determined for clams from live and dead shells. All clams from live oysters had greater mean dimensions and size ranges than clams from dead shells. Female clams were significantly larger than nonfemale clams from live oyster shells; females from dead shells were significantly larger than nonfemale clams in length only.

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