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Southwest Florida Shells with Emphasis on Sanibel & Captiva

By José H. Leal

Family Pholadidae

Martesia striata

(Linnaeus, 1758)

Striate Piddock

Shell size to 65 mm; shell shape variable, usually pear-shaped, thin. Sculpture of fine concentric, denticulate ridges anterior to oblique groove; ridges smooth posterior to groove. Very destructive wood borer. Anterior accessory plate (mesoplax) nearly as wide as narrow, circular or squarish with rounded edges, with sculpture of fine wrinkles. Juveniles circular in outline. The Striate Piddock uses the anterior end of its rough shell to bore through wood. Piddocks use a semi-circular motion to "drill", creating a long, cylindrical hole that is occupied for life by the animal. When crowded in a piece of driftwood, piddocks may become reproductively active at small size. To collect their shells, look for “Swiss cheese-like” driftwood with the characteristic boreholes indicative of their presence. Supplementary images show piddocks in their driftwood habitat, and the last image is a detail of the apophyses, attachment structures for the paired foot muscles, which are responsible for the rocking drilling motions.