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Pectinid Scallops
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Pectinid Scallops

Scallops in the family Pectinidae are a diverse group of marine bivalves and include between 250-400 extant species. Commonly known as scallops, pectinids possess a good fossil record and are found from tropical to polar oceans at intertidal to abyssal depths. Members of the family support economically important fisheries and are cultured successfully worldwide. Most pectinids are easily recognized by their rounded valves and two ear-like projections (auricles) on either side of the umbo. All pectinids possess a ctenolium, a row of denticles along the ventral edge of byssal notch of the right valve that is used for attaching the byssus to a substrate. They possess a series of tentacles as well as numerous simple image-forming eyes along the mantle margin. During early ontogeny, pectinids exhibit a unique compositional change in the right valve, from prismatic calcite to foliated calcite.

Scallop species display an incredibly diverse set of behaviors, including byssal attachment, cementation, and construction of saucer-shaped depressions in soft substrates. Perhaps the most intriguing scallop behavior is an ability to swim. Many of these behaviors define the microhabitat of the adult animal, and can be described as a species’ life habit. In addition, life habit appears to be correlated with particular phenotypic traits.

The extant Pectinidae are classified into four major groups, or subfamilies, based on morphological data (Waller 1991, 2006): the Camptonectinae consists of a single genus, Delectopecten, which may be the sole surviving lineage of a Mesozoic radiation; the Chlamydinae has the greatest biological diversity, with over 30 genera; the Pectininae has 16 genera and includes many of the economically important species; and the Palliolinae contains 12 genera, including several gliding species. Within this taxonomic system, the placement of at least five genera is currently undecided.


Mantle edge of Argopecten irradians with three sets of tentacles and a row of iridescent blue pallial eyes. Photo by William Capman.

contact Dr. Jeanne Serb
Iowa State University
245 Bessey Hall
Ames, IA 50011-1020