Posted: Nov 11 2009; Update 8/25/24
Argopecten irradians amplicostatus (Dall, 1898), Texas Bay Scallop
A. irradians has popularly been divided into subspecies. Using Abbott (American Seashells 1974) as a baseline the subspecies names were:
Argopecten irradians irradians (Lamarck, 1819)
Argopecten irradians concentricus (Say, 1822)
Argopecten irradians amplicostatus (Dall, 1898)
The distribution of these three shells is displayed in the below slide. Note that despite the occasional adventitious occurrence of an A. irradians between North Carolina and Palm Beach County, Florida, (see Lee 2009) living populations of the Bay Scallop have not been documented within this “Gap.”
Following is a photo discussion of Argopecten irradians amplicostatus (Dall, 1898) followed by a comparison of all three varieties.
In October 2026 Steve Rosenthal purchased some shells offered as A. amplicostatus. He included LTS as part of a group emailing and commented, "I was a bit skeptical ... I never saw any amplicostatus with any color at all to speak of. " "... they all came from the collection of Jim and Linda Brunner (the Brunner's lived in Panama City FL.)"
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Steve got three informative replies:
Marlo: I count 22 ribs on shell #1, 21 on #2 and 21 on #3. All have ribbing narrower and with narrower interspaces than amplicostatus. And, I agree with you that I’ve never seen orange amplicostatus. My personal reaction is that the data is baloney.
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Les Crnkovic of Texas provided detailed comments based upon his extensive experience collecting this shell:
"Documented Range of: Argopecten irradians amplicostatus
From Galveston, Texas, to Tuxpan, Veracruz, Mexico
About 365 miles Texas Coast, 350 Mexican Coast = Range +/- 715 miles.
Farm raised are usually more colorful, ….but Texas has no Scallop Aquaculture.
In Texas wild caught, if any special coloration, they are typically blushed (yellows to rouge, or yellows to browns) at the beak with very little on the ribs (if any). Color is usually one sided, ventral. But there are always the outliers. I have found some that were overall very citrine. The further south you go the more color potential.
Most of my live collected are from Corpus Christi Bay (which is parallel to Tampa FL), while S. Padre Island Texas is parallel to Naples.
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In Texas worn beach shell coming in from offshore are often full orange to red, and black, but small. I do not know if this is chemically induced postmortem. As such, maybe these are from offshore vs. bays."
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Linda Brunner: "These are all concentricus from St Joseph Bay, FL I know each personally."