Southern Quahog
Mercenaria campechiensis
Morphology 2
The overall shape is ovate, with a rounded anterior margin and a lightly pointed posterior margin. The valves are the same size and shape (equivalve), and there is no gape when they are closed. The valves are ornamented with growth lines and comarginal ribs. As the animal grows, the ribs become denser and finer. The lunule is impressed and heart-shaped, and it extends approximately half of the anterior dorsal margin. The umbo points anteriorly and projects dorsally. The escutcheon is impressed and covers the posterior dorsal margin; its width is approximately 1/4th of its length.
The exterior color is white or light tan, but other details vary. Some shells have a light brown zig-zag pattern. The escutcheon may be a dark brown. There may be comarginal dark lines. The interior color is white. There is sometimes purple coloration along the interior margin.
The ligament is exterior and extends half of the posterior dorsal margin. The nymph supports the ligament and has a rugose texture. There are three cardinal teeth on each valve. On the left valve, the central tooth is bifid, the anterior can be slightly bifid, and posterior teeth are not bifid. The posterior tooth has merged with the nymph. On the right valve, the central and posterior teeth are bifid and the anterior tooth is not. There are no lateral teeth. There are crenulations on the interior shell margin. The anterior and posterior adductor muscle scars are similar in size and shape. The pallial sinus is tapering and shallow.
Look alikes 3
Similar to Mercenaria mercenaria. Mercenaria campechiensis can be distinguished by the ribs, which become more dense and fine as the animal grows; whereas, Mercenaria mercenaria is distinguishable by a central smooth region on the valves, with stronger ribs anteriorly and posteriorly.
Similar to Pitar morrhuanus. Mercenaria campechiensis is distinguishable by its lack of lateral teeth and its posterior tooth (4b) on the left valve, which is fused with the nymph.
Link to Access Genomic Data 4
http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=115816&lvl=0
Sources and Credits
- (c) Victor W Fazio III, some rights reserved (CC BY-NC-ND), uploaded by Victor W Fazio III
- Adapted by matbio from a work by (c) Anderson, Katherine, some rights reserved (CC BY-NC), http://eol.org/data_objects/17784670
- Adapted by matbio from a work by (c) Anderson, Katherine, some rights reserved (CC BY-NC), http://eol.org/data_objects/17784669
- (c) Emily Rose Sharkey, all rights reserved
