Panamic Comb Venus Clam Shell, Hysteroconcha lupanaria

Panamic Comb Venus Clam Shell, Hysteroconcha lupanaria. Shell collected within Magdalena Bay, Baja California Sur, October 2019. Size: 7.6 cm (3.0 inches) x 3.9 cm (1.5 inches) including spines. Identification courtesy of Bob Hillis, Ivins, Utah.

Panamic Comb Venus Clam Shell, Hysteroconcha lupanaria. Shell collected off the beach of San Juanico, Baja California Sur, February 2023. Size: 7.9 cm  (3.1 inches) x 6.1 cm (2.4 inches) x 4.1 cm (1.6 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Panamic Comb Venus Clam, Hysteroconcha lupanaria (R. P. Lesson, 1831), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Hysteroconcha is one of one hundred seven genera in this family, and there are five species in this genus.

Description: The Panamic Comb Venus Clam Shell is trigonal in outline, with two rows of straight to slightly curved spines projecting from the posterior of the shell. Often, some or all of the spines have broken off, especially along the row closest to the posterior margin. The shell is fairly thick and moderately inflated with the exterior being sculpted with numerous commarginal ribs. The exterior of the shell is cream, tan or lavender in color with brown or purple hues that are most pronounced at the base of the spines. The interior is white or brown with purple blotches. These shells are covered with a thin, silky periostracum. Panamic Comb Venus Clam Shells reach a maximum of 7.8 cm (3.1 inches) in length and 4.1 cm (1.6 inches) in height.

Habitat and Distribution: Panamic Comb Venus Clams are found in sand substrate in the intertidal zone, and to depths up to 25 m (82 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exceptions that they are absent from north of Punta Pequeña, Baja California Sur, along the central and northwest coasts of the Baja Peninsula and north of  Bahía Kino, Sonora, in the Sea of Cortez.

Ecology and Behavior:  Panamic Comb Venus Clams are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. Their commensal, parasitic, commensal, or symbiotic relationship have not been formally documented.  From a conservation perspective they have not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: Cytherea lupanaria, Cytherea semilamellosa, Dione exspinata, Pitar lupanaria, and Venus lupanarian.