Gemmelli’s Jackknife Clam Shell, Solen gemmelli
Gemmelli’s Jackknife Clam Shell, Solen gemmelli. Shell collected off the beach of Punta Chivato, Baja California Sur, March 2025. Size: 5.4 cm (2.1 inches) x 1.0 cm (0.4 inches) x 0.3 cm (0.1 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.
Phylogeny: Gemmelli’s Jackknife Clam, Solen gemmelli (Cosel, 1992), is a bivalve shell that is a member of the Solenidae Family of Jackknife Clams. The genus Solen is one of three genera in this family, and there are sixty-six species in this genus. They are known in Mexico as Almeja Navaja de Gemmell and Tagelo de Gemmell. The word solen comes from the Greek word for pipe, referring to the cylindrical shape of the two valves together. This shell was named in honor of Joyce Gemmell who was an active collector of marine mollusk specimens from the San Felipe, Baja California area between 1964 and 1975.
Description: Gemmelli’s Jackknife Clam Shells have an elongated rectangle to oval profile. When the valves are closed the shell is somewhat cylindrical. Both ends are broadly rounded. The dorsal margin is straight. The ventral margin may be straight or slightly bowed. Shells in this family have only one cardinal tooth per valve. These shells are very thin, to the point of being translucent. They are white and shiny, with pinkish or brownish commarginal growth bands. The periostracum is light yellow, becoming brown toward the anterior end. Gemmelli’s Clams reach a maximum of 6.3 cm (2.4 inches) in length.
Habitat and Distribution: Gemmelli’s Jackknife Clams are found on sand, intertidally and to a depth of 90 m (295 feet). They are a subtropical Eastern Pacific species that have that have a limited range within Mexican waters of the Pacific Ocean being endemic to the northern half of the Sea of Cortez being found as far south as Mulegé, Baja California Sur.
Ecology and Behavior: Gemmelli’s Jackknife Clam is a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Other species in Family Solenidae 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. There is no mention in the available literature of them engaging in any types of parasitic, commensal, or symbiotic relationships. From a conservation perspective they have not been formally evaluated.
Synonyms: None