Swainson’s Miter Shell, Isara swainsonii
Swainson’s Miter Shell, Isara swainsonii. Shell courtesy of the commercial fishermen of the greater Los Cabos area, Baja California Sur, February 2010. Size: 9.4 cm (3.7 inches) x 2.1 cm (0.8 inches).
Phylogeny: Swainson’s Miter Shell, Isara swainsonii (Broderip, 1836), is a gastropod mollusk that is a member of the Mitridae Family of Miter Shells. The genus Isara is one of thirty-six genera in this family, and there are thirty-two species in this genus. They are also known as the Antillean Miter Shell. This shell was named in honor of the British ornithologist, malacologist, conchologist, entomologist, botanist, and artist William Swainson, for whom many species of animal are named.
Description: The Swainson’s Miter Shell is large and fusiform (spindle-shaped). They consist of seven to eight flat-sided whorls. The body whorl is longer than the spire. The shell is sculpted with fine spiral lines. The aperture is long and fairly straight. The inner lip is marked with three folds. The exterior of the shell is cream to buff in color and they are covered with a thin, very dark, periostracum. The interior is white. Swainson’s Miter Shells reach a maximum of 16.5 cm (6.5 inches) in length and 9.4 cm (3.7 inches) in height.
Habitat and Distribution: Swainson’s Miter Shell are found on sand and mud, at depths of 5 m (15 feet) to 79 m (260 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from the west coast of the Baja Peninsula and from north of Cabo San Miguel, Baja California, in the Sea of Cortez.
Ecology and Behavior: Swainson’s Miter Shell are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Some sources report that all species in the Mitridae Family feed exclusively on Sipunculids (Peanut Worms), while other sources include other crustaceans, mollusks and worms They are gonochoric and reproduce sexually, with internal fertilization. The eggs are laid in protective capsules. They’re engagement in any type of commensal, parasitic, or symbiotic relationships has not been formally documented. From a conservation perspective Swainson’s Miter has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.
Synonyms: Mitra swainsoni ,Mitra (fusimitra) swainsoni, Mitra zaca, and Strigatella (Atrimitra) mexicana.