Wavy Turban Shell, Megastrea undosa

Wavy Turban Shell, Megastraea undosa. Shell collected off the beach of Punta Chivato, Baja California Sur, March 2024. Size: 6.2 cm (2.4 inches) x 7.2 cm (2.8 inches) in diameter. Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Wavy Turban Shell, Megastraea undosa. Shell courtesy of the commercial fishermen of the greater Los Cabos area, March 2013. Size: 8.2 cm (3.2 inches) x 7.4 cm (2.9 inches).

Wavy Turban Shell, Megastraea undosa. Shell collected off the beach of San Juanico, Baja California Sur, March 2022. Size: 8.7 cm (3.4 inches) x 9.9 cm (3.9 inches) in diameter. Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Phylogeny: The Wavy Turban Shell, Megastraea undosa (W. Wood, 1828), in a gastropod mollusk that is a member of the Turbinidae Family of Turban Shells. The genus Megastrea is one of eighteen genera in this family, and there are only two species in this genus.  They are also known as the Waxy Top Shell and the Wavy Top Shell, and in Mexico as Caracol Panocha. The species name undosa comes from the Latin words meaning “abounding in waves”, referring to this shell’s wavy texture.

Description: Wavy Turban Shells are large, solid and wider than they are tall. They consist of six to eight sloping whorls that are separated by wavy sutures. The exterior is additionally sculpted by wavy diagonal ridges. The exterior of the shell is tan or brown in color. The interior is pearly white. They have a thick, ridged, operculum, and a dark, fibrous, periostracum. Wavy Turban Shells reach a maximum of 15 cm (5.9 inches) in diameter.

Habitat and Distribution: Smaller Wavy Turbans are found on rocks just below the intertidal zone. Larger specimens are found in rocky or shale areas, often in Kelp Forests, to depths up to 23 m (75 feet). They are a subtropical Eastern Pacific species  that are found in Mexican waters of the Pacific Ocean on a limited basis being found north of Bahía San Juanico, Baja California Sur, along the central and northwest coasts of the Baja Peninsula.

Ecology and Behavior: While most turban shells are herbivores, Wavy Turban Shells differ being omnivores. Their diets consist of algae, surf grass, and invertebrates such as hydroids and isopods. In turn they are preyed upon by fishes, Kellet’s Whelks, lobsters, octopuses and sea stars. They are gonochoric and reproduce sexually, with external fertilization. The eggs are laid as a gelatinous mass. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective the Wavy Turbans 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: Astraea undosa, Lithopoma undosum, and Trochus undosus.