Owl Limpet Shell, Lottia gigantea
Owl Limpet Shell, Lottia gigantea. Shell collected off the beach in the greater Agua Verde area, Baja California Sur, April 2018. Size: 8.0 cm (3.1 inches) x 6.0 cm (2.4 inches). Collection and photographs courtesy of Barry Mastro, Escondido, California.
Phylogeny: The Owl Limpet, Lottia gigantea (G.B. Sowerby I, 1834), is a gastropod mollusk that is a member of the Lottiidae Family of True Limpet Shells. The genus Lottia is one of fifteen genera in the family, and there are sixty-five species in this genus. They are also known at the Giant Owl Limpet and in Mexico as Lapa Gigante.
Description: The Owl Limpet shell is large with an oval profile that has a low, frequently eroded, apex at the anterior end. The exterior surface is rough. The outside of the shell is mottled brown and whitish in color. The brown areas are raised over the lighter areas, often in a radial pattern, and most apparent toward the margin. The interior is glossy with a bluish center, sometimes with brown blotches and a black margin. The outline of the bluish center resembles the outline of a Great Horned Owl, giving rise to its common name. Owl Limpet Shells reach a maximum of 12.1 cm (4.8 inches) in length and 9.1 cm (3.6 inches) in height. Females of this species are larger than the males.
Habitat and Distribution: Owl Limpets are found attached to wave-swept rocks in the mid to upper intertidal zone and they are often associated with mussel beds. They are a temperate to subtropical Eastern Pacific species that are found in Mexican waters of the Pacific Ocean within a limited range. They are found along the west coast of the Baja Peninsula from the California border south to San Ignacio Lagoon, Baja California Sur. They have not been found in the Sea of Cortez.
Ecology and Behavior: Owl Limpets are herbivorous grazers that feed primarily on algae. They are nocturnal and return to their home scar on the rock during the day. Females may keep an algae garden territory of up to 1000 square cm (155 square inches). Owl Limpets aggressively defend their grazing territory from other shell species. They use their mass to shove other species away or they clamp their shell down on the foot of other snails causing the withdrawal of the foot, loss of suction and subsequently to being swept away by wave action. Owl Limpets are prey for other gastropods, shore birds such as the Black Oystercatcher, and sea stars such as the Ochre Starfish, Pisaster ochraceus. Owl Limpets are sequential hermaphrodites, beginning life as a male and, once they have matured and established their own territory, becoming female. They reproduce sexually, through broadcast spawning, with external fertilization. Reproduction occurs during high tides in January and February. Males become sexually mature at two to three years of age and females at three years of age. They can live for twenty years. Owl Limpets have a symbiotic relationship with the algae that they eat. They protect it from other species and as they graze, they lay down a mucous trail that fertilizes the algae. Owl Limpets sometimes host the smaller Rough Limpet Collisella scabra as an epibiont. Owl Limpets are edible and have been collected artisanally, commercially, and recreationally for food and fish bait. Over collecting has seriously impacted population levels in localized areas. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.
Synonyms: None