Comprehensive Description

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Biology/Natural History: This abalone can grow to larger size than any other abalone in this area. Abalones are algae grazers; mostly on microalgal films on the rocks though adults also capture pieces of kelp with their foot and consume them. The red color in the shell comes from rufescine; which is similar to the phycoerythrin found in red algae. If the abalone has been feeding primarily on brown algae the shells are aquamarine, green, or white instead of red. A diet alternating between red and brown may give a banded shell. Boring sponges (Cliona celata) often inhabit the older portions of the shell. The small boring clam Penitella conradi may bore into the shell from the outside, causing the abalone to secrete an extra blister of nacre inside to keep the clam from bursting through. The tissue of the foot is often iridescent, and the tentacles are black. This species becomes sexually mature at 6 years, and may live for 20 years. They spawn throughout the year, especially February to April. A large female may have over 12 million ripe oocytes. The veliger larvae are induced to settle by compounds released from coralline algae, jpon which the young abalones graze. This species is commercially the most important, and is commonly served in restaurants. They are also prized by otters, rock crabs Cancer antenarius, octopus, and the seastars Pycnopodia helianthoides and Pisaster ochraceous. They exhibit an galloping, zigzag escape response from predatory seastars, with the upper part of the foot extended over the edge of the shell. Adult abalones occupy a home scar and do not range far. Fossils of abalone are found in Cretaceous strata. They exist in several oceans but grow to largest size in the Pacific. The swimming veliger larvae chew on coralline algae, which releases GABA (gamma-aminobutyric acid). This chemical induces the veligers to settle and metamorphose into juveniles. The abalone scrapes only the surface off the coralline algae, so it actually benefits the algae by removing fouling epiphytes. The animal obtains a red dye (rufescin) from the algae, which it incorporates into its shell for the pink color. The color probably helps camouflage the abalone from predators such as octopus.


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© Rosario Beach Marine Laboratory

Source: Invertebrates of the Salish Sea

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