Mexican Dancer, Elysia diomeda
Mexican Dancer, Elysia diomedea. Sea slug photograhed in it’s native environment in coastal waters off San Carlos, Sonora, April 2025. Photograph and identification courtesy of Dr. Jake Turin, Albuquerque, New Mexico.
Mexican Dancer, Elysia diomedea. Sea slug collected at Km 17, El Tule, Baja California Sur, November 2011. Length: 2.6 cm 1.0 inch).
Mexican Dancer, Elysia diomedea. Underwater photographs taken in Zihuatanejo Bay, Guerrero, February 2020 and January 2022. Photograph and identification courtesy of Maude Jette, Dive Zihuatanejo, www.Divezihuatanejo.com.
Mexican Dancer, Elysia diomedia. Underwater photographs taken in Zihuatanejo Bay, Guerrero, January and February 2023. Underwater photographs taken in Zihuatanejo Bay, Guerrero, in February 2022. Photographs courtesy of Ron Woheau, Zihuatanejo.
Phylogeny: The Mexican Dancer, Elysia diomedia (Bergh, 1894), is a member of the Plakobranchidae Family of Sea Slugs. The Elysia genus is one of four genera in the Plakobranchidae Family, and there are one hundred three species in the Elysia genus. They are also known as Diomede’s Sapsucker and in Mexico as Babosa Marina, Bailarina Mexicana, and Danzarina Mexicana. They are a sister species of the Lettuce Sea Slug, Elysia cirspata, found in the Caribbean, which were believed to be one and the same species until the Panama land bridge closed and they evolved into separate species. The genus name Elysia comes from the Greek words used for heaven or paradise in Greek mythology. The species name diomedia comes from the Greek words meaning “divine advice” or “divine plan”. Both of these names reflect the exquisite beauty of this species.
Morphology: The Mexican Dancer has an oval outline with a relatively high profile. They have frilled parapodial lobes on their dorsal surface. Mexican Dancers vary in color depending on the location, depth and light conditions but are generally green to greenish-brown in color. They have broken white lines running parallel to the long axis of the body, small blue spots scattered over the dorsum and the inner walls of the parapodium, and a border of black spots. The fringes of the frilled parapodium may be orange, pink, white or yellow. The rhinophores are marked with black and yellow to white bands. Mexican Dancers reach a maximum of 7.5 cm (3.0 inches) in length.
Habitat and Distribution: The Mexican Dancer is found on and under rocks and within reefs from the intertidal zone to depths up to 23 m (75 feet). They are a subtropical to tropical Eastern Pacific species. In Mexican waters the Mexican Dancer is found throughout the Gulf of California and ranges south to Guatemala. It is absent from the west coast of the Baja Peninsula. This species is the most common opisthobranch on the west coast of Mexico and Central America.
Diet: Mexican Dancers feed on algae, by piercing and sucking out the insides of algae cells. They are also “Solar Sea Slugs”, retaining living chloroplasts in their tissue, which continuously photosynthesize and provide the sea slug with sugars for its own nutrition. This process of incorporating chloroplasts into their cells is known as kleptoplasty. This requires that Mexican Dancers remain in relatively shallow water to have sufficient sunlight for photosynthesis to occur.
Predators: Mexican Dancers are preyed upon by a sea slug known as the Enigmatic Navanax, Navanax aenigmaticus.
Reproduction: Mexican Dancers are simultaneous hermaphrodites (having both male and female reproductive organs). Reproduction is sexual with internal fertilization. The fertilized eggs are laid, by the thousands, in a flat spiral ribbon. The eggs hatch into veliger larva and remain in a planktonic state for some time before metamorphosing into their benthic adult state.
Ecosystem Interactions: Mexican Dancers have an endosymbiotic relationship with the algae that they incorporate into their body cells through kleptoplasty. There are no other documented commensal, parasitic or symbiotic relationships.
Human Interactions: Mexican Dancers have a very limited direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.
Synonyms: Tridachia diomedia and Tridachiella diomedia.