Purple Sea Pansy, Renilla amethystina

Phylogeny:  The Purple Sea Pansy, Renilla amethystina (Verrill, 1864) or Renilla koellikeri (Pfeiffer, 1886)  is an octocoral the Renillidae family of Sea Pansies. Renilla is the only genus in this family, and there are six species in this genus. In the popular scientific literature as well as internet sources there is little distinction made between Renilla amethystina  and Renilla koellikeri which are used synonymously. Guide book photos and on-line images of the two species are sometimes identical, as are the physical descriptions and geographic ranges. The World Registry of Marine Species (WoRMS) list these two species as separate and not synonymous. In Mexico they are known as Oreja de Negro and Renilla Flor Púrpura. The genus name Renilla refers to the kidney shape that many sea pansy species exhibit.

Morphology: Purple Sea Pansies differ from most octocorals in that they consist of a single large polyp (initial polyp or oozooid) that anchors the polyp in soft substrate. This oozooid supports the feeding polyps (autozooids) and water circulation polyps (siphonozooids).  Both the amethystina and koellikeri species have flattened, heart-shaped discs. The discs are purple, with translucent white polyps. Often, the disc is partially covered by sand. The anchor stalk is fleshy. The discs reach a maximum diameter of 12.5 cm (5”). They can display a greenish bioluminescence if disturbed at night.

Habitat and Distribution: The Purple Sea Pansy resides on sand or mud substrates, between the low intertidal zone and depths up to 56 m (184 feet) . They are often found in a relatively narrow band because of depth requirements. They need to be in deep enough water to avoid being torn loose by surf or surge, but shallow enough to avoid predators that also are threatened by turbulence. Because of the confusion over the naming of this species, it is difficult to determine its geographic range. Some sources say it is found in both the Atlantic and Pacific oceans. Documented observations seem to limit the range to the Eastern Pacific. In Mexican waters they are found along the entire West Coast of the Baja.  We have a report that they have also been found within Kino Bay in the northern Sea of Cortez.

Diet: Purple Sea Pansies feed on small animals and larvae, stinging and swallowing them after they become entangled in a mucous net secreted over the dorsal surface of the sea pansy. Food is first digested by septal filaments followed by intracellular digestion.

Predators: The Purple Sea Pansy is preyed upon by the Spiny Sand Star, Astropecten armatus  and the Striped Nudibranch,  Armina californica.

Reproduction:  Purple Sea Pansies are gonochoric (male or female for life). They reproduce asexually, through budding, or sexually through broadcast spawning, with external fertilization. The fertilized eggs hatch into planktonic larvae, which eventually settle to the substrate and begin their benthic life.

Ecosystem Interactions: There is no documentation of Purple Sea Pansies engaging in any types of commensal, parasitic, or symbiotic relationships.

Human Interactions: Purple Sea Pansies have no 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:  None.