Renillidae Family of Sea Pansies

One Sea Pansy of the Renillidae Family can be found in this website:

Purple Sea Pansy, Renilla amethystina. A representative of the Renillidae Family of Sea Pansies.

Phylogeny: Sea Pansies are an octocoral member of the Renillidae family and like hydroids, jellyfish and sea anemones they belong to the phylum Cnidaria.  They are the subphylum Anthozoa, the class Octocorallia, the order Scleralcyonacea, and the superfamily Pennatuloidea. The Renillidae family is one of sixteen families in this superfamily. The Renillidae family is small and contains only one genus and six species. The name Renillidae comes from the Latin word meaning “kidney”, and refers to the kidney-shaped appearance of species in this family. Their common name Sea Pansy refers to their resemblance to the common pansy found in domestic flower gardens.

Morphology: As Cnidarians, Renillid Sea Pansies have polyps with radial symmetry, a hollow digestive cavity, and specialized stinging structures in tentacles surrounding the mouth. Their polyps have a flower-like appearance. As octocorals, they are colonial organisms, with polyps that have 8-fold radial symmetry. Their 8 tentacles are pinnate (having a feather-like appearance). Octocorals lack the hard calcium carbonate skeletons of stony corals. Sea Pansy colonies of the Renillidae Family differ from other octocorals in that they consist of a single large polyp (initial polyp or oozooid) that anchors the colony in soft substrate. This oozooid supports the feeding polyps (autozooids) and water circulation polyps (siphonozooids), which are located on the disk.  The anchoring stalk has an axis composed primarily of calcium carbonate.  Sea Pansies look like fleshy, purple, water lilies. The have a heart-shaped, or round, disk, anchored to the bottom by a stalk. The disk reaches about 12.7 cm (5.0 inches) in diameter and the stalk about 10 cm (3.9 inches) in length.

Habitat and Distribution: Sea Pansies are found on sandy bottoms. 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 predation by nudibranchs and sea stars that also are threatened by turbulence.  Sea Pansies are found at depths up to 150 m (492 feet). They are found worldwide in temperate to tropical seas. At least two species from this family are found in Mexican waters.

Reproduction: Renilllid Sea Pansy colonies are gonochoric (male or female for life). They reproduce sexually, through broadcast spawning, with external fertilization. Mature gametes are released into the coelenteron and spawned through the mouth. The eggs develop into planular larvae before they settle to the substrate and metamorphose into their adult form. They may also reproduce asexually, by budding.

Ecosystem Roles:  Sea Pansies are suspension feeders that use their stinging polyps to capture suspended prey that becomes ensnared in the mucous web secreted by the animal. In turn they are preyed upon by nudibranchs and sea stars.