Elliptical Star Coral, Dichocoenia stokesi
Elliptical Star Coral, Dichocoenia stokesii. Underwater photograph taken in coastal waters off Cozumel Island, Quintana Roo, March 2021. Photograph courtesy of Marina Sutormina, Stockholm, Sweden. Identification courtesy of Mark Walenta, Miami, Florida.
Phylogeny: Elliptical Star Coral, Dichocoenia stokesii (Milne, Edwards, & Haime, 1849) is a member of the Meandrinidae Family of Stony Corals. They are also known as the Pancake Star Coral and the Pineapple Coral. The Dichocoenia Genus is one of four genera in the Meandrinidae Family, and this species is the only species in the Dichocoenia Genus. The genus name Dichocoenia comes from the Greek words combining “two”, “double”, or “divided” with the words for “communal” or “shared”. This name refers to the double-walled corallites (skeletal cups). This species was named in honor of Admiral John Lort Stokes, a British explorer and surveyor who had been a shipmate with Charles Darwin on the HMS Beagle.
Morphology: Elliptical Star Coral forms massive colonies that may be spherical or plate-like. The individual corallites (cups that house the polyps) have raised rims and may be circular, oval, elliptical patterns, or Y-shaped. The corallites are large and can reach 5 cm (2 inches) in length. The polyps are well separated and reach 4 mm (0.16 inches) in diameter. The color of Elliptical Star Coral can be brown, cream, green, olive, orange, white, or yellowish-brown, with white corallite rims. Spherical colonies can reach a maximum of 40 cm (16 inches) in diameter.
Habitat & Distribution: Elliptical Star Coral is found on hard substrates at depths of 2 m (6 feet) to 72 m (236 feet). It is a tropical Western Atlantic species. In Mexican waters it ranges from Tampico, Tamaulipas, to Belize.
Diet: Elliptical Star Corals are zooxanthellate. They have a symbiotic relationship with single-cell dinoflagellates, also known as zooxanthellae. Zooxanthellae live within certain coral polyps, sea anemones, jellyfish, and nudibranchs. The zooxanthellae produce energy, during daylight, by means of photosynthesis. This energy is passed along to their hosts, sometimes providing up to 90% of the host’s total energy needs. In return, the host provides nutrients, carbon dioxide, and a secure, sunlit, platform for the zooxanthellae. Smooth Flower Corals supplement the energy provided by zooxanthellae by using their tentacles, at night, to capture amphipods and other plankton from the surrounding water. The tentacles then pass the food to the mouth.
Predation: Elliptical Star Corals are preyed upon by fish, gastropods, sea stars, and polychaete worms.
Reproduction: Elliptical Star Coral is gonochoric, and it has the ability to reproduce both sexually, via spawning, or asexually, via budding. Sexual reproduction occurs when separate colonies release gametes into the water and the sperm fertilizes the eggs, resulting in a juvenile larval form
Ecosystem Interaction: Elliptical Star Corals have a symbiotic relationships with single-celled green zooxanthellae algae that live within their tissues. Zooxanthellae feed on the nitrogenous waste from the coral while supplying it with the organic products of photosynthesis. Elliptical Star Coral is highly susceptible to the unknown pathogen (bacteria?) that causes Stony Coral Tissue Loss Disease (SCTLD). It is also known to host endo parasitic protozoans and ecto parasitic sponges. The structure of this coral provides shelter for crustaceans, fish and other invertebrates.
Human Interactions: Elliptical Star Corals have a limited impact on human activities. From a conservation perspective the Elliptical Star Coral is currently considered to be Vulnerable. However, some local populations are considered to be Critically Endangered due to hurricane damage and/or Stony Coral Tissue Loss Disease (SCTLD).
Synonyms: Astraea (Fissicella) porcata, Astraea porcata, Astrea porcata, Dichocoenia cassiopea, Dichocoenia elliptica, Dichocoenia equinoxialis, Dichocoenia pauciflora, Dichocoenia porcata, Dichocoenia pulcherrima, Dichocoenia stellaris, Dichocoenia stokesi, Dichocoenia stokesi f. stellaris, Dichocoenia stokesi f. stokesi, Diploria stokesii, Favia porcata, Madrepora porcata, and Matrepora porcata.