Smooth Flower Coral, Eusmilia fastigiata

Smooth Flower Coral, Eusmilia fastigiata. Underwater photographs taken in the coastal waters off Bonaire, Caribbean Netherlands, December, 2019. Photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Smooth Flower Coral, Eusmilia fastigiata. Featured on a postal stamp of Belize.

Phylogeny: The Smooth Flower Coral, Eusmilia fastigiata (Pallas, 1766), is a hexacoral in the Meandrinidae Family of Flower Corals. The genus Eusmilia is one of four genera in this family. This is the only species in the Eusmilia genus.

Morphology: Smooth Flower Coral polyps have radial symmetry, a hollow digestive cavity, and specialized stinging structures in tentacles surrounding the mouth. Their polyps have a flower-like appearance and produce a hard, calcareous skeleton. Their colonies are usually dome shaped, with tall, widely spaced, tubular corallites. The septa are evenly spaced, and alternating. This species has well developed costae (ribs). The tentacles are of two sizes. The corallites can be solitary or branch into groups of two or three. The corallites are connected by a layer of translucent, jelly-like mesoglea tissue called coenosarc which covers the surface of the calcium carbonate skeleton.  Flower Corals are yellow brown to grey in color, often with a bluish or greenish tint. The polyp tentacles are white. The corallites can reach 25 cm (9.8 inches) in height, but most are much smaller.

Habitat and Distribution: The Smooth Flower Coral is found on reefs and shelves at depths up to 60 m ( 200 feet), though it is most common between 5 m (16 feet) and 30 m (98 feet). Smooth Flower Coral is a tropical Western Atlantic species that is found in Mexican waters of the Gulf of Mexico and the Caribbean, ranging from Tampico, Tamaulipas to Belize.

Diet: Smooth Flower 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.

Predators: There is limited documentation of predation related to Smooth Flower Coral. However they are known to be preyed upon by the Threespot Damselfish, Stegastes planifrons and the Stoplight Parrotfish, Sparisoma virde.

Reproduction:  Smooth Flower Coral polyps can be either gonochoric (male or female for life) or hermaphroditic (having both male and female reproductive organs). Reproduction can be asexual, through  budding, or sexual. Sexual reproduction occurs through broadcast spawning, with internal fertilization. Mature gametes are shed into the coelenteron and spawned through the mouth. The zygote develops into a planktonic planula larva. Metamorphosis begins with early morphogenesis of tentacles, septa and pharynx before larval settlement on the aboral end.

Ecosystem Interactions: Smooth Flower Coral are known to host parasitic Apicomplexan Corallicolids. It is also susceptible to White Plague, a disease caused by an unknown pathogen. Other than the symbiotic relationship with zooxanthellae, there are no other documented interspecies relationships.

Human Interactions: Smooth Flower Corals have limited direct impact on human activities. They are impacted by water pollution and disease. From a conservation perspective the Smooth Flower Coral is currently considered to be Critically Endangered.

Synonyms: Caryophyllia fastigiata, Eusmilia alticostata, Eusmilia aspera, Eusmilia fastigiata f. fastigiata, Eusmilia fastigiata f. flabellata, Eusmilia fastigiata f. guacanayabensis, Eusmilia fastigiata f. typica, Eusmilia knorri, Eusmilia knorrii, Eusmilia silene, Lithodendron capitatum, Lithodendron fastigiatum, Lobophyllia fastigiata, Madrepora capitata, and Madrepora fastigiata.