Montastraeidae Family of Star Corals
One Star Coral of the Montastraeidae Family can be found in this website:
Great Star Coral, Montastraea cavernosa. A representative of the Montastraeidae Family of Star Corals.
Phylogeny: Star Corals of the Montastraeidae Family, like hydroids, jellyfish and sea anemones, are members of the phylum Cnidaria. They are in the subphylum Anthozoa, the class Hexacoralia, and the order Scleractinia of stony corals. The Montastraeidae Family is one of twenty four families in the suborder Vacatina. The Montastraeidae Family is very small, with only one genus and one species. The family name Montastraeidae and the genus name Montastraea comes from the Greek words meaning “mountain star” or “starry mountain”. This refers to their massive form being covered with star-shaped corallites.
Morphology: Star Coral polyps have radial symmetry, a hollow digestive cavity, and specialized stinging structures contained within the tentacles surrounding the mouth. Their polyps have a flower-like appearance, representative of the subphylum Anthozoa. As hexacorals, they have six-fold symmetry. In addition, their polyps produce a hard, calcareous skeleton, representative of the order Scleractina. They live in colonies where new generations build upon the skeletons of previous generations, forming coral reefs. Star Corals may grow as boulders or domes, or in deeper water, as plates. The individual corallites may look like volcanos or tubes, depending on the steepness of their profile. The exteriors are sculpted with striations or grooves, giving the base a star shape. The corallites measure 5.5 mm (0.2 inches) to 7.5 mm (0.3 inches) in diameter and are separated from neighboring corallites by 5 mm (O.2 inches) to 9 mm (0.4 inches). Star Coral skeletons show sex-related differences, with females having a less dense skeleton compared to males, which is presumably due to reallocating energy to egg production. Corals in the Montastraeidae Family tend to be gray, brown, yellow, or green in color. Star Corals are fairly massive with boulders and domes reaching 1.5 m (5.0 feet) in diameter.
Habitat and Distribution: Star Corals are found on hard substrates such as rock or reef and can be found to depths up to 95 m (312 feet), though most are found between 10 m (33 feet) and 30 m (98 feet). Star Corals grow throughout most reef environments, and are often the predominant coral at depths of 12 m (40 feet) to 30 m (100 feet). This species is able to dominate other corals in turbid and silty environments due to the sediment rejection capabilities of their shape and their sweeper tentacles, which are able to remove sediments from the polyp surface. Star Corals are a tropical Atlantic species and are found along Mexico’s east coast in the Gulf of Mexico and the Caribbean.
Reproduction: Star Coral colonies are gonochoric (male or female). Reproduction can be asexual, through budding, or sexual. Sexual reproduction is accomplished through broadcast spawning, with external fertilization. The 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. The single new polyp forms a new colony by budding. The polyps deposit calcium carbonate below them thus building on the current structure and forming the large boulder shape the species is known for. Spawning takes place one week after the full moon in late August.
Ecosystem Roles: Star Corals are zooxanthellate. They have a symbiotic relationship with single-cell dinoflagellates, 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. Star Corals supplement the energy provided by zooxanthellae by using their tentacles to capture amphipods and other plankton from the surrounding water. The tentacles then pass the food to the mouth. There is limited documentation of predation related to Star Corals. Some of their known predators include butterflyfish, damselfish, parrotfish, and the Helmet Coral Snail, Coralliophila galea. Star Corals are aggressive at defending their living space from other corals.