In the vast expanse of the ocean, nothing holds greater biodiversity than that of coral reefs. Among these are approximately 6 thousand species of coral, displaying various colors, shapes, and sizes.
Lettuce coral (Agaricia agaricites) is one of these many fascinating lifeforms that form an intricate part of coral reefs around the world. It is known by many other names: Leaf Coral, Purple Lettuce Coral, Scaled Lettuce Coral, Tan Lettuce Leaf Coral, and Thick Lettuce Leaf Coral.
Continue reading as we explore everything this lettuce-like coral has to offer.
Appearance
Lettuce coral is an unusually shaped hard coral that looks somewhat like lettuce leaves. These stony corals grow in various shapes and sizes, depending on the type of water, the depth of the water, and the velocity of water flow in which they live.
A. agaricites has various habits of growth, but the most common is encrusting sheets that form irregular projections or leaf-like plates.
The plates of lettuce coral grow either vertically or horizontally, with the vertical plates containing corallites (polyp cups) on both sides and the horizontal plates containing polyps only on the upper side.
These polyps build the hard, calcium carbonate skeleton that forms the coral’s structure, and they extend their tentacles at night to capture plankton and other small organisms from the surrounding water.
Tan lettuce-coral, as mentioned above, can be found in various colors, ranging from greenish brown, yellow, and light brown, or brown with a purple shade.
Lettuce coral varies in size, with its colonies typically reaching diameters of 8 to 16 inches (20 to 40 cm).
The colony’s overall shape contributes to its lettuce-like appearance, with the laminae (the plates of the coral) mimicking the texture and form of lettuce leaves.
Did you know…
Lettuce coral exhibits a remarkable adaptation called fluorescence. Under certain light conditions, particularly blue or ultraviolet light, it can emit vibrant, glowing colors, ranging from green and yellow to orange and red. While the exact function of this fluorescence is still being researched, it’s thought to play a role in protecting the coral from harmful solar radiation, attracting symbiotic algae, or even enhancing photosynthesis in its symbiotic algae.
Habitat
Lettuce coral thrives in shallow, tropical shallow waters, predominantly inhabiting the Caribbean Sea and the western Atlantic Ocean.
Its range spans an area of 2,500,000 square kilometers from the Caribbean Sea to the East Brazil Shelf and can be found in the waters of the Gulf of Mexico, the Caribbean Sea, Florida, the Bahamas, the Fernando de Noronha Islands, and the Rocas Atoll.
The coral has remarkable adaptability to various environments and can be found living on rocky substrates, coral reefs, and other solid marine surfaces in lagoons, channels, and even seagrass meadows.
It prefers waters with a moderate flow and a large amount of sunlight and can be found growing on fore reefs, back reefs, and reef platforms. When these criteria is met, they can be found growing at depths from 3 feet (1 meter) all the way down to 246 feet (75 meters).
Brown colonies of tan lettuce-leaf coral are more common in deeper habitats, typically below 30 meters, while orange colonies are more common between 5 and 30 meters.
It’s also worth noting that lettuce coral has been observed to change shape and structure as depths increase.
Diet
As a member of the cnidarian family, lettuce coral, similar to other cnidarians such as jellyfish and sea anemones, makes use of tentacles with stinging cells known as nematocysts. These tentacles play an important role in capturing and immobilizing prey.
When night falls, the coral extends their tentacles and filters the water for passing plankton, zooplankton, and other microscopic organisms.
When food is scarce or water flow is too high, lettuce coral withdraws their tentacles to conserve energy and for protection.
That said, lettuce coral is a zooxanthellate species, meaning they contain single-celled dinoflagellates. This symbiotic relationship allows the coral to draw energy in from the photosynthesizing cells of the algae, providing it with 70% to 90% of its energy requirements.
Reproduction
Agaricia agaricites can reproduce both asexually by fission and sexually. Asexual reproduction occurs through budding, where new polyps sprout from established ones, branch off, and eventually disconnect from new colonies. This method of asexual reproduction is rapid and allows the coral to colonize new territories at an accelerated rate.
Sexual reproduction in A. agaricites is an annual event and occurs during spring and summer when the coral sheds their planulae larvae. This release of gametes is timed with the lunar cycle, and when eggs and sperm meet, planula larvae are formed. These larvae drift in the ocean’s currents before settling onto a suitable substrate and metamorphosing into polyps. These polyps then begin secreting their calcium carbonate skeletons, which begin to form the start of a new stony coral reef.
Threats
Despite the inherent resilience and adaptability of tan lettuce-leaf coral, the species remains at risk from numerous environmental and human-induced factors.
This stony coral is extremely sensitive to environmental conditions, such as the intensity of light and oceanic currents.
When these conditions become harsh, the coral has been known to develop a crust over its free edges. In rough waters, the colonies grow much smaller and have a spherical shape, which helps protect them from fast-moving currents.
When conditions are not ideal, lettuce coral deploys various means of defense. When confronted with stressors like rising water temperatures, lettuce coral may expel its symbiotic algae, a phenomenon known as coral bleaching.
A. agaricites is extremely susceptible to bleaching, and during the mass bleaching event of 1997 due to El Niño, lettuce coral was found to be the most affected species off the coast of Brazil.
During this time, nearly 80% of the species was affected by bleaching and was one of the slowest coral species to bounce back from the event.
Apart from expelling its symbiotic algae, lettuce coral produces natural compounds that deter predators and competitors.
Some species that commonly feed on lettuce coral include parrotfish, invertebrates, wrasse, sea urchins. Additionally, the population of A. agaricites is threatened by human-induced factors such as overfishing, habitat destruction, pollution, and rising water temperatures due to climate change and global warming.
Facts about lettuce coral
- These corals can grow quite large, forming expansive, leafy structures up to several feet across.
- It’s a relatively peaceful coral, meaning it doesn’t have long, sweeper tentacles to sting neighboring corals.
- Lettuce coral comes in a variety of colors, including shades of green, brown, purple, and even fluorescent hues.
- It’s a popular choice for reef aquariums due to its hardiness and beautiful appearance.
- While it primarily relies on photosynthesis from its symbiotic algae, lettuce coral can also capture and consume small plankton.
FAQs
How does lettuce coral get its vivid colors?
The vibrant colors of lettuce coral are derived from pigments within its zooxanthellae, the algae that aid it in photosynthesis.
Is lettuce coral a solitary organism or a colony?
Lettuce coral forms colonies comprising numerous individual polyps, each contributing to the coral’s structure and functionality.
What role does lettuce coral play in the ecosystem?
Lettuce coral serves as an essential habitat and refuge for diverse marine organisms, fostering biodiversity and coral reef health.
How can I contribute to the protection of lettuce coral and coral reefs?
You can make a positive impact by adopting sustainable practices, such as reducing carbon emissions, advocating against destructive fishing methods, and supporting marine conservation initiatives.
