Went snorkeling and saw coral colonies with sun-like yellow tentacles, like on dock pillars or a shipwreck? You may just have run into the orange cup coral. Though beautiful to look at, this species is also highly invasive and can cause damage to native coral populations in areas like the Caribbean Sea.
Want to know more? Below, you’ll find everything you need to know about orange cup coral!
| Name (common, scientific) | Orange cup coral, orange sun coral, Tubastraea coccinea |
| Family | Dendrophylliidae |
| Spread | Indo-Pacific (native), Atlantic, Mediterranean (invasive) |
| Habitat | Reefs, man-made structures |
Orange cup coral appearance
Tubastraea coccinea, better known as the orange cup coral, is a hard type of coral known as a large-polyp stony coral. It has an internal skeleton made of calcium carbonate. The species is one of eight in its genus, which is known collectively as the “sun corals”.
Orange cup coral is easy to recognize. The button-like polyps, up to 2″ each, somewhat resemble mini anemones and grow in colonies of up to 5,5″ across.
During the day, the polyps, which are pinkish-orange in color, are usually closed. At night, they open up to reveal a wreath of yellow-to-orange tentacles.
Note: The common name “orange cup coral” is not exclusive to today’s subject. Another coral, scientifically known as Balanophyllia elegans, is often referred to using the same name. That’s why scientific denominations come in handy!
Orange cup coral natural habitat
Range
Orange cup coral is naturally found throughout much of the Indo-Pacific. Its type locality (the location where the first described specimen was found) is Bora Bora in French Polynesia.
Unlike many other corals, which grow on rocks and the reef floor, orange cup coral particularly likes artificial substrates, such as oil rigs and the like. It doesn’t mind growing vertically or upside-down at all.
Because this species is azooxanthellate, meaning it doesn’t rely on algae in its tissues to photosynthesize, it can grow at great depths where very little light penetrates. Despite the darkness and low temperatures, it feels just as at home in the sub-tidal zone as it does 400ft down!
If this coral sounds like a rather versatile species to you, you’d be right. Which unfortunately leads us to the following…
Invasive species
Orange cup coral is known for its huge invasive potential. It has already successfully managed to establish itself around the world, displacing native corals along the way. This is thought to happen as a result of oil rigs and ships, including their encrusted coral populations, being moved around the world.
Researchers have found orange cup coral in a wide range of different places:
Unfortunately, these studies also reveal that the presence of Tubastraea species does affect local coral populations. For example, there’s solid evidence suggesting it has the potential to outcompete local species like Mussismilia hispida along the Brazilian coast.
How does orange cup coral displace native corals? Well, what a lot of people don’t know is that corals are actually rather aggressive organisms! They all compete for the best pieces of real estate on the reef, waging war on each other using their stinging tentacles.
In the case of Brazilian Mussismilia, it was found that if orange cup corals crept to within 2″ of the colonies, the Mussas would die off. The cup corals, on the other hand, didn’t appear to incur any damage from their new neighbors.
The exact effect on the local ecosystem isn’t known, but it’s not likely to be positive overall. This being said, researchers in Curaçao did notice native Christmas tree worms using Tubastraea as their hosts. That’s something, at least!
Orange cup coral facts
Diet
As mentioned, unlike many other corals, orange cup coral doesn’t contain zooxanthellae. This means it’s not able to photosynthesize: it has to catch its food itself, which it does using its yellowish tentacles.
The coral usually extends its tentacles at night. This is when its favorite food, zooplankton, tends to be active. As these little bugs drift by, they stick to the tentacles and are subsequently transported to the mouth, which is located in the middle of the polyp.
Did you know? As always in nature, it’s eat or be eaten. Tubastraea corals, including this one, are the favorite food of the golden wentletrap snail (Epidendrium billeeanum).
Planning your next snorkel trip?
Reproduction
Coral reproduction is a bit of a doozy, and this is no exception. Orange cup corals can reproduce both asexually (though budding, polyps abandoning the colony, division, and regeneration after damage, among other methods) and sexually.
The sexual reproduction of orange cup coral mostly happens through brooding. This refers to the internal fertilization and development of baby coral larvae inside the parent polyp, giving it a safer start to life than if it was just thrown into the open ocean.
Unlike many other corals, Tubastraea coccinea reproduces year-round. This certainly adds to the species’ invasive potential! Peaks in the release of larvae line up with lunar cycles, likely because these indicate when conditions are most favorable for reproduction.
If you have any more questions about the orange cup coral or if you want to share where you spotted it, don’t hesitate to leave a comment below!
Sources & further reading
Creed, J. C. (2006). Two invasive alien azooxanthellate corals, Tubastraea coccinea and Tubastraea tagusensis, dominate the native zooxanthellate Mussismilia hispida in Brazil. Coral Reefs, 25(3), 350-350.
Creed, J. C., Fenner, D., Sammarco, P., Cairns, S., Capel, K., Junqueira, A. O., … & Oigman-Pszczol, S. (2017). The invasion of the azooxanthellate coral Tubastraea (Scleractinia: Dendrophylliidae) throughout the world: history, pathways and vectors. Biological Invasions, 19, 283-305.
Fenner, D. (2001). Biogeography of three Caribbean corals (Scleractinia) and the invasion of Tubastraea coccinea into the Gulf of Mexico. Bulletin of Marine Science, 69(3), 1175-1189.
Hoeksema, B. W., Hiemstra, A. F., & Vermeij, M. J. (2019). The rise of a native sun coral species on southern Caribbean coral reefs. Ecosphere, 10(11), e02942.
López, C., Clemente, S., Moreno, S., Ocaña, O., Herrera, R., Moro, L., … & Brito, A. (2019). Invasive Tubastraea spp. and Oculina patagonica and other introduced scleractinians corals in the Santa Cruz de Tenerife (Canary Islands) harbor: Ecology and potential risks. Regional Studies in Marine Science, 29, 100713.
Mantelatto, M. C., Creed, J. C., Mourão, G. G., Migotto, A. E., & Lindner, A. (2011). Range expansion of the invasive corals Tubastraea coccinea and Tubastraea tagusensis in the Southwest Atlantic. Coral Reefs, 30, 397-397.
Riul, P., Targino, C. H., Júnior, L. A., Creed, J. C., Horta, P. A., & Costa, G. C. (2013). Invasive potential of the coral Tubastraea coccinea in the southwest Atlantic. Marine Ecology Progress Series, 480, 73-81.