Mushroom Coral

Domain: Eukarya
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Order: Scleractinia
Family: Fungiidae
Genus: Fungia
Species: Fungia scruposa

Do you know what gets my attention? An old article about a species of coral that was documented eating jellyfish. But I’ll get to that later; first, I want to introduce you to Fungia scruposa, or the mushroom coral!

Found in the tropical waters of the Red Sea, Indian Ocean, and western Pacific Ocean, mushroom coral are unique for a few reasons. Unlike other hard corals, F. scruposa lives as a single individual instead of as a colony, much like the Atlantic mushroom coral of the family Mussidae. Don’t let their similar common names fool you, though. These two corals are not closely related to each other.

Juvenile mushroom coral start out as raised disks that attach to dead coral or rock. When they grow to about an inch in diameter, they detach themselves from their substrate. However, this does not mean that they’re super mobile. Instead, mushroom coral typically stay in the same area and inhabit the sediment or rubble.

But what happens if a strong wave comes through and turns them over? Fungia scruposa use their tentacles to right themselves when knocked over by waves or by another animal.

Mushroom coral get their name from their appearance. They have an irregular disk shape that is about 1 inch in diameter, sometimes a little larger. At the center of the disk is a raised mound with a deep-looking cut, which is the polyp’s mouth. The coral’s hard exoskeleton has several thin ridges that spread out from the center, making it look like the underside of some mushrooms.

Fun fact: did you know that the ridges on the undersides of mushrooms are called gills?

I’ve yet to see this coral while diving, but I absolutely cannot wait! Mushroom coral are unique for their class, because they live as solitary polyps and spend their adult lives not attached to anything. But on top of all that, they were also recorded eating whole jellyfish in the late 2000s—something that was completely unheard of!

There are some species of sea anemones—distant cousins to coral—that are known to eat jellyfish. However, these are the first hard corals that scientists have seen eating jellies. Unfortunately, the divers were only able to see the jellies disappear into the mouths of several mushroom coral, but they could never see how the mushroom coral captured the moon jellies. Still, it’s absolutely fascinating and may prove how resilient hard coral can be in a changing ocean environment.

And maybe you can be the researcher that discovers how they do it! Maybe you can discover more species of coral that will dine on jellyfish when the opportunity presents itself.

Sources and links:
Ocean The Definitive Visual Guide made by American Museum of Natural History
http://www.coralsoftheworld.org/species_factsheets/species_factsheet_summary/fungia-scruposa/
http://news.bbc.co.uk/earth/hi/earth_news/newsid_8350000/8350972.stm ⇐an article about mushroom coral eating jellies
https://link.springer.com/article/10.1007/s00338-009-0507-7 ⇐another article about them eating jellies but with more detail

Atlantic Mushroom Coral

Domain: Eukarya
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Order: Scleractinia
Family: Mussidae
Genus: Scolymia
Species: Scolymia lacera

Not all hard coral grow to be great big structures. And while most coral are considered to be a colony of polyps—i.e., individuals living together—there are some that are quite solitary. Some of them, like the cup corals, live a bit differently than their cousins and distant relatives.

Atlantic Mushroom coral, or Scolymia lacera, is one of a few cup corals found in the Western Atlantic Ocean. In fact, they occasionally can be found in deep-reef environments and on reef walls in the waters around Florida, the Bahamas, and the Caribbean. They prefer well-lit areas on rocky surfaces and outcroppings, somewhere nice and stable with enough light to help out their zooxanthellae friends.

S. lacera varies in color from shades of light gray to green, blue-green, and brown. The few that I have seen while diving were a mix of blues and greens, almost like an alternating stripped pattern—though this isn’t the same of all individuals.

Unlike other coral, the whole structure that is S. lacera is made up of a single polyp. That’s right; this species of coral is not a colony like its other hard coral cousins. Instead, it is a single large, fleshy, roundish polyp that looks a bit rough around the edges—texture-wise, that is. The whole structure that you see is the corallite, or the skeletal cup in which an individual polyp sits in and can retract into. For S. lacera, the center of the corallite can be either flat or curved inward; rarely is it seen with a raised center.

The Atlantic Mushroom coral can grow to between 2.5 and 6 inches and is the only type of cup coral that you can identify in person if it’s larger than 4 inches in diameter. Any specimen smaller than 4 inches has to have its corallite structure examined for identification.

During the night and in turbid, cloudy conditions, the polys will extend their tentacles in the hopes of grabbing food.

I think these guys are really cool because they break the mold, so to speak, when it comes to most hard corals. Instead of being a colony of individuals, each structure is a single large individual. They’re also pretty neat to spot on the reefs because they can be these bright colorful spots amongst drab shades. When I first saw them I didn’t think they were coral. It wasn’t until I started taking classes and we discussed them that I learned what they were.

Sources:
Reef Coral Identification: Florida, Caribbean, Bahamas 3rd edition Paul Humann and Ned DeLoach

https://coralpedia.bio.warwick.ac.uk/en/corals/scolymia_lacera <–At the time of posting this article, I hadn’t gotten the rights to share any photos of the coral, but you can see pictures of this species at the link–please take a look!

Giant/Boulder Brain Coral

A boulder brain coral (Colpophyllia natans) growing on a coral reef. Photo taken by D. Alex Mustard, more can be found at www.amustard.com

Domain: Eukarya
Kingdom: Animalia
Phylum: Cnidarian
Class: Anthozoa
Order: Scleractinia
Family: Mussidae
Genus: Colpophyllia
Species: C. natans

First let me state that I have a love/hate relationship with common names. Most people call the Colpophyllia natans the Boulder Brain Coral; however, there are some texts and articles that call it the Giant Brain Coral. Why is this frustrating and worth mentioning? I spent a good chunk of time trying to confirm that these guys are the same species with different common names—I really didn’t want to make a fool of myself!

C. natans are named Boulder Brain Coral because they typically form large rounded structures that look like, drum roll please, boulders. They can also form large rounded plate-like structures, encrusting over rocks and existing coral colonies.

Like other brain coral, C. natans look like someone gave a chisel to a child and told them to go wild on the coral, creating a random pattern of valleys and ridges on the surface. A thin groove runs along the very top of the ridges, though you usually can’t see it when diving because you’re too far away (and if you’re not, you should be).

A second line is found halfway down the ridge where the angle decreases and slopes to create the valleys. The valleys are usually long and wandering, almost path-like, but sometimes they’re closed up and look more like individual cells squished together. The coral polyps are found within the valleys; the long ones containing multiple individuals, while the closed ones hold one or two polyps.

The ridges and valleys are normally different colors from each other. Ridges are either brown or gray while the valleys can be green, tan, or whitish.

You can commonly find them on reef tops or seaward reef slopes in the tropical waters of the Gulf of Mexico and the Caribbean. They can grow to have a diameter of up to 16 feet and can live as long as 100 years! C. natans are extremely popular tourist attractions, especially in the Florida Keys. But divers aren’t the only things these guys attract; they also attract all kinds of fish, including some gobies that live permanently on the coral.

I’ve only ever seen these guys during day dives—which, trust me, is still really cool to find them because of their size and coloring. However, they’re even better to see on a night dive because that’s when the polyps let out their tentacles to fish for zooplankton. I’ve been told that the coral can look completely different at night, and I can’t wait to see it for myself in person!

Sources and cool links:
Coral Reef Identification: Florida, Caribbean, Bahamas 3rd Edition by Paul Humann and Ned DeLoach
Ocean The Definitive Visual Guide made by the American Museum of Natural History
http://species-identification.org/species.php?species_group=caribbean_diving_guide&menuentry=soorten&id=305&tab=beschrijving
http://www.coralsoftheworld.org/species_factsheets/species_factsheet_summary/colpophyllia-natans/
https://www.sealifebase.ca/summary/Colpophyllia-natans.html
http://www.wildernessclassroom.com/wilderness-library/giant-brain-coral/

Elkhorn Coral

Image was taken by Dr. Alexander Mustard, who has given me permission to use his photos on this blog. You can look at his gallery here: http://www.amustard.com/

Domain: Eukaryota

Kingdom: Animalia

Phylum: Cnidaria

Class: Anthozoa

Subclass: Hexacorallia

Order: Scleractinia

Family: Acroporidae

Genius: Acropora

Species: palmata

So the first species I decided to tackle was a coral; gee, what a surprise. For those of you who don’t know, coral and their reefs are what held my interest in the ocean after my dolphin phase ended.

Acropora palmata, or the Elkhorn coral, is a species of branching coral that can be found in the Caribbean. This was one of the corals I had to learn to identify for an independent study and class my last semester of college, and one that I became very familiar with during an experiment I planned and executed. Elkhorn coral are also one of my favorite corals to find while swimming in their waters. Typically it appears brown to brownish-yellow in color and it has wide flattened branches that resemble…drum roll…elk or moose antlers. It looks very similar to one of its’ cousins in the same genius, Acropora cervicornis (Staghorn Coral), but its’ cousin has thin cylindrical branches that look like the rack of a buck.

In shallow, unprotected waters Elkhorn branches will grow to be rounder and stouter, like fat fingers, to help protect the coral against violent waves and storm surge by decreasing their surface area. Colonies found in more moderate depths, where wave action has less of an impact on the structure, have long, wide, and flattened branches like the leaves of palm trees.

Have you ever stuck your hand out the window in a moving vehicle? If not, you should try it next time, but please be careful—impacts from high-speed bugs hurt! When you stick your hand out the window with your fingers splayed out like a turkey, you feel less resistance from the wind because it has space to move around your fingers. When your fingers are close enough that they’re touching, you feel more resistance from the wind because now it has to move around your hand because there’s not enough space between your fingers.

The same happens with Elkhorn coral in high energy water, meaning lots of intense waves, they produce thick round branches to allow enough space for the water to flow through and reducing any potential damage to their structure. Outlining the Elkhorn branches are white terminal corallites, which are hard cups made of calcium carbonate secreted by the coral. A corallite is like the home of an individual polyp, it is a hard structure that houses the polyp and allows the individual a place to hide and retract itself when it’s not gathering food.

The Elkhorn coral was once abundant in the Florida Keys, but are now more scarce and scattered in the area. In the Bahamas and the Caribbean they are considered to be common, since they can be frequently found, but not at every dive site or reef. Divers saw a lot more of these coral before the 1990s, but since then they have suffered high mortality rates due to storms, bleaching, and most commonly by White-band Disease, a disease that I will discuss more later−just know that it is a disease that affects species of coral.

One of the cooler things that I learned about this coral is that you can determine the direction of the surge, or the typical movement of water, by the direction the branches grow. Elkhorn branches grow parallel to the direction the surge takes, much like some trees grow in the direction of the prevailing wind on land.

Elkhorn coral can be found between 1−35 feet of depth, and they prefer areas of constant water movement caused by incoming waves. They can grow rapidly under optimum conditions, growing up to five to six inches a year. Because of their rapid growth for reef builders, the family Acroporidae is commonly used in reef restoration and growth programs. They make for a good starting block for man-made or rehabilitated reefs.

If you see this coral while diving or snorkeling, please do not touch it, and try to keep your equipment from getting caught in it. While not extremely fragile, it can still break under pressure. So please be careful while you swim and enjoy the view from a far; reefs are very important not only to the ocean but to us as well!

Source: Humann P, DeLoach N. 2013. Reef coral identification: Florida, Caribbean, Bahamas. 3rd ed. Jacksonville, Florida: New World Publications.