Bubble Coral Plus

by B. N. Sullivan

Plerogyra Sp. with Waminoa flatwormsIn the previous article, we introduced our readers to Bubble Coral (Plerogyra sinuosa), a type of stony coral recognizable by the inflated bubble-like vesicles that give rise to its common name. Sometimes other little creatures live in or on the Bubble Coral. We refer to that situation as Bubble Coral Plus.

For Wordless Wednesday, we posted a macro photo of Bubble Coral with a tiny shrimp (Vir phillipinensis) that makes its home among the Bubble Coral's vesicles. The first photo on this page shows another instance of Bubble Coral Plus. This time the Bubble Coral is host to an entirely different critter, the Waminoa flatworm.

The first time we saw Waminoa on Bubble Coral we thought it looked like some kind of algae growing on the surface of the vesicles. We found out only recently that the spots actually were tiny critters. Apparently not too much is known about these flatworms, except that they inhabit some soft corals, as well as the soft parts of the Bubble Coral, and once they are established, the reproduce rather quickly.

Plerogyra Sp. with Waminoa flatwormsThis second photo is a 1:1 macro shot. If you click on the photo to enlarge it, you'll be able to see that the Waminoa flatworms look like little pancakes clinging to the surface of the Bubble Coral vesicles. Apparently not a whole lot is known about the Waminoa flatworms, but it is thought that they in turn are host to tiny dinoflagellates -- single cell life forms that produce nutrients through photosynthesis, some of which they share with their host.

I took both of the photos on this page in the Celebes Sea at Bunaken Island. The little island is part of an offshore marine reserve near Manado, on the northern finger of Sulawesi Island in Indonesia. Most of the Bubble Coral in this area has a golden or greenish tinge to it, whereas most of the Bubble Coral we saw in the Red Sea was white, sometimes with a pale bluish tinge. We are not certain if the Bubble Coral in the Celebes Sea is the same species as that in the Red Sea, but it belongs to the same genus, Plerogyra.

Someone who commented on the Wordless Wednesday photo of Bubble Coral mentioned that she had been snorkeling for a long time, and had visited many places, but had never seen Bubble Coral. That was not surprising to us, since it is not usually found at snorkeling depths. We have seen Bubble Coral at many dive sites in the Red Sea, and in various places in the waters around Indonesia and Malaysia, but never at depths of less than about 15 meters (50 feet). Thus, it is unlikely that snorkelers would get to see it.

Bubble Coral

by B. N. Sullivan

Bubble coral on a Red Sea reefWe have displayed a lot of photographs of reef scenes on The Right Blue. Reefs are formed by corals. The stony corals in the order Scleractinia are the reef-building corals that secrete calcareous skeletons for their polyps, which accumulate over time to become the hard framework of reefs.

We have posted quite a few photos of different kinds of soft corals, ranging from 'broccoli coral' and other Nephtheids to sea fans. Soft corals generally are more colorful and showy, and so they often are more attractive subjects for photography, but without hard corals, there would be no coral reefs. Until now, we haven't really focused much on stony corals, so we thought it was time we introduced some of the more interesting ones to readers of The Right Blue.

Some hard coral colonies form massive lumpy structures that look much like rock. Other stony corals form into fingers, pillars, antler-like branches, or even structures that look like plates. The ridged ones commonly referred to as 'brain coral' belong to the stony coral group, too.

Bubble coral vesiclesOne of the more unusual-looking stony corals we know about is Bubble Coral, an organism in the family Caryophyliidae. The first photo on this page shows a large colony of Bubble Coral on a reef in the Red Sea. If you click on the photo to enlarge it, you will see clusters of what look like bubbles -- thus the common name. Those bubbles, or 'vesicles' as they are properly called, are little balloon-like structures with rubbery skin that inflate during the day.

At left is a macro photo of the vesicles. The species in these photos, Plerogyra sinuosa, is quite common in the Red Sea. Usually it is found on steep slopes or on the vertical walls of underwater cliffs at depths of about 15 meters (50 feet) to about 40 meters (130 feet). I shot the first two photos on this page at Ras Mohammed, a well-known reef at the tip of the Sinai Peninsula.

I took the third photo on this page during a night dive off the coast of Tiran Island, which is situated at the mouth of the Gulf of Aqaba. Although we are not 100% certain, we believe that the organism in the photo is Bubble Coral of the same species as the photos above. Unfortunately, we did not get to return to the same spot in daylight to verify that this was indeed Plerogyra sinuosa.

Plerogyra at nightAt night, Bubble Coral looks very different than it does during daylight hours. The Bubble Coral's vesicles deflate, exposing its tentacles and its mouth.

In the photo at right you can see what appear to be the partially deflated vesicles, as well as the little tentacles. The tentacles can sting.

By the way, the vesicles of this species usually are whitish, often with striations of grey or very pale blue. They are translucent, and can look slightly opalescent. We have seen Bubble Coral elsewhere with a golden or greenish tinge. Next time we'll show you some more Bubble Coral, this time from Indonesia. The Bubble Coral we saw there had some 'extras' that led us to think of it as Bubble Coral Plus.

A theme song for The Right Blue

Our blogger friend LavenderBay came up with cool idea the other day, which she wrote about on her blog, Voice of the Turtle. She said:
I was reflecting this morning that I already hear a particular pop song in my head for two of your real-life blogs. So I thought, wouldn’t it be fun to play around on YouTube and discover other theme songs?

I had three criteria: I really like the song; it has to come from the country where the blogger lives; and it can be located on YouTube.
In her article, A Musical Interlude, she then listed a dozen blogs from her blogroll, chose a song that she associates with each blog's content, and posted links to the YouTube video for each of those. We think this is a clever and appealing concept. Go and have a look, and you'll see what we mean.

For The Right Blue, she chose John Denver's song "Calypso," about Jacques Cousteau's ship and undersea adventures. We are truly touched and honored by her choice, and we thank her. Here's the music video:

(If the video does not play or display properly above, click here to view it on YouTube.)