Zoanthids of Cyrene Reefs

At a very civilised hour of 7am, we're off to Cyrene Reef with Dr James to look at zoanthids.

On the way out, Yi xiong spotted two dolphins! But there rest of us were asleep or not paying attention and missed them :-(Here are the intrepid explorers making the amphibious landing.Dr James is really cool and fun to have on our trips!

As soon as they arrive, they find a special zoanthid that Dr James first saw at the Galapagos!I don't have photos of the zoanthid because I was then still on the big boat :-( But I'm sure someone on the team will blog about it soon.

By now, we are a little better at zoanthid ID.

Zoanthus species are smooth as they don't incorporate sand in their bodies.Zoanthus vietnamensis usually (but not always) has a pink centre when it's closed and is larger than Zoanthus sansibaricus. When opened, the oral disk can be green or other colours.Here's another patch of probably Zoanthus vietnamensis.And yet another patch of probably Zoanthus vietnamensis.

Zonathus sansibaricus tends to be smaller and have relatively longer tentacles.Palythoa mutuki has a much larger oral disk and relatively short tentacles. It incorporates sand into its body so it feels rough to the touch. But be careful and don't put your finger into your mouth or your eye after touching it as these may contain toxins.This is a typical Palythoa mutuki.But Palythoa mutuki can also have a plain oral disk as well as other patterns.

To make matters more complicated, the various zoanthids are often found crammed next to one another. Here are some possible IDs of various combinations of these zoanthids.Green Zoanthus vietnamensis on the left and brown Palythoa mutuki on the right.Big brown Palythoa mutuki among smaller Zoanthus vietnamensis.
Smaller light brown Palythoa mutuki and bigger dark coloured Playthoa mutuki among paler Zoanthus vietnamensis.
Big brown Palythoa mutuki among much smaller Zoanthus sansibaricus both carpeting the ground under seagrasses at Cyrene.

Many intertidal zoanthids also contain symbiotic algae (zooxanthallae) that undergo photosynthensis. So they also need sunlight. In the seagrass meadow, they are kind of like the understorey of the mini-forest. Dr James says there might be so many zoanthids on Cyrene Reef's seagrass meadows because the water there is clear, thus allowing sunlight to reach the zoanthids even under the seagrasses.

For animals that need to cling to a hard surface and get sunlight, real estate has a high premium.So zoanthids crowd next to one another and with sponges and other encrusting animals on the rocks and rubble of Cyrene.Here's a carpet of two kinds of zoanthids (on the left) crowding next to a brown sponge on the right. It's a slow and silent constant battle for territory on the shores of Cyrene.

Some other animals are sometimes also mistaken for zoanthids.The pink animals on the right are the big polyps of a hard coral, Turbinaria sp. While the brown Zoanthus mutuki is on the left.

Sometimes confused for zoanthids, are corallimorphs.Corallimorphs are solitary polyps, although they are often found in groups and may sometimes carpet large areas of coral rubble. Most corallimorphs don't have long tentacles and instead have bumps or other small projections on their large oral disk. Corallimorphs are distinguished by an upturned mouth in the centre of the oral disk.

The Anemone coral (Goniopora sp.), a hard coral, also has large long tentacles that are sometimes mistaken for zoanthids.Another animal that is often confused for zoanthids are these fluffy ones.Dr James says they are Briareum species, a kind of soft coral. Wonderful! I've always wanted to know what they were.

We saw lots of other interesting marine life on Cyrene as well. I'm sure the others will blog about these soon.

For me the most intriguing encounter was with this Cake sea star look-alike.When we first saw it (photo on the left) it certainly resembled a Cake sea star (Anthenea aspera). When we looked at the underside, it became obvious that it was a Cushion star (Culcita novaeguinea).We put it in water and it looked a little more like a Cushion star, although it was really flat for one. We think it might be a juvenile Cushion star.

Alas, throughout the trip, there was a small boat laying large fish traps around the perimeter of Cyrene Reef.The fish traps are really huge!
Otherwise, today was a really pleasant day out.The ominous phalanx of marching clouds earlier seen when we started the trip loomed over us all morning, heavy with moisture. But there wasn't even a sprinkle and they kept the day cool and pleasant.As usual, we squeak back just before the incoming tide. All thanks to Melvin who valiantly brought us to Cyrene despite having other business to attend to at the same time. (We also secretly think it's Melvin who gives us the good weather).A final photo of Dr James, the coolest zoanthid guy, with the lovely Liana, before we head of to replenish on prata of various subspecies.