I had been looking forward to this trip, as I was sure that we would have quite a few good finds. And true enough, despite the heavy storm the day before, we had several interesting sightings!
The top find of the day for me must be this Mud Lobster (Thalassina anomala)! This was my first time seeing the entire animal in Singapore. The previous 2 times that I saw an entire mud lobster was on Pulau Tioman, while the only other time I saw part of a Mud Lobster was at Chek Jawa. This secretive animal usually hides in the mud mound it built (called Mud Lobster Mound), but sometimes it will emerge at night, especially when it rained earlier. Mud Lobsters are very important in a mangrove ecosystem. They feed on organic particles found in the mud, and as they eat and dig into the mud, the mud from underneath got piled up on the surface, forming a little mound.
Many other plants and animals live in or on Mud Lobster Mounds too, attracted by the nutrients brought up to the surface with the mud, and also, higher ground and free lodging (burrow made by the Mud Lobster) to get away from the sea water.
Another interesting find for me was this Dog-faced Water Snake (Cerberus rynchops). This was the second time I saw this snake on Semakau, but I did not take any photos the previous time. This snake is mildly venomous and feed on small fishes. It sometimes hunt other small animals too.
And finally, we found a Banded File Snake (Acrochordus granulatus) that was not covered with algae! This non-venomous snake feeds mostly on small fishes.
I came across this interesting snail on the sandy shore. Looks like a Strombus vittatus to me, but guess I have to double-check with SK to be sure.
Part of a dead Heart Urchin was found at the reef crest. I have not seen this type of heart urchin on Semakau before. When will I find a living one?
One animal which really got us puzzled. It looked like a slug, but while examining it closely, I noticed that it had an internal shell that appeared bivalved, with the hinge on top, and the opening below. Guess we will have to check with our malacologists again to find out more.
This one is definitely a slug though, a Funeral Nudibranch (Jorunna funebris), which got its common name from its black-and-white coloration.
Another nice find was this Copper-banded Butterflyfish (Chelmon rostratus). It has a large 'false eye' on its dorsal fin, while the real eyes are concealed by a vertical band. If a predator attacks it, it will attack the 'false eye' at the back, and the butterflyfish can quickly swim forward to avoid the bite. The big 'false eye' also tricks predator into thinking that the fish is bigger than it really is.
Semakau is a nice place to spot these beautiful Red Maiden's Fan Sponges (Oceanapia sagittaria).
This mud ball is also a sponge (Cinachyrella australiensis)!
Living on the seagrass are various types of Colonial Ascidian. Sometimes mistaken to be sponges, they can usually be differentiated from the latter by the numerous little spots found on them, usually of a different coloration, which are actually the individual ascidian animals.
Giant Carpet Anemones (Stichodactyla gigantea) are very common on Semakau, and many of them have anemonefishes or shrimps living with them.
I saw this pretty Tube Anemone (could be a Cerianthus sp.) near the reef edge.
This cute little Upsidedown Jellyfish (Cassiopea sp.) was found in a little tidal pool at the sandy shore. I later found another three of them. This jellyfish has symbiotic algae in it, which photosynthesizes better with it being upside-down. Some of the food made by the algae will be shared with the jellyfish.
The sand bank also has lots of Sand Dollars (Arachnoides placenta)!
Some of the volunteers found this Crown Sea Star (Asterina coronata). This small sea star can usually be found among the seagrasses here.
We soon completed the survey, and on my way back to the meeting point, I came across 4 Knobbly Sea Stars (Protoreaster nodosus). Here's one of them. Heard from the other volunteers that they saw many of them today.
Well, our first hunting-seeking survey certainly had several great findings. Can't wait to see the reports from the other groups if they have found other interesting stuff!
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