New Mud Lobster on Semakau?

Update: Have dropped an email to the authors, Moh H. H. and Chong V. C., who wrote about the new species, Thalassina kelanang in RBZ. And they have confirmed that the mud lobster I found at Semakau is indeed Thalassina kelanang! Thanks to Prof. Chong Ving Ching and Moh Heng Heng for helping with the identification!

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I could still remember after I saw a mud lobster on St John's Island, I told SY that it look somewhat different from the one that I have seen on Semakau, and I was wondering if they could be of different species. But then of course, there were only 2 species of mud lobsters, Thalassina anomala and Thalassina gracilis recorded in Singapore (Update: Apologies, there are currently 5 species of mud lobsters recorded in Singapore. The sources I was reading previously was outdated. Sorry for the mistake. Thanks Robin for the update. But guess this will not affect much my comparison below.), and since both mud lobsters I found were far too big to be Thalassina gracilis, I thought I was probably wrong.

However, recently, I read on The Raffles Bulletin on Zoology that a new species of mud lobster, Thalassina kelanang, was described from Malaysia, and I started to think if this new species can also be found in Singapore. Could either one of the mud lobsters I have found be the new species?


This is the mud lobster I found on Semakau on 11 April 2009 during a Project Semakau trip.


This is the mud lobster I found on St John's Island on 12 July 2009 during a field trip.

I decided to make a comparison between the mud lobsters I found and the description in the RBZ paper.



Taking a first look, it appeared that the Semakau mud lobster (on top) does look more similar to the new species, Thalassina kelanang, especially if you look at the shape of the backend of the carapace! The St John's mud lobster looks like a Thalassina anomala. But as the former was coated with mud at many places, it's not really clear enough for me to be sure.

I decided to take a closer look at the head of both mud lobsters.



On the head of both mud lobsters, there is this inverted V ridge with some kind of divider in the middle. For the case of Thalassina kelanang, the divider extends longer than the inverted V, just like the one on the Semakau mud lobster! For Thalassina anomala, the inverted V is longer, and this can be seen on the St John's mud lobster.

Next, I decided to look at the abdominal somite.


For Thalassina kelanang, it is more of an inverted Y shape (top left diagram, and Semakau mud lobster on top right), while for Thalassina anomala, the inverted Y is not as obvious (bottom left diagram, and St John's mud lobster on bottom right). Again, this is true for both mud lobsters!


Thalassina kelanang's pereopod 1 has a row of 8 to 12 strong dorsal spines (right arrow) on the inner propodal ridge, and the lateral dorsal ridge extends to three quarters or more of the propodal length (left arrow, see the little bumps end about four-fifth of the length). These are evident in the Semakau mud lobster shown above.


For Thalassina anomala, the pereopod 1 has a row of 13-20 blunt spines or tubercles on the inner propodal ridge (right arrow), and the lateral dorsal ridge extends the entire length of the propodus (left arrow, see the little obvious bumps extends all the way compare to the earlier photo).

From the photos above, it does seem that the Semakau mud lobster could be a Thalassina kelanang! Guess I will probably need to get a specimen the next time I see a mud lobster at Semakau, so that the experts can confirm the ID.

Guess I was rather lucky. I have seen mud lobsters twice on Semakau (didn't managed to take photo the second time), once on St John's, twice at Chek Jawa (only managed to take photo of part of one of them), and another time at Pulau Tioman.


The above is the mud lobster I found on Pulau Tioman. Doesn't quite look like the previous 2 species, as it has features that are similar to or different from either species. It is much smaller than the others that I have seen, so could it be a Thalassina gracilis? Or is it something new altogether? Hmm...

Exploring Semakau with Duke University Students

This is quite a long-overdue entry actually, since we had this trip on last Friday. Haven't been feeling well over the past few days, and thus couldn't really find the energy to put up anything until today :P

Anyway, went to Semakau Landfill with Dr Dan, Dr Stan and their students from Duke University on Good Friday. Was rather happy to see Dr Dan again though I was struggling with a sore throat. It was always wonderful listening to Dr Dan as he shared his treasure trove of knowledge on the various marine organisms. I was their guide last year when they visited Sisters Island and Chek Jawa. This time round, however, I played the role of the coordinator for the trip, just to settle the boats and other logistics issues, while Ria had the pleasure of guiding him around the intertidal area of Semakau Landfill.



Here are our visitors from Duke University who just emerged from the secondary forest, getting ready to venture to the splendid shores of Semakau.



Semakau probably has the biggest seagrass meadow in Singapore. The seagrass meadow is an important nursery ground for many marine organisms, as there are lots of hiding places and food. Many of the seafood that we eat spend part of their life living among the seagrasses.



I was rather delighted to find this peacock anemone (Order Ceriantharia) among the seagrasses, since they were less common on Semakau compared with our northern shores.



Other Cnidarians we saw include the pretty anemone coral (Goniopora sp.) above and lots of other colonial hard corals. Each little flower-like structure you see above is called a polyp, and it is actually the coral animal! Colonial hard corals like this can sometimes have hundreds, if not thousands of polyps. The hard structure (or skeleton) you see is just like an "apartment" housing lots of little coral animals.



But sometimes, you get some lone rangers too, like the sunflower mushroom coral (Heliofungia actiniformis) above. All the tentacles you see above belong to one single coral animal (aka polyp). It is called a mushroom coral because the juveniles are attached to the substrate on a stalk-like structure, making it look just like a little mushroom! The coral will break away from the stalk when it matures though.



Other than the hard corals, we have plenty of soft corals at Semakau as well. Not sure about the exact ID for this one though. Unlike hard corals which have hard skeletons made of calcium carbonate, soft corals have a soft tissue connecting all the polyps.

Semakau also has no lack of sea anemones, which are relatives of the corals (from the same Phylum Cnidaria) , including some of the larger ones like the gigantic carpet anemone (Stichodactyla gigantea).



And sometimes, if we are lucky, we may even find the ocellaris clownfish (Amphiprion ocellaris) in some of them. Are indeed, we were rather lucky. The one above, probably got disturbed by the sound made by my foot steps, actually jumped on top of the anemone as I was walking past. I didn't even have to look for it!

Clownfishes and anemones share an interesting relationship. While most other fishes will be stung by the anemone's stinging cells when they touch its tentacles, the clownfish has a layer of mucus over its body that prevented the anemone from discharging its lethal stings. The fish will help the anemone by luring prey to it, increasing oxygenation, removing waste material, and protect the anemone from some butterflyfishes which feed on the anemone, while the latter helps the fish by giving it protection from predators and leftover food.



We can usually see lots of fishes at Semakau, and sometimes, that includes fishes that don't really look like a fish, such as this tigertail seahorse (Hippocampus comes). This was also the first time I saw this seahorse species at Semakau! Seahorse can usually camouflage themselves very well among the seaweeds, but guess this one's colour happened to more easily noticed :P



Another master of camouflage was this frogfish, probably a spotted-tail frogfish (Lophiocharon trisignatus). It usually slowly creeps around on its special fins (which look like paws) and catches (with its big mouth) little fishes or other small animals which didn't see it coming.

Semakau is also a wonderful place to find echinoderms, like sea stars and sea cucumbers.



Just like our other trips, we found several common sea star (Archaster typicus) before we enter the seagrass lagoon. These sea stars burrow into the sand to feed on any tiny edible organic particles.



At the rocky shore area, I was quite happy to find the cryptic rock stars (Cryptasterina sp.) again. These sea stars usually hide underneath rocks in the day away from the hot sun, and only come out to feed when it is darker. Can't remember what they feed on though. Probably algae, detritus or small clams?

Some of the others also found a few knobbly sea stars, which unfortunately I wasn't with them then to grab a few photos.

Fortunately, I managed to spot what I called the "Big Five" sea cucumbers of Semakau though.



One of the most common sea cucumbers on Semakau must be this - the sandfish (Holothuria scabra). This is usually the species that the Chinese eats during Chinese New Year, but they must be properly treated to remove the toxins before they can be consumed.



The second of the "Big Fives" - the stonefish sea cucumber (Actinopyga lecanora). We can usually find it among the rocks near the coral reef.



This is an ocellated sea cucumber (Stichopus ocellatus), which was only described in the 1990s! Sea cucumbers of this genus do not eject the sticky threads for defense, but they may eject their internal organs. When they are removed from the water for too long, they can actually "melt", become very limp and eventually disintegrate all together. However, if they are not too badly "melted", they are able to reverse this process and recover.



Also from the genus Stichopus is this dragonfish sea cucumber (Stichopus horrens). Also called the peanutfish sometimes in the sea cucumber trade, or the thorny sea cucumber or horrible sea cucumber, this fellow sure goes by many names :)



And the last, but longest, of the "Big Fives" - the synaptid sea cucumber (Family Synaptidae) .



But apart from the "Big Five", we had another surprise find - a red sea cucumber, which we thought could be an Actinopyga sp. related to the stonefish sea cucumber. First time seeing this on Semakau actually, and we found several of them among the seagrasses.

Moving on to the mollusc, and yet another interesting group with lots of fascinating animals.



Found this pretty living heart cockle (Corculum cardissa) among the seagrasses. Sadly, some people collect this shell while it is still alive, kill it and make the shells into little gifts. To me, this is certainly a heartless way to make a so-called "token of love".



Among the seagrasses, I also found this pretty noble volute (Cymbiola nobilis). These huge snails normally feed on clams and other shells. To feed, it wraps its prey in its huge foot, and waits until the exhausted clam opens up to breathe, which can take up to several days! The volute will then stick its proboscis into the shell and eats the flesh of its prey with its radula.



Also in the Phylum Mollusca, we have many beautiful little slugs called nudibranchs, and the above is one of them, a Glossodoris atromarginata. They are closely related to sea snails like the volute above, and basically, they are snails without shells. The flower-like gills exposed on its back was what gives nudibranchs their common name. Nudibranch means naked gills!



Found this cute little polka dot nudibranch (Jorunna funebris) on some seaweeds. The 2 little structures sticking out at its front end are its rhinophores, and nudibranchs use them to sniff out their prey. The polka dot nudibranchs are known to feed on blue sponges, so I was a little surprised when ST told me he saw one munching on some bryopsis seaweed! Could there be some tiny sponges growing on the seaweed? Or was it really eating the seaweed? I really have no idea...



We also saw a pair of Chromodoris lineolata getting really intimate. However, the position didn't look quite right though. Nudibranchs are hermaphrodites, meaning they have both male and female reproductive organs. They often fertilise each other when they meet in a 69 position. These two, however, are not in the standard 69 position which allows mutual fertisilation. It is known that among nudibranchs, sometimes one will assume a male role and the other a female role, so I guess it's possible that the two slugs above could just be doing that. (Update: Don't know what I was thinking when I wrote the above yesterday. The reproductive organs of the nudibranchs are always on their right side, so if they are facing the same direction side-by-side, their reproductive organs won't be able to meet, so they can't be mating here. So guess at the very most this could just be "foreplay", or they could be doing something else altogether.)



As it got darker, the slugs' distant relatives, the octopuses (Order Octopoda), also started appearing. Octopuses are known to be one of the smartest invertebrates, if not the smartest.



We also found a few cluster of squid egg capsules. While octopus and cuttlefish eggs tend to look like bunches of grapes, squid eggs tend to look like (pardon the crude comparison) bundles of inflated condoms.

Enjoying the darker and cooler surrounding were also several flatworms (Phylum Platyhelminthes).



And here's one of the commonly seen flatworms (Acanthozoon sp.). Flatworms are so flat that they can easily squeeze into small crevices to hide from predators or to seek out prey, which could be little shrimps and worms, or even sponges or ascidians.

Indeed, this Semakau trip has again been a very successful one. Hope Dr Dan, Dr Stan and the Duke University students have enjoyed themselves too.

See also:
- Pulau Semakau with Dr Dan and friends by Ria.
- Good Friday at Pulau Semakau by CH.
- Mini Cowry at Semakau by ST.
- Day 5--Semakau by Dr Stan.

Semakau Over Last Weekend

Went to Semakau over the weekend for a Project Semakau survey and also a guided walk for secondary school students. Once again, I was the coordinator for both trips. For the guided walk, NEA had only provided one bus for the trip and we had like 80 participants, and thus I had to stay with the participants to coordinate the landfill tour instead of running off to help with hunting-seeking. Fortunately, I still managed to find a few interesting stuff for the participants even though I went to the intertidal area rather late :P

Here are some of the things we saw over the weekend.


There were several Magnificent Anemones (Heteractis magnifica) near the reef edge. I did not find any anemonefish in them though.


Semakau has many species of hard corals, and the above is a Galaxy Coral (Galaxea sp.). The colony has lots of small tentacles with white tips, which resemble stars of the galaxy, and hence the name.


The Upside-down Jellyfish (Cassiopea sp.) was in season, and we saw a number of them on both trips.


Moving on to the echinoderms, we saw quite a number of Sandfish Sea Cucumbers (Holothuria scabra) despite the heat.


There were a few Dragonfish Sea Cucumbers (Stichopus horrens) too.


The Stonefish Sea Cucumber (Actinopyga lecanora) was not as numerous though. I only saw 2 of them.


Semakau has a huge population of Sand-sifting Sea Stars (Archaster typicus), that blend in really well with the surrounding sand.


It was really a day for Cushion Stars (Culcita novaeguineae). This was the smallest one we saw that day, only about 6-7cm wide.


This one was slightly bigger, about 8cm wide, I would think.


This one was regularly spotted around the same area, and it had certainly grown! The first time I saw it, it was only about 5cm wide, and now it's probably about 10cm wide.


And we also found this huge Cushion Star which we saw every now and then on Semakau. It is definitely more than 20cm wide. Some of the groups saw yet another huge one later, one which I last saw in 2008!


Semakau probably has hundreds of Knobbly Sea Stars (Protoreaster nodosus).


This was also the first time I saw this black flatworm with orange outline on Semakau. Not sure of the ID though.


There were also a number of molluscs around. The above shows the underside of a Spider Conch (Lambis lambis), which got its name from the long spines which supposedly resemble spider legs to some people.


Another pretty snail we saw was this Noble Volute (Cymbiola nobilis). This snail hunts other snails and clams to feed on.


One of the guides found this Starry Bornella (Bornella stellifer), a nudibranch which I had not seen on Semakau for a few years!


Even more colourful was this Varicose Phyllid Nudibranch (Phyllidia varicosa). This slug can secrete a whitish toxic substance into the surrounding water when it's stressed. Was rather excited to find this since I had not seen it for quite a while.


I also found some nudibranch egg ribbons among the seagrass.


Our good old resident Fluted Giant Clam (Tridacna squamosa) was still at the same old spot.


I found this bivalve during the survey - my first time seeing it on Semakau. Have not checked with SK what it is, though it sure looked like some kind of mussel. Update: Have checked and it is a Brown Mussel (Modiolus philippinarum).


Another nice find of the day were a pair of Tigertail Seahorse (Hippocampus comes). The above is a female.


And this is the male Tigertail Seahorse. Looks like it's pregnant. Male seahorses have a brood pouch, which the females will deposit their eggs inside, and the former will then fertilise and protect the eggs until they hatch.

It was certainly 2 very hot days on Semakau, but certainly 2 very fulfilling days for me with many great sightings! :)