Lobsters at St John's

Today is Lobster Day at St John's Island!


First, we saw the moult of a Mud Spiny Lobster (Panulirus polyphagus). Ok, we did not see a living specimen, but I am satisfied seeing the moult. You need to have a living lobster to shed the moult, right? That shows that we still have wild lobsters in our waters! This lobster is usually found on muddy bottoms, though sometimes it can also be found on rocky substrates. The last time I saw any wild lobsters in Singapore was in the year 2006, when we saw 2 different species of lobsters, also on St John's Island.


This was one of the lobsters which I saw in 2006 - a Painted Spiny Lobster (Panulirus versicolor). The other was a smaller Mud Spiny Lobster which I forgot to take photos. And these were real living lobsters, not just the moult. The Painted Spiny Lobster is said to be found in shallow water in coral reef areas, and is nocturnal.


It appeared that our "lobster luck" today did not end with the Mud Spiny Lobster, as we also found a Mud Lobster (Thalassina anomala) near the mangroves! It appeared that it was lucky for the Mud Lobster that we spotted it too, as it was trapped stuck to a piece of discarded thread, which was in turn entangled around the stem of a Mile-a-minute creeper (Mikania micrantha).


I quickly took out my Swiss knife to cut away the thread to release the Mud Lobster, not an easy task though as it was struggling and I was worried that I might accidentally hurt the animals. Fortunately, nothing went wrong and I managed to release it.

Anyway, I was back on St John's Island today to conduct a training for some new guides. And of course, apart from the lobsters, we saw quite a number of other interesting animals too, and here are some of those which I remembered to take photos of.


This may look like a lobster, but it is not. It is a Snapping Shrimp (Family Alpheidae, Order Caridea). The Food and Agricultural Organization of the United Nations classifies crustaceans from the infraorders Astacidea, Palinuridea and Thalassinidea to be marine lobsters. Nonetheless, the Snapping Shrimp is a very interesting animal with one enlarged claw which can make a very loud "pop" sound to stunt fishes. It is said that the pressure released when the shrimp snaps its claw can even kill small fishes!


Another crustacean we saw was this black hermit crab with gold spots. I have no idea what species this is though. Hermit crabs have a soft abdomen which they need to hide in an empty shell so as to protect it from predators. As they grow bigger, they will have to change to a larger shell! (Update: This is Clibanarius cruentatus. Thanks to Yoyo for the ID!)


On the other hand, true crabs like this female Fiddler Crab (Uca vocans), are covered all over with a hard exoskeleton to protect them from various predators.

While female Fiddler Crabs have two equal-sized claws, the males have one enlarged claw. The enlarged claw cannot be used for feeding, as it is too big to pick up sand, and this crab feeds on tiny organic particles among the sand. It is used mainly to attract females and to fend off competing males. The bigger the claw, the more attractive the male is to the females, as that shows that the male has good genes and the resources to survive despite this huge and cumbersome claw. The females, with two equal-sized claws, can thus eat double-quick, and this is also important as they need to lay eggs and require more nutrition.


Some of the new guides spotted this Spiral Melongena (Pugilina cochlidium) burrowing away. Near the snail were some egg capsules. Not sure if they belong to this particular snail, but they (the whitish stuff on top right) are indeed Spiral Melongena eggs.


Often mistaken by beach-goers to be a centipede, this animals is actually a segmented worm commonly called a Bristle Worm. Unlike the centipede, which is an arthropod, the Bristle Worm does not have legs, but instead have bristle-like structures to help it moves.


We also saw a Fireband Murex (Chicoreus torrefactus). This murex is often collected for food and shellcraft in the region.


Near the coral reef area, we also saw a Black Long-spined Sea Urchin (Diadema setosum). This sea urchin feeds on algae, and helps keep the algal population in check in the coral reef.


It's been a while since I last saw a Striped Ribbon Worm (Baseodiscus quinquelineatus) at St John's Island. Many of these long, soft and ribbon-like animals are poisonous to be eaten, and some can even give venomous stings.


One of the most commonly seen nudibranch in local waters must be this Funeral Nudibranch (Jorunna funebris). The name nudibranch means "naked gills", refering to the flower-like gills on the back of most species.


An intertidal walk never feels complete with a star-sighting. There are many Sand-sifting Sea Stars (Archaster typicus) on the sandy shore. This sea star can burrow into the sand to hide from predators and also to seek for tiny food particles among the sand which it feeds on. This sea star is one of the most common ones in Singapore, and can be found on most of the islands that I have visited.


After the intertidal walk, we went to take a quick look at the mangrove and coastal forest. The Mangrove Cannonball (Xylocarpus granatum) was fruiting and we saw many of them. It got its common name from the big and round fruit.


Several Cotton Stainer Bugs (Dysdercus decussatus) were found on a Sea Hibiscus (Talipariti tiliaceum). These bugs feed on the seeds of the latter.


While we were heading back to the jetty, I stopped by one of our native Pong Pong Tree (Cerbera manghas) at the edge of the coastal forest. Unlike the ones we usually see on our roadsides which flowers have a yellow centre, our native Pong Pong flowers are coloured pink in the centre.

It was certainly nice to see so many of our native trees being planted here!

Going back to the main topic of the day on lobsters, so far I have only seen wild spiny lobsters on St John's Island, though I understand that my other friends have seen it while diving else where in Singapore. Sure hope that one of these days, I can see them on other islands during intertidal walks!