Intertidal Life of Pulau Tioman

I was really looking forward to explore the intertidal area on Pulau Tioman wiht the PJC students, especially after reading Siyang's blog about his field study. On this particular day, the tide was supposed to be the lowest around midnight, but we figured it should be low enough for a walk around 9 plus.

I was tasked to lead Group 2, which comprised only gals. Had some bad experience with shrieking school gals at my other guided walks before, but luckily this group was not too bad. A bit of screaming here and there when we spotted interesting things, but at least I wasn't exactly deafened after the walk :)

Some of the PJC students asked me why we do not conduct the walks in the daytime, as it was very difficult to see things in the dark. Well, if they had been observing their surroundings when they were playing beach volley, they would probably have realised that the tide was too high during the day to conduct the walk :P

Anyway, here are some of the interesting things we saw during the walk, organised according to the Phylum. Unless otherwise stated, most of the animals mentioned below can also found on Singapore shores!

Phylum Arthropoda



One of the first few animals we encountered was this marine spider (Desis sp.). This spider can't breathe in water, and thus it has to hide in air pockets among rocks during high tide. When the tide is low, it will come out to hunt for small animals with its venomous fangs which paralyses its prey.



We also saw lots of crabs, including the red-eyed reef crab (Eriphia smithi) on top left and the brown egg crab (Atergatis floridus) on the right. The former is a very aggressive and fast-moving crab with powerful pincers. One of the pincers is slightly enlarged with teeth to crush shells, which it feeds on. The latter is a poisonous crab. If eaten, the crab's toxins can sometimes kill a person.



This is a crab I spotted near the reef which I have no idea what species it is. Have never seen this before. Perhaps Ngan Kee or someone can help to ID?

Other crabs we spotted include velcro crabs, swimming crabs, sand bubbler crabs etc which I didn't took any photos of them. There were also lots of little shrimps hiding between rocks and seaweeds too.

Phylum Chordata



There were at least few gobies (Family Gobiidae) in every tidal pool. Gobies are bottom-dwellers, and thus they have their eyes on top of their head to have a good view of the surrounding, keeping a lookout for predators.



We also found this pufferfish (Family Tetraodontidae), which was probably very much disturb by us crowding around it that it got itself all bloated. Imagine a predator suddenly found the pufferfish bloated up llike a ball, it would probably pause for a while, giving the pufferfish the opportunity to escape to safety. The skin and certain internal organs of many pufferfish are highly toxic to humans, but still the meat of some species is considered a delicacy in both Japan and Korea.



The pufferfish's relative, the porcupinefish (Family Diodontidae), also decided to show up! Unlike the puffers, the porcupinefish has spines on its body, and so when it inflates itself, it will become a ball of sharp spines!

Phylum Cnidaria



Some how, there were not many sea anemones (Order Actiniaria) in the intertidal area. sea anemones are related to corals and jellyfish. An anemone has stinging cells in its tentacles that can paralyse animals that got too close to it. The animal will then be moved to its mouth in the centre using the tentacles. Not exactly sure about the ID of the above 2 anemones, but I think the one of the left is probably an Anthopleura sp., while the other is a Phymanthus sp. Did not see any of the big anemones found on Singapore shores, like Stichodactyla, Heteractis or Macrodactyla, and thus, also did not see any nemos. Not quite sure why the big anemones can't be found here. Is the habitat not right for them? Or have all of them been collected?



Frankly, the number of species of corals we saw at Tioman was certainly not as many as the ones we would see in Singapore, but the sizes of the colonies were simply amazing. The entire reef seems to be dominated by Acropora though.



This is probably another species of Acropora. These corals are basically colonial animals. Every coral colony contains hundreds or even thousands of little holes, and each little hole has a little coral animal (aka polyp) living inside. The coral structure was made mainly of calcium carbonate. Doesn't that remind you of us living in HDB flats?



Most of our corals get their colour from symbiotic algae called zooxanthallae, which like the ones in the giant clam, provide food for the corals. The above is yet another species of coral which I'm not sure of the ID.



Compared with the hard corals, there were much few soft corals. You can see the dead men's finger soft corals (Sinularia sp.) lying between the boulder corals (probably Favia sp.). Unlike the mushroom corals which are hard corals, soft corals don't have hard skeletons, but instead, the polyps are connected by a soft tissue mass.

Phylum Echinodermata



I've always like sea stars, and so I was really happy to find the rocky areas covered with lots of little sea stars (probably Cryptasterina sp.)(top-left). Understand that they can be found on Semakau Landfill in Singapore as well, though I haven't seen them myself. A while later, we found another species of sea star (top right) which I have not seen before and couldn't identify.

A sea star uses sea water instead of blood to support its body and to move around on its little tube feet underneath, so don’t take them out of water too long, as it is very stressful for them. Sea stars are also able to regenerate broken arms, provided that the central disc is not damaged.
Both the sea stars above were quite small, with the no wider than 3cm, and the unidentified sea star about 5cm. I was really hoping to find some bigger ones, like the knobbly sea stars or cushion stars.



But instead, I found 2 of the above sea stars among the coral rubble! I've never seen this sea star before as well! It was slightly bigger than a sand sifting sea star (Archaster typicus) , but its arms were fatter. Suspect it's probably an Asteropsis carinifera. Being a star lover, this was certainly my highlight of the day!



The number of sea cucumbers there was also quite impressive. From top-left clockwise, we have the lollyfish sea cucumber (Holothuria atra), an unknown sea cucumber which can also be found on our southern islands, a peanutfish sea cucumber (Stichopus horrens) and a tiger tail sea cucumber (Holothuria hilla).



And another animal that got me really excited initially was this pretty pinkfish sea cucumber (Holothuria edulis) which I was seeing for the first time, until they started appearing like every where. Like the sea stars, sea cucumbers are made of a tissue which allows them to keep their body soft when they are moving around, but yet in an instance, they can turn rock hard to protect themselves when they feel threatened. And by the way, do you know that a sea cucumber actually breathes through its anus?



This is probably a greenfish sea cucumber (Stichopus chloronotus) - yet another first time for me. Don't understand why the common name is greenfish when it's all black.



There were also several long-spine sea urchin (Diadema setosum). These sea urchins have long, sharp and brittle spines which break easily, so don't handle with bare hands! They normally graze on algae and also scavenge.



Here's another sea urchin which has shorter spines that I don't know the ID. There were lots of them in the deeper pools.



I also found a lonely feather star (Class Crinoidea). A feather star has a mouth on the top surface surrounded by "feathery" arms. They feed by extending their arms to catch edible particles that float past.

Phylum Mollusc



One of my favourite slug, the onchidium (Onchidium sp.) comes out only when the tide is low, as they actually breathe air with a simple lung modified from a section of the mantle cavity. The lung opens through a pore alongside the anus at its back end below the mantle. More closely related to the land snails than the sea slugs, most onchidiums hide in air pockets among rocks during high tide, but it was noted that some can also breathe a little through its skin (or mantle) under water.



There were also a few spider conches (Lambis lambis) among the coral rubble. A spider conch has a long trap door (aka operculum) which allows it to hop around like a pole vaulter.



This is a venomous snail called a cone snail (conus sp.) . So do avoid picking up shells that you can't identify, as they can kill you! The cone snail has a modified radula used like a harpoon to stun their prey.



This giant topshell (Trochus niloticus) is about as 15cm tall! Sadly, this shell is often collected and polished to remove the dull outer shell layer to reveal the beautiful "mother-of-pearl" layer. It will then be sold at souvenir shops or cut into buttons.



Cowries (Family Cypraeidae) are greatly sought after by shell collectors, which leads to the extinction of some species in some countries. Not sure about the ID for the one on the left, but the one on the right is probably a gold-ring cowrie (Cypraea annulus). These shells were once used as a form of currency in some countries. The mantle (outer layer of body) covers the shell during movement and secretes pearl-like substances to maintain its glossy appearance.



I also found several species of nudibranchs - from top-left clockwise, we have an Atagema intecta, an unknown nudibranch, a Discodoris lilacina and a Phyllidiella nigra. The name nudibranch actually means "naked gills", which you can see on the back of the 2 nudibranchs on the right (the flowery thing).

One interesting fact about nudibranchs is that they are simultaneous hermaphrodites, meaning each of them has both male and female reproductive organs. They usually fertilise each other when they mate, though sometimes, one may take on a male role, and the other a female role.



That's yet another nudibranch which I have not seen before. Didn't have the time to look through Sea Slug forum to check the ID, so if anyone knows what it is, please let me know :)



This lump of thing is actually also a slug - it's a sea hare (probably Dolabella auricularia)! Sea hares got their name from the projections on their front ends which somewhat resemble rabbit ears. They are closely related to snails, and thus they have soft bodies, but they have an internal shell instead of an external one



There were lots of burrowing giant clams (Tridacna crocea) on the rocks too. The mantle within the shell is usually brightly coloured due to the microscopic algae living inside the tissues. These algae photosynthesise from sunlight and the waste metabolic products of the clam, and provide food for it.



We also saw many octopuses (Order Octopoda). These 8-armed shell-less mollusc are the most intelligent of all invertebrates, and have with well developed brains and eyes. They can change their colour to camouflage themselves too!

Phylum Platyhelminthes



There were lots of flatworms too. For the one on top-left, I've seen similar-looking flatworms in Singapore before, but not quite sure what's the exact species name. Going clockwise from top-right, the flatworms are probably Thysanozoon sp., Pseudoceros sp. and Pseudobiceros bedfordi.

While they look flat and harmless, flatworms are actually fierce predators of small animals or immobile ones like sponges. They are also so flat that they can easily creep into small crevices to hunt their prey or escape from predators. Flatworms also have wonderful this fascinating ability of regeneration. A flatworm cut into several parts will each grow into smaller worms.

All in all, this intertidal trip on Tioman was cerrtainly a very fulfiling one. The next time I come to Tioman on my own, I'm definitely going to visit it again!