Guided walk at Semakau on a stormy afternoon

We were back at Pulau Semakau on 4 Apr, for a guided walk with the students from Tampines Sec. Upon reaching the island, the looming dark skies spells of bad weather.

The perfect timing saw us seeking shelter at the entrance of the secondary forest - just as we reached the entrance point after the walk from the Visitors' Centre, the rain started pouring! Our hunter-seekers were already ahead of us, and I wondered if they too were seeking shelter in the forests.

After almost an hour, the rain though subside, continues to fall. The students, however, were not daunted a single bit and were really eager to start the walk.

With the absence of thunder and lightning, we braved the rain with our ponchos, for an hour of marine adventure.

Unfortunately, the first sight that greeted us was a drift net placed by irresponsible people. It had caught several fishes that were already dead. Drift net fishing not only results in unsustanable fishing, it also causes unnecessary harm to other marine animals that fishermen do not intend to catch. I shared the intention of Project Semakau with the participants, who concurred with the idea of gazetting the shore of Pulau Semakau as a protected area.

We visited the resident Anemone by the edge of the seagrass lagoon. Unfortunately, we didnt see the Anemone shrimp taking shelter under its usual host. The Anemone may look harmless, its lashing tentacles have stinging cells that may cause pain and discomfort to the skin.

Trotting on, I was glad to see the usual suspects at the sandy shore. The Sand-sifting Sea Star (Archaster typicus) is a good burrower of the sand (thus its name) and has a water vascular system to bring nutrients and oxygen through its body, unlike the blood circulation system in human beings. 

My heart almost sank when I saw the Hairy Crab (Pilumnus vespertilio) at one of the stations. The hunter-seekers had prewarned us that the showcase of a Hairy Crab at a station indicates the desperation of the unsung hero(ine)s. We couldnt ask for more, because animals were pretty much hiding after the downpour.

Named after its hairy appearance, this crab is slow in movement as compared to other crabs. To make up for the speed, its appearance allows it to camouflage really well both in water and on land.

Kudos to some keen eyes, the less common Heart Cockle (Corculum cardissa) was spotted! A bivalve, the Heart Cockle's 2 valves are separated by an opening that cuts through the middle. A victim to over-collection of its shell, it is often marketed as a token of love sometimes at a fairly cheap price, thus popular among couples.

A Ovum Cowrie (Cypraea ovum) was also seen moving along the surface. Another victim of over-collection, its shell was once used as a form of currency in the past. I wondered how that money system worked though, nonetheless glad its no longer the case else this snail would be extinct by now! The cowrie maintained its smooth and pretty shell by covering it with its own mantle, which protects the shell from any abrasion and scratches.

Not sure what the common name is, but the very uninnovative me calls it the Green Nudibranch (Ceratosoma sinuatum). Nudibranchs are named after the naked gills exposed at its back, which it uses to breathe. Interestingly, they are actually hermaphrodites, possessing both the male and female reproduction organs.

I was really happy to see the Cushion Star (Culcita novaeguineae) that is no longer as juvenile as a few months back. In its teenage months, this individual has clearly become rounder. This shape, coupled with a calcified body, makes it difficult for predator to prey on it. Hope that it will soon grow into a healthy adult!

Thanks to the hunter-seekers who braved the storm to find us a Knobbly Sea Star (Protoreaster nodosus), often the highlight of any guided walk. This species of Sea Star, named after the knobs on its body, is endangered on our shores and has fallen victim to the aquarium trade. I once saw one in a store at Plaza Sing, clearly looking undernourished. Human beings is one 'predator' that the calcified Knobbly cannot run away from.

The Fan Worm (Sabellastarte indica) was one of the few who gamely displayed its beauty on this rainy morning. Its feathery tentacles opened broadly, looking just like a fan and was probably lashing through the water for very tiny food particles. The tentacles is often the only part of the fan worm that is exposed as it lives in a self-made tube of its own mucus, sand and particles. Any detection of danger results in the tentacles retracting into the tube at lightning speed, which often wowed the participants.

Despite the bad weather, we still managed to experience the life of our shores. The participants' spirits were not dampened, instead are more willed to visit our shores again for more exciting encounters.

First guided walk at Pulau Hantu - 2 Apr 2010

My first public walk of the year was at Pulau Hantu. My group consists of participants who were not new to intertidal walks as they have joined us on walks at Pulau Semakau previously. Their enthusiasm and interest in nature made guiding very much enjoyable!

The island is actually made up of two islets: Pulau Hantu Besar (Big Ghost Island) and Pulau Hantu Kechil (Little Ghost Island), and is aptly named as "island of ghosts". It was here that 2 great ancient Malay warriors dueled fiercely to their death. The gods then transformed the two warriors into islets and their ghosts are said to wander the isle.

Warriors wannabes?

Despite its proximity to the Pulau Bukom's refineries, a wide variety of corals can be found on Pulau Hantu coupled with fairly rich marine life. Our first star (pun not intended) of the day was the Sand-sifting Sea Star (Archaster typicus). These 2 individuals had a few shorter arms probably chomped off by predators. Although they can regenerate their arms, it is a long process and I would imagine it to be quite an unpleasant experience.

We were thrilled by the male Fiddler Crab's (Uca spp.) morning greetings. It was really quite a spectacular sight to see them waving their enlarged claw, as if playing the fiddler. Not sure if it was the mating season, but they sure were eager to capture attention. We even saw 2 fighting each other, likely for territory or a mate. The enlarged claw is a great asset in courtship, as females are likely to be attracted to those with larger claws since it is quite a feat to be able to survive with this 'liability' which requires more to maintain.

 

The Hairy Crab (Pilumnus vespertilio) attracted praises of  'so cuuuute' as it hid in one corner of the container. Also fondly known as the Teddybear crab to some, the Hairy crab got its common name from its appearance. The hairs fluff up when the crab in water thus breaking its outline and results in some really good camouflaging performance. Note that this is not the Hairy Crab some Chinese deem as a delicacy, in fact, this crab is mildly poisonous.

The Orange Striped Hermit Crab (Clibanarius infraspinatus) was quite shy that day, and there wasnt time to wait for a nice photo opportunity. Unlike real crabs, the hermit crab actually has a soft abdomen thus requires the protection of an empty shell as its home. So, think twice when you next think of collecting an empty shell from the shore 'cos you may be depriving our friend of its potential home.

My guests laughed when I asked if the Black-lipped Conch (Strombus urceus) reminded them of a woman's lips with black lipstick. Like other Conches, the Black-lipped Conch also uses its operculum to hop along the surface.

The Spider Conch (Lambis lambis) is named so, after the spikes on the sides of its thick shell, resembling the legs of a spider. The conch's humble appearance makes it difficult to spot among its home, but turn it over, you will be awed by its pretty shell, just like many of our participants were. Apart from being a master of camouflage, the Spider Conch is a great pole vaulter with the use of its knife-life operculum to hope along the surface.

This is a probably a Wandering Cowrie (Cypraea errones) strolling around, 'feeling' and 'tasting' the water with its siphons. This snail is a great master at maintain its looks. See the shiny and smooth shell without scars and scratches, all thanks to its intelligence use of its own mantle to cover its shell. While I have all praises for the cowrie, I wish its shell wasnt as pretty to prevent it from being a victim of over-collection.

 

Nudibranches never fails to fascinate me with their bright colours. 'Nudi' is translated as naked in Latin and 'Branchia' as gills. The Nudibranch's naked gills (see the feathery structures) is thus what gave its name. This sea slug actually possesses a shell when young, but sheds it thereafter. It thus develops defense mechanisms such as bad tasting glands, and depicts the poison through its bright colours to warn predators.

Heres the pretty Chomodoris lineolata.

   

The colours of the Black Margined Nudibranch (Glossodoris atromarginata) were also fascinating.

   

While the Phyllid Nudibranch (Phyllidiella pustulosa) may look puny and cute, it is actually deadly to other marine life. Try placing this nudibranch in an aquarium , stress it and the entire tank could be wiped out by the milky substance it secretes. This is typical of its family which feeds on poisonous sponges, and concentrate the toxin in its tissues as a defense mechanism.

    

An animal that many people can recognise at first sight, the Jellyfish (Chrysaora sp.) can sometimes be seen at our popular beaches at Changi or East Coast. One should avoid touching one though, because of its stinging tentacles. A friend had complained of discomfort after being stung by a jellyfish during her swimming lap of a biathlon.

   

Giving us the Puss-in-boots looks was this Octopus (Order Octopoda), known to us as one of the smartest invertebrates that can recognise its tracks and even open the lids of jars. Another master of camouflage, it can change its colour and even texture of skin to match that of its surrounding within the snap of the finger, all thanks to special pigment cells.

My favourite of the trip was this Red Feather Star (Class Crinoidea), although it reminded me of the feather duster my mum used to cane me with. Although it has a mouth in the middle of its top surface, the Feather Star feeds by filtering small particles of food from the sea water with their feeding feathery arms. Like other echinoderms, the Feather Star has a symmetry of 5 - this individual apparently has 25 arms (go on, count it!).

Right beside the Feather Star was a humble looking (and therefore very well camouflaged) Onch slug (Family Onchididae) that I did not spot, if not for Ruixiang's obvious hint. Breathing through simplified lungs, this slug is more related to land snails and slugs. Its often seen on the surface of rocks as it is where it finds algae, its source of food. Without a hardy shell, the Onch slug secretes a supposed bad tasting mucus that covers its skin to ward off predators.

An intertidal trip is always precious and never possible for one to see everything. Apart from having to abide by the rules of the changing tides, our marine life roams freely and is thus never predictable. Such is nature, but this also make every experience special and unique. Come explore our shores and sign up for the next available trip!