Friday, April 2, 2010

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

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