Monday, May 21, 2007
Pitcher plants have specialised leaves that form containers with fluid that is able to digest small animals from ants to even vertebrates like rats. The pitchers are an adaptation that allows the plant to survive in poor soils and other environments where nutrients are deficient and where most other plants cannot thrive.
N. rafflesiana produces two types of pitchers: upper and lower. The lower pitchers are produced on branches closer to the ground and are goblet-like, with two 'wings' that may serve to stabilise the pitcher on the ground. They are also much more colourful, with a marbled pattern, especially on the edge of the pitcher. Upper pitchers are slim with a tapered end and are produced on the higher vine-like portions of the plant.
Many small animals meet their doom in the pitchers, but there are also a few which can survive or even make a living from the pitcher plants. Some species of mosquitoes (not the disease-causing types) breed by laying eggs in the pitchers, and the larva feed on the remains of victims in the pitcher fluid. A species of crab spider can also be found which specialises on catching insect prey that approaches the pitchers.
Friday, May 18, 2007
NF#1: The cliffs of Sentosa appears to be wearing a nice pink layer of blush and this is thanks to the iron within the rocks which acts like make up for the cliffs which are actually made of sandstone. Iron reacts with the constant supply of fresh sea water and result in iron oxide which give it the pinkish reddish glow. It's better than Estee Lauder!
NF#2: The giant balls that look like bird shit littering the beach are actually not natural rocks! They are originally part of the sea wall that people built to prevent further erosion of the cliffs. So instead of eroding the cliff, the waves instead erode the sea wall that sacrifice themselves by standing in front of the cliff. Over time, the sea wall breaks down into pieces and then like any other normal boulders, it becomes smoothened and polished by the waves over decades and centuries.
NF#3: These natural toilets for boys and girls in case of urgent calls of nature are actually natural! They are not made by a kind hearted naked hermit crab to cater to your urgent needs. Instead, they were made by waves over hundreds of years, constantly hitting at the cliffs everyday. First they form little nooks then eventually become bigger caves! Over time, you might even find some have broken off from the cliff to form "stacks" like the Broken Soul Cliff 断魂崖 near Shangri-la!
NF#4: These strips of rocks are not the latest dykes or seawalls built by the government to prevent sea level rise. They are again naturally made coastal platforms. Imagine the beach is made of a giant kueh lapis of alternating hard and soft rocks. Eventually the waves will erode the soft rocks leaving the hard rocks that you are stepping on today!
Monday, May 14, 2007
From top-left in clockwise direction, we have the polka dot nudibranch (Jorunna funebris), a marginated glossodoris nudibranch (Glossodoris atromarginata), a bohol nudibranch (Discodoris boholensis) and a pustolose phyllid nudibranch (Phyllidia pustolosa).
NF#2: Nudibranchs are related to snails. Little baby nudibranchs are born with shells, but they lose them when they become adults.
Thoughtful Question: Having a soft body without a shell makes the nudibranch very vulnerable to predators. How do you think they protect themselves?
Many nudibranch secretes chemicals when they are threatened. The chemicals may either make them very distasteful or even toxic!
That's why nudibranchs are not good for the aquarium! The chemicals they release may caused the other animals to be very stressed, or even die!
Some nudibranchs are also able to store the stinging cells of the hydriods or other cnidarians they feed on in their cerata.
Many nudibranchs are brightly coloured to warn the predators not to eat them, and some nudibranchs are also coloured to match their surrounding, which allow them to camouflage from the predators.
NF#3: Nudibranchs are carnivores, each species usually feed on a particular type of prey, which is usually something that can't move, like sponges, ascidians, hard corals, soft corals, sea anemones, zoanthids, peacock anemones, sea pens and eggs of other creatures. Some nudibranchs, such as the Gymnodoris nudibranch (Gymnodoris sp.) also feed on other slugs).
Here is a Gymnodoris rubropapulosa.
Too Much Information:
There are four sub-orders of nudibranchs - Doridina, Dendronotina, Arminina and Aeolidina.
Doridina is the biggest sub-order. You can identify dorids from the flower-like gills on its back. Dorids commonly seen on our southern shores include: Jorunna funebris, Glossodoris atromaginata, Gymnodoris rubropapulosa, Phyllidiella nigra and Phyllidiella pustulosa.
Dendronotids are charactierised by the two rows of branch-like structures called cerata on their backs. One of the dendronotids found on our southern shores is Bornella stellifer (see below).
Arminina is the smallest and most diversified suborder. The body is flattened and elongate with a mantle which extends into an oral veil. The gills are often along the side under under the mantle. One arminids seen on our southern shore is Armina semperi (see below).
Aeolids usually has thin bodies with projections (cerata) on their backs. One common aeolid we've seen on our southern shores is Pteraeolidia ianthina (see below).
How they "smell":
Many nudibranchs have two pairs of tentacles. One pair is near the mouth. The second pair is further back and called rhinophores. Rhinophores are believed to detect chemicals in the hunt for prey and mates.
Nudibranchs are simultaneous hermaphrodites, meaning each slug has both male and female reproductive organs at the same time. They practice internal fertilisation, and do it side-by-side, facing opposite directions. Sometimes, one will act as the male partner and the other as the female. At other times, they may fertilise each other. After mating, they go their separate ways and each lays its egg mass. Nudibranchs usually die after laying their eggs. In some cases, the eggs are laid on or near a food source and the young ) hatch fully developed and commence feeding. In other cases, the young hatch and are carried in the current. They eventually settle unto a food source and continue developing into adults. The juvenile nudibranchs usually have shells, but lose them eventually when they turn into adult nudibranchs.
Adults reach about 20 cm in length and are popular aquarium fishes in marine aquariums. Unfortunately they don't survive well in captivity as they require a constant and quality supply of live coral polyps to thrive, so it's not kind to either buy them from shops or catch them from the wild.
Their long beak-like mouths are made for plunging deep into coral growth to pluck out small polyps and other sessile creatures. The fish's laterally-compressed body also allows it to dash easily into narrow crevices. At the end of its dorsal fin, a large eye-epot may help to confuse would-be predators that the fish is actually some other larger animal or make them aim for the tail instead of the real head.
Sunday, May 13, 2007
Question for visitor: Do you think this looks just like a leaf? That's why it is called a leaf slug!
NF#1: Leaf slugs belong to a bigger group of animials called the sap-sucking slugs. Instead of breaking off bits of sea weed, munching and eating them, leaf slugs pierce a hole in the algae and suck out the cell contents.
NF#2: Leaf slugs are able to keep keep the algae's chloroplasts (the part that contains chlorophyll), which continue to photosynthesise inside the slug and provide the slug with additional nutrients. That's why they look so green! But don't you agree that being green allow them to blend into so nicely with the surrounding seaweed, and that predators will have a hard time finding them?
Corny Joke: If only we can do that as well, we just need to eat some vegetables and then go sun-tanning to get the nutrients we need! Problem is everyone will turn green though... Quite eerie...
NF#3: Leaf slugs are basically snails without shells. They may look soft and defenseless, but they are NOT! The white specks in its colour pattern are in fact what we call glands. These glands can secrete a milky chemical when irritated, which can make it very distasteful for its predators. It is believed they recycle the chemicals from the food they eat.
Too Much information:
Leaf slugs are not nudibranchs! They are from the order Sacoglossa, which nudibranchs are from the order Nudibranchia. Both, however, are mollusks from the same class, Gastropoda. The leaf slug we usually see on our shores is Elysia ornata (see below).
Elysia, as with all slugs, are hermaphrodites. They have both male and female reproductive organs which are located on the right side of the head.
Hints for guides:
Leaf slugs are seasonally abundant on our shores. They usually come and go with the hairy green seaweed, bryopsis, which they feed on. So if you see lots of hairy seaweeds, keep your eyes open.
Here's another species of Elysia which we see sometimes.
NF#2: However, mature trees are known to have a weak structure, and break easily, especially during stormy weathers. Being a roadside tree, it is thus a potential hazard for vehicles and nearby buidlings. This is also probably the reason why this tree looks like this now.
Joke: Ahem, this tree always remainds me of some people I know - those who appear strong and hardly outside, but turn out to be weaklings.
NF#3: Angsana wood is said to be the best fine-furniture wood in Malaysia. It is used to make tables, chairs, cabinets, and decorative items.
Too Much information
You will be quite lucky if you can see the flowers, as they usually last for only one day. The flowers are small, yellow and faintly fragrant. They grow in large bunches 15 to 30 cm long.
NF#1: Built by the British in the 1880s to protect the western entrance to the Singapore harbour, Fort Siloso is the only preserved British coastal fortification in Singapore today. The name 'Siloso' supposedly comes from a Filipino word 'Seloso', which means a jealous person. The original name for Siloso Point was 'Sarang Rimau', or 'The Tiger's Lair', as it was said that tigers used to roam in the area.
Question for Visitors: Have you hear about the story that the Singapore Guns were facing the wrong way (south) when the Japanese attacked Singapore from the north during World War II?
NF#2: This is not true. The guns were not facing the wrong way, but the forts themselves were wrongly located for an attack from the north. The British had assumed that the defense in the north will be well-covered by Peninsular Malaysia. According to records, most of the forts, including Fort Siloso, took part in the battle.
NF#3: The fort complex is often incorrectly described as a tunnel complex, though in actual fact there are no real tunnels at the Fort, but underground chambers. There were stories that there are undersea tunnels that join Sentosa with Labrador Park. However, no one has been able to proof this so far. There are lots of natural caves along the coast of Sarang Rimau though.
Too Much Information:
The Fort was a POW Camp until the end of World War II. When the Japanese surrender in 1945, Fort Siloso returned to British occupancy, and in September that year, it was initially used by the Royal Navy.
The fort was opened to the public as the Singapore Gun Museum in 1975, and the buildings, underground complexes and gun emplacements both wartime and from the early days of Siloso are very well preserved, although some areas were changed to allow ease of access by tourists.
The juvenile catfish form a virtual ball that swarms over the reef flat as they wander around seeking both food (probably small crustaceans) and shelter. There doesn't appear to be any 'leader' of the pack but they always move about cohesively and defy any attempt to split the group up.
Don't try to touch the catfish though, even if they are mere inch-long fry. They possess venomous glands in the pectoral and dorsal fin spines that can cause very painful wounds. However, they won't attack or sting unless one is silly enough to handle them.
Plotosus lineatus is probably the only catfish species to be found in coral reefs. It's a wideranging species, found all over the Indo Pacific and Indian Oceans.
Friday, May 11, 2007
NF#1: The marine spider can really live in the sea! At high tide, it waits in air pockets among the submerged rocks or coral rubble. At low tide, it comes out to hunt! This one has caught a little shrimp!NF#2: The spider can 'walk' on water! Its furry feet repels water. But it doesn't really move very well over water, preferring to forage on dry ground.
NF#3: Threatened spider: The marine spider is listed among the threatened animals of Singapore due to habitat loss.
Hints for Naked Hermit Crabs
These small spiders (1.5-2cm) are quite common. They are more active near dawn or dusk. Look for unusual movement among the rubble.
Thursday, May 10, 2007
Giant reef worm (Eunice aphroditois)
This worm can reach 1 metre or longer! Although it looks fierce and scary, it is a scavenger and eats seaweed too. But it can give a nasty bite so do leave it alone.
Corny joke: It has a face that only a mother could love!Hints for Hermits
Giant reef worms are particularly common on Sentosa. They usually live in the large piles of coral rubble, zooming out to snatch a mouthful of seaweed or other titbit before retracting immediately into their hiding places.
Flatworms are ...err... really flat! This large (8-10cm) black flatworm with little spots (Acanthozoon sp.) is commonly seen. It can swim by flapping the sides of its body!Hints for Hermits
Flatworms are EXTREMELY fragile and will disintegrate if handled. They move very quickly too and can disappear in an instant into some crevice.
Bristleworms (Class Polychaeta) are very bristley indeed. Some have glass-like bristles that introduce painful toxins into the skin. These worms are sometimes called fire worms.Hints for Hermits
Bristleworms are sometimes seen in numbers, especially early in the morning. They move actively about. Needless to say, we shouldn't touch them!
Fanworms (Family Sabellidae) Some worms are beautiful! A fanworm has a long wormy body that is tucked into a leathery tube. At the top of its head, there is a feathery fan made up of modified tentacles. Hints for Hermits
Fanworms are found among coral rubble, sometimes in living corals. They are very shy and will instantly disappear at the slightest sign of danger. Have your visitors keep still (avoid casting shadows or splashing around) and the worm might come out again.
Stuck in a shelter waiting for the rain to stop? Came too early and the tide is still too high to go out to the flats? Here's some stories of death and violence to entertain your restless visitors with.
First go out and quickly gather some of these shells that tell the story.
(The striped stick at the top left corner is a spine of a sea urchin. Living sea urchins are covered with a skin. When they die, the skin rots and their spines fall off)
Snail shells are generally coiled. (Show some other broken shells of typical snails with their coils exposed).
The cowrie doesn't look like it has a coiled shell from the outside. But inside, it is coiled!
Thoughtful question: Why do you think the top of this cowrie shell is broken?
It was probably crunched off by a hungry crab!
All these shells have similar breaks at the top.
Thoughtful question: What do you think happened to them?
You're right! A crab probably crunched them too!
Many snail-eating crabs have two different kinds of claws. One large crunching claw, and another claw with thin pincers that act like chopsticks to pick out the snail snack.
See the hole in this clam shell? And the break in the other?
Thoughtful question: Oh dear! What happened to these clams?
The hole was probably drilled by a clam-eating snail, like a moon snail. The moon snail produces an acid that softens the shell. It then uses its rough file-like tongue to slowly drill a hole. The clam is then pumped with digestive juices and is sucked up like soup. Yummy!
The big broken clam was probably crunched by a crab.
Thoughtful question: Do you think these two snails are of the same kind? Or are they different?
On the right is the Dwarf turban snail (Turbo bruneus, Family Turbinidae)
On the left is the Toothed top shell snail (Monodontia labio, Family Trochidae)
NF#1: To tell them apart, look at their undersides!Two different ways to keep out nasty crabs!
NF#2: Thick door is good On the right is the Dwarf turban snail (Turbo bruneus). The door to the shell opening (operculum) is thick and rounded. The smooth rounded surface makes it difficult for crabs get a grip. And the thick operculum is hard to crack.
The hemi-spherical operculum is called a 'cat's eye'. Sometimes you may come across loose 'cat's eyes' on the beach washed up from dead turban snails.
NF#3: Thin door works too On the left is the Toothed top shell snail (Monodontia labio). It has a single 'tooth' at the shell opening ('Mono'=one and 'dontia'=tooth). Its operculum is thin and flexible. The snail can pull the operculum deep into the shell to make it difficult for crabs to dig them out.
Shells protect snails from all kinds of dangers.
Thoughtful question: Can you think of an animal that might want to eat this snail? How about other things that can harm the snail?
Thoughtful question: Let's look at its shape. What does it remind you of? How does this shape help protect the snail?
NF#1: Shell shape: Round and smooth like half a marble, this streamlined shape allows the snail to avoid being washed off the rocks when it is splashed by waves and swept by currents.
It also makes it difficult for a crab to get a grip on the slippery smooth shell, or to crack it. Like a marble, the snail is likely to slip out of the crab's pincers and bounce and roll away!
NF#2: Shut the door! When it is in danger, the snail can quickly retract into its tough thick shell. It also hides in its shell to stay wet, when it is hot and dry outside.
To cover the hole in the shell, it has a tough door (operculum). In nerites, the operculum has an internal peg to lock firmly in place. This makes it difficult for a crab to stick a pincer in and dig out the snail.
NF#3: Colours: Although some shells are colourful, these snails are hard to spot as they blend well with the colourful rocks where they are found.
Thoughtful comment: Shells can be very pretty. Many people collect pretty shells and don't realise how beautiful the living animal is. See, this snail has a striped body! And such cute long tentacles.
Did you know that shells sold in souvenir shops are taken from living snails? The snails are killed for their shells! So please don't buy shells.
Hints for Naked Hermit Crabs
Where to find them? During the day at low tide, nerites usually hide in crevices and shady spots. At night and on a cool wet day, you might see them creeping about on rocks and boulders, especially those covered in algae.
After having a look at a nerite, be sure to put it back where you found it. And make a big deal about doing this. So visitors get into the habit of doing the same.
Often, if you leave a nerite alone upside down on a rock in a shady spot, it will eventually come out. You can then talk about the living animal and not just the shell.
Too Much Information
What do they eat? Nerites graze the thin layer of algae that grows on rocks.
Nerite babies: Nerites have separate genders and engage in internal fertilisation. So they actually have to make body contact to reproduce. Sometimes you can see mating nerites, especially early in the morning, near wet spots on a rock. The eggs are laid in white circular egg capsules. Each egg capsule may have more than 30 eggs.
What are the different kinds of nerites commonly seen on our shores?
A rough identification can be made by looking at the shell's general shape and texture, and especially the underside of the shell and the teeth-like structures at the shell opening (these do not actually function as teeth to chew food). But similar nerites can only be positively distinguished by looking at internal features of the shell and animal.
Ox-tongue nerite snails (Nerita albicilla)
2-3cm. Shell rounded but flared at the mouth, with faint grooves on the upper surface. On the underside of the shell, on the flat portion in front of the shell opening, there are a series of obvious bumps. This surface resembles the tongue of an ox, hence its scientific name. This nerite is not as commonly seen as the following two.
Chameleon nerite snails (Nerita chamaeleon)
2-3cm. Shell sturdy and rounded with a more flattened spire and rough grooved lines on the upper surface. It has very small 'teeth' near the centre of the shell opening. Some have a row of 4 bumps perpendicular to the edge of the shell opening. It comes in a wide variety of colours and patterns, hence its name. It can be seen in large numbers on some of our rocky shores.Waved nerite snails (Nerita undata)
2-3cm. Shell sturdy and rounded, with a more pointed spire and fine smooth grooved lines on the upper surface. The flat area near the shell opening is white with 3-4 distinct 'teeth'. It comes in a wide variety of colours and patterns. It is found together with Chameleon nerite snails, also in large numbers.Lined nerite snails (Nerita lineata)
2-3cm. Shell sturdy and rounded. It is distinguished by the grey shell with neat black grooved lines. It has small 'teeth' at the shell opening. It is more often seen in and near mangroves. Look for them closer to vegetation and in shady areas nearer the high water mark. The scientific names given here are the old ones. Recent books give different genus and species names to some of the snails. I've yet to get confirmation on the current names.
NF#1: Sponges are animals! It's OK if you thought sponges were plants. In fact until about 100 years ago, early scientists also considered them to be plants.
NF#2: Sponges vacuum food out of the water. A sponge sucks water into its body and traps edible bits in the water flow. A sponge can filter water many times its body volume in a short time. In general, a sponge can pump water equal to its body volume once every 5 seconds!
NF#3: Sponges are not softies: Although they look soft and are generally immobile, sponges are not as defenceless as they appear. Many sponges have tiny hard spikes throughout their body. Some spikes are like glass needles. In addition, some sponges release chemicals that irritate other creatures (including other sponges) and prevent them from growing over the sponges. Others contain chemicals that taste bad or are toxic, so animals won't nibble on them.
Some sponges might give you a rash. So please don't touch the sponge!
(Possible Visitor Question: But what about bath sponges? The natural bath sponge is a special kind of sponge that does not have nasty spikes. )
In fact, sponges are so well defended that small animals may live inside and on a sponge. These animals also get free 'air-con' from the flow of water generated by the sponge!
Interactive activity: let's see what animals live on this sponge?
This brown sponge is quite commonly seen on Sentosa. It is usually riddled with tiny brittlestars, one brittlestar in each hole, with only its tiny hairy arms sticking out. During the day, however, the brittlestars are usually well hidden and it's hard to see them.
Too Much Information
Besides Naked Hermit Crabs, ordinary people probably won't soak up this information like a sponge (oops...spontaneous corny joke).
A sponge is a simple animal made up of a few types of cells. These cells are largely independent of one another and only loosely held together. These cells do not form tissues or organs, so a sponge does not have a mouth, digestive system or circulatory system.
A sponge is NOT a colony! In the way that a hard coral is a colony of individual animals.
Why are sponges so colourful?
Scientists don't really know why. One suggestion is that the vivid colours of some sponges warn of their toxic or distasteful nature. The colours might also be a kind of sunblock that protect from harmful rays of the sun. Some sponges harbour symbiotic algae that may colour them green, violet or brown.
Some sponges commonly seen on Sentosa
A yellow to brownish sponge with several 'cones'. When out of water, the cones collapse into mounds. If you come across a large submerged sponge, look for the tell-tale signs of the current of water generated by the sponge.
This encrusting sponge can cover an area of 20-40cm of coral rubble and other hard surfaces. Sometimes branches from out of the encrusting base. The surface of the sponge has prickles. It may be yellow, orange, brown or greenish.This sponge resembles a pot! Usually somewhat oval and squat with one or more depressions in the centre, and lumps on the outside. May be yellow, orange or brown.
This sponge forms a smooth layer over coral rubble with irregular bumps and ridges. It has tiny holes. It is usually blue, sometimes violet or greenish.This tiny pink puff (1-2cm) is a sponge! Usually one or two on coral rubble.
NF#1: Sea slaters are NOT cockroaches. They are not insects. They are more like crabs and shrimps (They are crustaceans.)
Sea slaters can be quite colourful and pretty if you take a closer look at them.NF#2: Sea slaters move very fast!
Thoughtful question: How many legs do you think the sea slater has? Any guesses?
They have seven pairs of legs! They have huge eyes and very long antennae. They also have a pair of long 'tails'. So sometimes it's hard to tell which is the front and which is the back end of a sea slater.
Sea slaters only come out at low tide. They are well adapted for life out of water, breathing air directly through 'pseudo-lungs'. In fact, they will drown if kept under water for a long time!
NF#3: Sea slaters help keep the beach clean. They are scavengers, nibbling on whatever recently died on the shore. At low tide, they swarm over the rocks hunting for food. Thus anything that dies on the beach is quickly cleaned up. It's a natural process of recycling.
Corny joke: Don't worry. Sea slaters won't bite or eat you. Unless you are dead.
But sea slaters can't eat up plastic, glass, metal or other man-made litter. There is no natural process to clean our rubbish! We should not litter.
Hints for Naked Hermit Crabs
Sea slaters are often the first things visitors see. Some people may freak out, especially those with a phobia for cockroaches; and if the swarms of slaters are very large.
It's probably best to explain what sea slaters are as early as you can, to pre-empt any hysteria.
I don't know how to catch a sea slater without hurting it or myself in the process. But I find it's easy enough to talk about them even if you don't have one at hand.
You could tell everyone to stand still so the sea slaters come out. This is also a good excuse to get them to practice quiet observation.
Thoughtful question: What does this remind you of? Fried eggs? Surgical gloves?
Corney joke: Don't they look like life from another planet?!
NF#1: Leathery soft corals are a colony of animals. Each animal looks like a very VERY tiny sea anemone with a long body topped with tentacles. The animal is called a polyp. Countless polyps live together in a shared leathery tissue.
Interactive activity: Please don't touch the leathery coral, but let's take a closer look at the surface. Can you see the polyps?
Portions still underwater may have polyps sticking out, and look 'furry'. When exposed to air at low tide, the polyps retract into the leathery tissue. This leaves a smooth surface, with only tiny holes where the polyps are.NF#2: Leathery corals are not softies! Leathery corals are generally not welcomed in a marine tank because they produce substances that stunt or prevent the growth of hard corals nearby. That's why it's probably also best not to touch them.
Too Much Information
Only for the information of Naked Hermit Crabs...
What do they eat?
Some leathery corals harbour inside their bodies, microscopic, single-celled algae (called zooxanthallae). The algae undergo photosynthesis to produce food from sunlight. The food produced is shared with the coral, which in return provides the algae with shelter and minerals.
What are the different kinds of leathery corals?
Leathery corals of the Family Alcyoniidae may have two kinds of polyps.
Autozooids have long stalks with tiny tentacles that emerge from the skin. There are 8 or multiple of 8 tentacles, and the tentacles are feathery.
Siphonozooids don't emerge from the skin and function as water pumps for the colony. They look like bumps on the skin.
The different kinds of leathery corals are distinguished by the kind of polyps they have, not only by the shape of the colony.
Sinularia leathery corals (Sinularia spp.) have only autozooids and do not have siphonozooids. A colony can take on a wide variety of shapes and even the same species may have different forms.Omellete leathery corals (Sacrophyton spp.) have both autozooids with long stalks and siphonozooids. A colony is usually mushroom shaped with a stem or stalk attached to a surface or buried in the sand. The top of the mushroom may be extensively folded so the colony appears flower-like.Lobed leathery corals (Lobophytum spp.) have both autozooids and siphonozooids, but the autozooids have short stalks and often appear as mere tufts of tentacles. A colony is encrusting, that is, the upper surface is the same diameter as the colony base and they do not have a stem or stalk. It may be dish- or bowl-shaped. The colony is thick and generally has lobes, ridges or rib-like structures.
Thoughtful question: What are these? Animal/plant/mineral?
The answer? You’re all correct!
NF#1: Corals are colonial animals - they clone themselves to form colonies that look like the boulders you see around you! The individual is called a 'polyp' and it looks like an (small) anemone! Animal characteristics include eating and breathing. In the water, especially at night, they extend their tentacles to feed, amongst other things... (like coral warfare - see below for Too Much Information)
NF#2: They are plants too! Like their other sting-ey cousins, corals also contain tiny algae within their tissues called zooxanthellae, that make food from light to share with their polyp hosts. The zooxanthellae are also what give them their pretty colours. If the water temperature gets too hot and the corals get stressed, the zooxanthellae will leave the corals (well it's not currently clear whether they leave or are kicked out or it's mutual), and the corals will 'bleach' - turn a white colour. Bleached corals may eventually recover, if the conditions become favourable and they can survive the stress.
Corny joke: Corals aren't the only things that get bleached. Blonde coral jokes, anyone?
An interactive activity: How do you tell a dead coral from a living one? (Tell them to be careful where they step!)
NF#3: So where’s the mineral part? Each polyp builds a hard skeleton for protection, where it lives in – just like people live in flats. That would make the colony a block of flats! At low tide, the polyps hide inside to keep from drying out. Actually only the thin layer on top remains ‘alive’, this layer can easily be damaged from careless contact, so be careful where you step! Underneath, the dead skeleton (white if freshly exposed, but soon gets covered over by silt and algae growing) left behind is what forms the coral reef structure. Like trees in the rainforest, this structure is where all the other reef animals live!An interactive activity: How about a bleached coral from a (recently) dead one? (Think about it...a dead coral would just be the skeleton, so you wouldn't be able to see the tissue.)
Colony, and close ups of dead and living sections. The bits of colour in the centre of the dead section are the remains.
Thoughtful question: Why do you think there’s usually a ‘botak’ patch on the top of the coral? What is different about the top and the sides?
How NOT to hug a coral
As living corals are very easily damaged, careless contact by clueless humans can harm or kill them. It is best not to touch the corals at all – this means no poking, or kicking. And be careful where you step!
Helpful hints for Naked Hermit Crabs ...
Everywhere on the lower shore.
Too Much Information!
Only for Naked Hermit Crabs who want to know Don't force feed this info to visitors! They may fall asleep if you do.
What types are there? – a quick and dirty coral ID guide for the coral rookie
Lots of types, sorted visually by growth forms (branching, massive rock-like), the way the patterns on the coral look (brain, maze, round, little holes).
Anemone Coral (Goniopora sp.) has long fleshy polyps that extend out of the skeleton
Plate or Disc Coral (Turbinaria sp.) is plate-shaped, with large polyps sticking out.
Mushroom corals (Fungiidae) - Free-living species are not attached to the reef, unlike most other corals
Branching corals: Pocillopora damicornis (top) and Montipora sp. (bottom)
Stone Corals (Faviidae) are usually shaped like boulders – though there are other kinds shaped like boulders too…
What do they eat?
They get most of their nutrition from their zooxanthellae. Or they also eat plankton, caught from the water using their tentacles.
The secret world - sex and violence (RA!)
How do rooted things make luuuuurve? Like most marine creatures that don’t move around, corals simply release their eggs and sperm into the water! Tide and currents take care of the rest. This is a very coordinated event, in terms of timing, to ensure that spawn from different colonies meet and mix.
Mass spawning is an event happens within the time frame of 2-3h on a few nights every year, where many types of corals (and some other reef creatures too) release their eggs and sperm at the same time! On bigger reefs, this can form spawning slicks on the surface of the sea – like an oil slick but consisting of coral eggs and sperm bundles.
Scientists are still trying to figure out how this extraordinary coordination occurs. The baby corals (like little anemones, or jellyfish) drift on the currents, and eventually settle in a suitable place. The baby polyp will build its home there, and start building a whole new colony!
Colonies spawning (2 photos), and close up of Galaxea egg bundle.
Look for bands of silt-covered dead coral between neighbouring colonies, usu a few cm in width, and quite uniform. This is evidence of coral warfare. On the reef, competition for space can get quite violent, and many corals have special, extra long war tentacles that they use to zap other corals into submission. They then take over the space vacated.
This is an interesting question to answer, with regard to colonial animals. It depends on the definition of ‘life’ and ‘the individual’. Because coral polyps divide over and over again, producing essentially the same individual, external factors like predation, disease and environmental conditions aside, they can ostensibly live forever!
Directly, coral skeletons (calcium carbonate) have long been used as building material in less-developed places. Coastal reefs are also thought to protect their coastlines from storms.
Indirectly, coral reefs are the habitat and nursery ground of many kinds of seafood. So no corals = no seafood.
Blue coral is a kind of "coral" that has an internal blue skeleton. It's not really a hard coral, as it belongs in the sub-class Octocorallia, along with the soft corals, whereas the hard corals lie within the subclass Zoantharia, which also includes the anemones.
Corals are quite sensitive to environmental changes, and can only survive within a small range of temperatures and light levels. The recent increase in global temperatures have caused major coral bleaching problems throughout the world in the last decade. This is bad because bleached corals lose their helpful algae symbionts and are prone to die off. You can help the corals by doing your part to live sustainably!