Sunday, October 28, 2012


Phylum Annelida

Annelids are a phylum of segmented worms. Well known members of this phylum are the earthworms and leeches. The classification of this phylum and related phyla needs further research.

According to reference number 1 below, there are 19 species of earthworm in Singapore, three of which could be native.

Juvenile Malayan Night Heron feeding on earthworm, Botanic Gardens ©Tan KH

Less well known members of this phylum are the polychaete worms (Class Polychaeta), which include the tubeworms. Tubeworms are common in the mudflats of Chek Jawa. They are so called because they build a breathing tube out of their underground burrow. Two main types can be easily distinguished. The one with the leaves or debris stuck to the breathing tube are the Diopatra, while the one without can be any of a wide range of polychaetes.

Moonshell egg case with 2 types of tubeworms, Chek Jawa ©Tan KH



Phylum Mollusca

The members of this phylum are typically called shellfish, but this phylum also includes the octopus, squids, cuttlefish, snails and slugs. Moreover, lobsters, crabs and shrimps are not molluscs, although they are sometimes also called shellfish. Generally, those with 2 external shells are called bivalves (Class Bivalves); those with a single external shell is called a gastropod (Class Gastropoda) and those without an external shell are called cephalopods (Class Cephalopoda). However, things are more complicated than that. E.g. gastropods which lack an external shell, like the slugs, as well as chitons which have a single shell, but are not gastropods.

Class Bivalvia

Bivalves are so called because they have two shells enclosing the soft body. Typical members of this class are oysters, mussels, clams, cockles, etc.

Rock Oyster (Family Ostreidae) at Chek Jawa ©Tan KH. Left: Stuck to rock. Right: Together with Green Mussels

Green Mussels. Left: Sungei Buloh (Perna viridis) ©Lau SY. Right: Chek Jawa ©Tan KH

Class Gastropoda

Gastropods has a single shell enclosing the soft body. Typical members of this class are snails, slugs, nudibranchs (sea slugs), etc.

Volute (Family Volutidae) at Changi ©Tan KH

Telescopium telescopium, Sungei Buloh ©Tan KH

Sungei Buloh. Left: Common Nerite (Nerita articulata) ©Tan KH. Right: Common Nerite with Black Chut-chut (Cerithidea quadrata) ©Lau SY

Sand collar (egg case) of Moonshell or Moon Snail (Family Naticidae) at Chek Jawa ©Tan KH

Left: The introduced Giant African Snail (Achatina fulica) mating at Neo Tiew Lane 2. Right: A garden snail at Mattar Road ©Lau SY


Phylum Platyhelminthes

This phylum includes all the colourful planarian worms, parasitic tapeworms, flukes and other flatworms.

Planarian Worm (Bipalium sp.) at Rifle Range ©Eddy Lee

Tapeworm(?) at Sungei Buloh ©Danny Lau


Singapore Crabs

True Crabs (Brachyurans)

Small crab (probably a sersamine crab) at Sungei Buloh ©Tan KH

Superfamily Dromioidea
Family Dromiidae (Burrowing Crabs)

Superfamily Calappoidea
Family Calappidae (Box Crabs)
Family Matutidae (Moon Crabs)

Superfamily Carpilioidea
Family Carpiliidae

Superfamily Corystoidea
Family Corystidae (Masked Burrowing Crabs)

Superfamily Dorippoidea
Family Dorippidae (Sponge Crabs)

Superfamily Eriphioidea
Family Menippidae (Stone Crab)
Family Oziidae (Forceps Crab)
Family Eriphiidae

Superfamily Leucosioidea
Family Leucosiidae (Pebble Crabs)

Superfamily Majoidea (Spider Crabs)
Family Majidae
Family Epialtidae
Family Inachidae (Velcro Crab, etc)

Superfamily Parthenopoidea
Family Parthenopidae (Elbow Crabs)

Superfamily Pilumnoidea
Family Pilumnidae (Hairy Crabs)

Superfamily Portunoidea
Family Portunidae (Swimming Crabs, Flower Crabs, Mud Crabs)

Flower Crabs (Portunus pelagicus) are one of the crabs commonly sold in marketplaces. They have a distinctive "flowery" pattern on their shell. They are a type of Swimming Crab (Family Portunidae), which also includes the Mud Crabs used for chilli and pepper crab.

Moulted shell at Chek Jawa ©Tan KH

Mud Crabs (genus Scylla) are the type of crabs found on our dining table. Fortunately, the local mud crabs are not as large as the Giant mud crab (S. serrata), which is the one commonly used for chilli and pepper crabs. They belong to the family Portunidae (the swimming crabs). Singapore has three species: Orange (S. olivacea), Green (S. paramamosain) and Purple Mud Crab (S. traquebarica). The Orange Mud Crab has orange claws, the Green Mud Crab has green and orange claws, and the Purple Mud Crab has purple claws.

Left: Green Mud Crab ©Tan GC. Right: Purple Mud Crab at Chek Jawa ©Tan KH

Orange Mud Crab at Sungei Buloh ©Tan KH

Superfamily Xanthoidea
Family Xanthidae

Superfamily Grapsoidea
Family Grapsidae
Family Plagusiidae
Family Sesarmidae (Sesarmine Crabs, Vinegar Crabs, etc)

Family Sesarmidae includes the tree-climbing crabs, which are commonly seen at Sungei Buloh.

Chek Jawa ©Sylvia Chua. Lor Halus ©Lau SY

The most easily recognised are the large Vinegar Crabs (Episesarma sp.). The Singapore Vinegar Crab (E. singaporense) has red claws; the Pink-fingered Vinegar Crab (E. chentongensis) has a pale movable claw and a red unmovable claw; the Violet Vinegar Crab (E. versicolor) has pale or violet claws.

Singapore Vinegar Crab (E. singaporense)

On mud lobster mound. On tree. Both at Sungei Buloh ©Lau SY

On mud lobster mound, Chek Jawa. Eating brown leaf, Sungei Buloh ©Tan KH

Pasir Ris ©Sylvia Chua

Pink-fingered Vinegar Crab (E. chentongensis)

Sungei Buloh ©Tan KH

Violet Vinegar Crab (E. versicolor)

Left: Kranji Nature Trail. Right: Sungei Buloh ©Lau SY

Left: On ground. Right: Cannibalising. Sungei Buloh ©Tan KH

Family Varunidae (Paddler Crabs, etc)

Superfamily Ocypodoidea (Stalk-eyed Crabs)
Family Camptandriidae
Family Dotillidae (Soldier Crabs, Sand Bubbler Crabs, etc)

Left: Soldier Crab (Dotilla myctiroides) and Right: Sand Bubbler Crab (Scopimera sp.) at Chek Jawa ©Tan KH

Family Macrophthalmidae (Sentinel Crabs, etc)
Family Ocypodidae (Ghost Crabs and Fiddler Crabs)

Ghost Crabs (Genus Ocypode) belong to the same family (Family Ocypodidae) as the Fiddler Crabs (Genus Uca). They are so called because they are able to disappear quickly into their burrow when threatened. They are found on sandy coasts. Sometimes, they have one claw larger than the other, but the size difference is not as distinct as the fiddler crabs'. There are two species in Singapore - Horn-eyed Ghost Crabs (O. ceratophthalma) and Common Ghost Crab (O. cordimana).

Horn-eyed Ghost Crabs (O. ceratophthalma) at Changi ©Tan KH

Fiddler Crabs (Genus Uca) belong to the same family (Family Ocypodidae) as the Ghost Crabs (Genus Ocypode). The male is easily recognised by having a claw disproportionately larger than the other. The female has claws of the same size.

Porcelain Fiddler (U. annulipes)
U. dussumieri (probable)
U. forcipata
U. hesperiae (probable)
Rosy Fiddler (U. rosea)
Purple Fiddler (U. paradussumieri)
U. perplexa (probable)
U. rhizophorae
U. tetragonon (probable)
U. triangularis (probable)
Orange Fiddler (U. vocans)

Unid at Chek Jawa ©Sylvia Chua

Rosy Fiddler Crab (U. rosea)

Female at Chek Jawa ©Gerard Francis

Orange Fiddler Crab (U. vocans)

Male Orange Fiddler (U. vocans) at Chek Jawa ©Lau SY. Male and female Orange Fiddler (U. vocans) at Chek Jawa ©Tan KH

Chek Jawa ©Sylvia Chua

Pasir Ris ©Sylvia Chua


Hermit and Porcelain Crabs (Anomurans)

Family Coenobitidae (Land Hermit Crab)
Family Diogenidae

Hermit Crabs use empty shells as shelters because they have a soft body.

©Tan GC

Left: Pasir Ris Park. Right: Changi ©Tan KH



Subphylum Crustacea

The most familiar members of this subphylum are the crabs, lobsters and shrimps. Few people know that woodlice, brine shrimps, water fleas, tadpole shrimps, barnacles, copepods, ostracods, etc also belong to this subphylum.

Branchiopods (Class Branchiopoda)

This class includes the water fleas.

Barnacles and Copepods (Class Maxillopoda)

This class includes the barnacles and copepods. Barnacles are commonly seen along rock surfaces along the coastline, but there are also those which grow on animal surfaces.

Acorn Barnacles (Balanus sp.) at Sungei Serangoon ©Tan KH

Ostracods (Class Ostracoda)

This class includes the mussel shrimps.

Lobsters, Crabs, Shrimps, etc (Class Malacostraca)

Mantis Shrimps (Order Stomatopoda)

Mantis Shrimps look like shrimps, but they have forearms which are like mantis'.

Sandhoppers, etc (Order Amphipoda)

Mantis Shrimps look like shrimps, but they have forearms which are like mantis'.

Isopods (Order Isopoda)

This order includes the woodlice and sea slaters. The latter are also called sea cockroaches although they are not insects.

Sea Slater (Ligia sp.). Left: Changi Beach Park ©Melvin Dionio. Right: Sungei Serangoon ©Tan KH

Lobsters, Crabs, Shrimps, etc (Order Decapoda)

Decapods are so called for having 10 limbs.