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Phylum Arthropoda | Subphylum Crustacea | about moulting
Crustaceans
Subphlum Crustacea

updated Dec 08

if you learn only 3 things about them ...
Crustaceans are the largest group of marine arthropods.
Surprising crustaceans include barnacles, sea slaters.
Crustaceans belong to Phylum Arthropoda which includes insects, spiders, centipedes.

Crustaceans are among our favourite seafood! Having to personally dismantle some of these creatures to eat them, many of us are more familiar with them than we might imagine.

What are crustaceans? If crustaceans remind you of insects, they are indeed related and belong to the same Subphylum. Together with more familiar creatures like spiders and centipedes, they all belong to the Phylum Arthropoda. Crustaceans are the largest group of marine arthropods. There are about 45,000 known species of crustaceans. More than 80% of these are marine.

Arthropods have a hardened outer skeleton (exoskeleton) called the cuticle. They have jointed legs. Arthropods make up nine-tenths of all known animals, so this body plan seems to work well.

Crustaceans come in a wide range of body forms. Some adults are so unlike 'typical' crustaceans that it is hard to believe they are related to familiar creatures like shrimps and crabs. These include barnacles, often mistaken for oysters or limpets, and parasitic barnacles that invisible for most of their lifecycle! Sea slaters scurry about by the hundreds over rocks at low tide and are often mistaken for insects or cockroaches. They are, however, crustaceans just like crabs and prawns.

One crustacean characteristic that distinguish them from other arthropods is that at some time in their life cycle, crustaceans have two pairs of antennae. All other arthropod groups only have one pair. Most crustaceans have limbs that are branched (biramous), while other arthropods don't.

Classifying Crustacea: Nearly 60% of crustaceans fall into the Class Malacostraca. Most malacostracans (10,000 species) belong to the Order Decapoda.

Class Malacostraca
  Order Decapoda
  Brachyurans true crabs
Anomurans hermit crabs; porcelain crabs
prawns and shrimps, lobsters
  Order Stomatopoda mantis shrimps
Order Amphipoda amphipods
Order Isopoda sea slaters

Class Cirripedia barnacles

Class Ostracoda mussel shrimps
from Edward E. Ruppert, Richard S. Fox, Robert D. Barnes. 2004.Invertebrate Zoology Brooks/Cole of Thomson Learning Inc., 7th Edition. pp. 963


Crusty cast-off:
Like other Arthropods, crustaceans have to shed their hard outer skeleton (exoskeleton) in order to grow bigger. The process is called moulting and is quite fascinating. More about moulting.

Human uses:
Crustaceans are eaten by people everywhere. Barnacles grow on any surface in the sea, including ships, water pipes and other important infrastructure. Thus these tiny animals can affect human activities in a big way.

Status and threats: Sadly, many of our beautiful and fascinating crustaceans are listed among the endangered animals of Singapore. Like other marine creatures, they are vulnerable to habitat loss due to reclamation or human activities along the coast that pollute the water. They are also vulnerable to trampling by careless visitors and over-collection for food and for their shells can affect local populations.

Crabs are among the more familar crustaceans.
Sentosa, Aug 04


Prawns are crustaceans too.
Pulau Hantu, May 05


Barnacles are crustaceans!
Labrador, Apr 05


Mussel shrimps are tiny crustaceans
that give off blue bioluminescence
Pulau Sekudu, Aug 05


Horseshoe crabs are NOT crustaceans!
But they are arthropods.
Changi, May 05

Crustaceans on Singapore shores
text index and photo index of crustaceans on this site

Threatened marine crustaceans of Singapore
From Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore.

True crabs (Marine)

  Family Calappidae
  Calappa sp. (VU: Vulnerable)

  Family Carpiliidae
  Carpilius maculatus (Spotted reef crab) (EN: Endangered)

  Family Corystidae (Masked burrowing crabs)
  Gomeza bicornis (VU: Vulnerable)
Jonas formosae (VU: Vulnerable)

  Family Epialtidae
  Doclea canaliformis (EN: Endangered)
Hyastenus elatus
(EN: Endangered)
Hyastenus subinermis
(EN: Endangered)
Menaethius monoceros
(One-horned spider crab) (VU: Vulnerable)

  Family Eriphiidae
  Eriphia ferox (Red-eyed reef crab) (VU: Vulnerable)

  Family Gecarcinidae
  Discoplax hirtipes (NE: Presumably Nationally Extinct)

  Family Hymenosomatidae
  Crustaenia palawanensis (EN: Endangered)
Elamena globosa (EN: Endangered)

Elamena mendosa (EN: Endangered)
Elamenopsis rotunda (CR: Critically endangered)
Halicarcinus coralicola (VU: Vulnerable)
Neorhunchoplax mangalis (VU: Vulnerable)

  Family Inachidae
  Camposcia retusa (Velcro crab) (VU: Vulnerable)
Paratymolus cygnus (CR: Critically endangered)

  Family Leucosiidae (Pebble crabs)
  Alox somphos (EN: Endangered)
Favus granulatus
(Rubble crab) (EN: Endangered)
Praosia punctata (EN: Endangered)

  Family Majidae (Spider crabs)
  Planotergum mirabile (EN: Endangered)

  Family Ocypodidae (Stalk-eyed crab)
  Dotilla sp. (Soldier crabs)
Dotilla myctiroides (VU: Vulnerable)

Ilyoplax sp. (Semaphore crabs)
Ilyoplax delsmani
(VU: Vulnerable)

Ocypode sp. (Ghost crabs)
Ocypode cordimanus
(VU: Vulnerable)

Uca sp. (Fiddler crabs)
Uca rosea (Rosy fiddler crab) (EN: Endangered)

  Family Parthenopidae (Elbow crabs)
  Aulacolambrus granulosus (CR: Critically endangered)
Cryptopodia fornicata (Domed elbow crab) (EN: Endangered)
Daldorfia horrida (NE: Presumed Nationally Extinct)
Platylambrus echinatus (EN: Endangered)
Pseudolambrus bicornis (Two horned elbow-crab) (CR: Critically endangered)
Rhinolambrus pelagicus (VU: Vulnerable)

  Family Pilumnidae (Hairy crabs)
  Glabropilumnus edamensis (VU: Vulnerable)
Gonatonotus pentagonus (EN: Endangered)
Harrovia albolineata (Feather star crab) (CR: Critically endangered)
Harrovia longipes (Feather star crab) (CR: Critically endangered)
Hypocolpus rugosus (CR: Critically endangered)
Metonia lanka (VU: Vulnerable)
Parapanope euagora (EN: Endangered)
Pilumnus murphyi (VU: Vulnerable)
Pilumnus ohshimai (EN: Endangered)
Retelumnus labyrinthicus (VU: Vulnerable)
Rhizopoides yangae (EN: Endangered)
Zebrida adamsi (EN: Endangered)

  Family Portunidae (Swimming crabs)
  Lucocyclus rotundatus (NE: Presumed Nationally Extinct)

  Family Sesarminidae
  Geosesarma nemesis (EN: Endangered)
Geosesarma peraccae (VU: Vulnerable)
Haberma nanum (VU: Vulnerable)
Sarmatium germaini (Mound crab) (EN: Endangered)
Sesarmoides borneensis (EN: Endangered)

  Family Trapeziidae
  Trapezia cymodoce (Lilac coral crab) (VU: Vulnerable)

  Family Tetraliidae
  Tetralia nigrolineata (Face banded Acropora crab) (CR: Critically endangered)

  Family Xanthidae (Xanthid crabs)
  Atergatis floridus (Floral egg crab) (VU: Vulnerable)
Atergatis integerrimus (Red egg crab) (VU: Vulnerable)
Lophozozymus pictor (Mosaic reef crab) (EN: Endangered)
Banareia subglobosa (EN: Endangered)
Cymo andreossyi (Hairy coral crab) (VU:Vulnerable)
Neoxanthops lineatus (EN: Endangered)
Novactaea bella (EN: Endangered)
Palapedia valentini (VU: Vulnerable)
Platypodia granulosa (Curry Puff reef crab) (EN: Endangered)
Zalasius horii (Paddington Bear crab) (CR: Critcially Endangered)

True crabs (Freshwater)

  Family Potamidae
  Johora singaporensis (EN: Endangered)

  Family Parathelphusidae
  Irmengardia johnsoni (Johnson's freshwater crab) (EN: Endangered)
Parathelphusa reticulata (Swamp forest crab) (EN: Endangered)

Prawns and shrimps see list on the group page

Hermit crabs

  Family Coenobitidae
  Coenobita sp. (Land hermit crab)
Coenobita cavipes (VU: Vulnerable)
Coenobita violascens (VU: Vulnerable)

  Family Porcellanidae (Porcelain crabs)
  Eulenaios cometes (EN: Endangered)
Porcellanella picta (Painted porcelain crab) (VU: Vulnerable)
Pseudoporcellanella monoliensis (False porcelain crab) (VU: Vulnerable)
Raphidopus ciliatus (VU: Vulnerable)

Lobsters and lobster-like animals

  Family Thalassinidae
  Thalassina sp. (Mud lobsters)
Thalassina anomala
(EN: Endangered)
Thalassina gracilis (EN: Endangered)

  Family Upogebiidae
  Wolffogebia phukentensis (EN: Endangered)

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