Sunday, October 28, 2012


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: Stuck to rock. With Asian Green Mussels

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

The invasive1 Mytilopsis sallei at Sungei Serangoon ©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. Common Nerite (Nerita articulata) ©Tan KH. 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

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

Atopos sp. at Neo Tiew Lane 2. Yellow-shelled semi-slug (Parmarion sp.) at Dairy Farm ©Tan KH

Common Big-jawed Spider with eggs of the introduced Golden Apple Snail (Pomacea canaliculata) at Springleaf ©Tan KH


1. The invasive Caribbean bivalve Mytilopsis sallei (Dreissenidae) introduced to Singapore and Johor Bahru, Malaysia

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