SQUAMOSE GIANT CLAM (Tridacna squamosa)
Common in shallow reefs around the Similan Islands and Phuket to about 10 m. Embedded hinge-down in corals, shell with rows of flanges.
This species carries both sexes in its body; eggs and sperm get released at different times to avoid self-fertilization.
THORNY OYSTER (Spondylus varius)
This species has a heavy, almost circular shell. One shell is cemented to the substrate, the other shell is moveable as lid.
Both shells have radial ribs and spines on the outer surface. It rapidly closes when shadowed.
Normally heavy overgrown by various invertebrates.
SNAILS & NUDIBRANCHS
The distinct body shape of the shells of this genus is due to the muddy areas on which it lives.
It feeds on mussels, hidden in sand and mud.
These sea slugs are masters of chemical defense: they are capable of polluting an entire aquarium if stressed in any way.
They produce a strong toxin that can kill all life in the aquarium. They have no known enemies.
This large nudibranch is mostly found crawling in pairs.
Each animal alternately raises and lowers its head as it crawls. It feeds on sponges.
MARBLED OCTOPUS (Octopus aegina)
This species can be found down to a depth of at least 40 m duiring dives at the Similan Islands. The nocturnal hunter feeds on crustaceans and shells.
Octopuses have a large brain and are regarded as the most highly developed invertebrates.
PHARAO CUTTLEFISH (Sepia pharaonis)
Mostly nocturnal species. During mating and spawning they can also be seen in daytime.
Cuttlefish are well-known for rapid color changes, when disturbed. They feed on crabs and small fishes.