Smooth Giant Clam/Southern Giant Clam/Derasa Clam

Smooth Giant Clam/Southern Giant Clam/Derasa Clam Tridacna derasa

Type of Animal:

Outer reefs/reef edges, intertidal coral areas, lagoons, coral outcrops, within Acropora corals, sandy flats, rubble piles, rock faces, found at depths of 1-65 ft

Indo-West Pacific, C Pacific, & S Pacific

Very large clam, smooth shell, lack of scutes (scale-like shell protrusions), colorful mantle has wavy stripe or spot pattern, large plain shell, 2nd largest of the giant clams

Make food for themselves in 4 ways-firstly, they have large amounts of symbiotic single-celled dinoflagellate algae (zooxanthellae) in tissues-due to these clams needing moderately lit to well-lit habitats, algae may make too much food for themselves giving extra carbon/glucose to clam. Secondly, zooxanthellae can be eaten by amoebid cells within host clam. Thirdly, they can absorb nutrients from water. Fourthly, they can act as filter-feeders, straining phytoplankton/zooplankton/detritus/algae w/ gills.

Status in Wild:

Use in aquaculture reducing demand for wild-caught clams

Mostly in colonies of 15-30 clams, though sometimes solitary as well

Additional Info:

Young: Trocophore
Group: Colony/Aggregation/Bed

90-400 lbs

12 hours

Life Span:
30-70 years in captivity, 150-250 years in wild

Adult: 18-23 in
Young: 4 in

Main predators are parasitic/predatory snails, fish, sea snakes, sea stars, crabs, lobsters, shrimp, bristleworms, fireworms, octopus, burrowing sponges, clam worms, & anemones.

Threatened due to aquarium trade, hunting for food, hunting for shells, medicinal use, habitat degradation/destruction, water pollution, & coastal development.

They’re very slow growers after reaching maturity.

Reproduction stimulated by lunar cycle, time of day, & presence of other eggs/sperm.

They detach byssus (tuft of long tough filaments) as they mature.

Most readily available giant clams in aquarium trade.

Mantle colors result of crystalline pigment cells.

Fun Fact(s):
Start life as free-swimming larvae, then developing into new larval stage capable of filter-feeding. Develop feet at 3rd larval stage, allowing it to alternately swim/rest. Become juveniles at around 10 days old, when they acquire zooxanthellae, starting symbiotic relationship. Juveniles become males at 2-3 years old, eventually becoming hermaphroditic once they reach 12 in.

Due to being hermaphrodites much of their life, sperm released 1st followed by eggs, avoiding self-fertilization.

3 thoughts on “Smooth Giant Clam/Southern Giant Clam/Derasa Clam

  1. Dani

    Greetings from Florida! I’m bored at work so I decided
    to browse your website on my iphone during lunch break.
    I enjoy the info you provide here and can’t wait to take a look when I get home.
    I’m surprised at how fast your blog loaded on my cell phone ..
    I’m not even using WIFI, just 3G .. Anyways, wonderful blog!

  2. Kenny

    Hi there would you mind stating which blog platform you’re using?

    I’m planning to start my own blog in the near future
    but I’m having a tough time deciding between BlogEngine/Wordpress/B2evolution and Drupal.
    The reason I ask is because your design seems different then most blogs and I’m looking for
    something completely unique.
    P.S Sorry for getting off-topic but I had to ask!


Leave a Reply

Your email address will not be published. Required fields are marked *