The world’s biggest bivalves are the aptly named giant clams. Inhabiting the warm waters of the Indo-Pacific, the largest of these species, the eponymous giant clam (Tridacna squamosal), can reach up to 1.2 meters (4 feet) in length and wiegh over 230 kilograms (500 pounds). Historically known as the killer clam for its supposed ability to trap careless divers, these harmless and colorful bivalves are favorite animals for divers and snorkelers to spot, but they may also be big players in the ecosystem.
The world’s biggest bivalves are the aptly named giant clams. Inhabiting the warm waters of the Indo-Pacific, the largest of these species, the eponymous giant clam (Tridacna squamosal), can reach up to 1.2 meters (4 feet) in length and wiegh over 230 kilograms (500 pounds). Historically known as the killer clam for its supposed ability to trap careless divers, these harmless and colorful bivalves are favorite animals for divers and snorkelers to spot, but they may also be big players in the ecosystem.
Giant clams, regardless of species, are among the most immediately recognizable animals on coral reefs, yet their ecological roles in these complex ecosystems have not been studied in depth. Realizing this, both Mei Lin Neo and Peter Todd of the National University of Singapore recently released a paper to bridge the gap.
Trawling through nearly 500 published papers covering over ten years’ worth of research, their study is the first to quantify and highlight the many roles of this charismatic marine animal.
From reef backbone to food
All organisms contribute differently to their ecosystems from birth to death, and it is no different for the giant clam. Young clams grow quickly compared to corals, the other primary producers of a reef. Depending on clam and coral species, this rate can range from twice to 75 times as quickly as corals. In the Tatakoto Atoll of French Polynesia alone the population of small giant clams (Tridacna maxima) is capable of producing an astounding 238 kilograms of dry weight per hectare per year (212lbs/ac/yr) of biomass.
Of course, many of these young clams fall prey to predation. At least 75 animals are known to rely on these bivalves as a food source, whether as recently-released gametes (sperm and eggs) or as juveniles. Even fish occasionally nip chunks off the mantles of adult clams, though the giant clams' expulsions of zooxanthellae and nutrient-rich feces likely make more significant dietary contributions to reef fish.
However, giant clams also serve as shelters for a wide range of animals. Dense aggregations of the bivalves are fish nurseries while the shells themselves are home to many different encrusting and burrowing reef animals. On the shells of just eight fluted giant clam (Tridacna squamosal) individuals in Singapore, researchers found at least 49 species of organisms.
Unfortunately, there is no data yet that shows how effective giant clams are as surfaces compared to other reef creatures such as corals.
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Giant clam image via Shutterstock.
