Amusium pleuronectes
A gliding scallop of the West Pacific, valued for food and aquaculture.
The Asian moon scallop (*Amusium pleuronectes*) is a bivalve mollusk in the scallop family Pectinidae, found in the West Pacific. One extinct subspecies, *A. pleuronectes okinawaensis*, has been described. People eat this scallop across its range, and there have been efforts to farm it.
Its two near-circular shells are nearly symmetrical, unlike those of *Pecten* species. The right (lower) valve is slightly deeper than the left (upper) one. Both valves are very smooth, with visible radial lines and growth marks. The left valve is pinkish-brown, while the right valve is white. Individuals typically reach 8 cm in shell height, with a maximum of 10 cm. The shell has 22 to 34 internal radial ribs; a supposed southern subspecies, *A. pleuronectes australiae*, has fewer ribs (22–24).
This scallop lives on the seafloor at depths of 10 to 160 m, often forming large groups. It is one of the few scallop species that can glide efficiently, swimming more than 5 m per effort. Its flattened valves help it glide during a level swimming phase. Other gliding scallops include members of *Adamussium*, *Placopecten*, and *Ylistrum*. The convergent evolution among these groups is so strong that *Ylistrum* species were once placed in *Amusium*; genetic and rib-pattern analysis later separated them.
As filter feeders, these scallops eat diatoms like *Isochrysis galbana*, *Tetraselmis tetrahele*, and *Chaetoceros* sp. They are protandrous (starting life as males) and reproduce year-round, with a major peak in February and a minor one from July to September. First maturity occurs at about 5.4 cm shell height.
Fisheries target this species; in the northern Philippines, the peak season runs from April to June. The meat is sold fresh at wet markets in places like Malaysia and Indonesia. In Hong Kong, it is dried and used in double-stewed soup. Aquaculture attempts have found that natural spawning in controlled conditions works better than induced spawning.
Quick Facts
- Genus
- Amusium
- Species
- pleuronectes
Facts from the source article.
Lore & Background
The two near-circular valves of Amusium pleuronectes are nearly symmetrical, with the right valve slightly deeper than the left. The left valve is pinkish-brown, while the right valve is white, both bearing radial lines and growth marks. Individuals typically reach 8 cm in shell height, with a maximum of 10 cm. The shell has 22 to 34 internal radial ribs; a supposed southern subspecies, A. pleuronectes australiae, reportedly has 22–24 ribs, fewer than the nominate subspecies.
This species is benthic but is one of the few scallops considered a glider, swimming more than 5 m per effort. Its flattened valves enable a level swimming phase. Convergent evolution with other gliding scallops (Adamussium, Placopecten, Ylistrum) is so extensive that Ylistrum species were once classified under Amusium, only separated by DNA analysis and internal ribbing patterns.
A. pleuronectes is a filter feeder, consuming diatoms such as Isochrysis galbana, Tetraselmis tetrahele, and Chaetoceros sp. It is protandrous and reproduces year-round, with a major peak in February and a minor peak between July and September. First maturity occurs at about 5.4 cm shell height.
Reader's Guide
Amusium pleuronectes is significant as a food species throughout its West Pacific range, sold fresh at wet markets in Malaysia and Indonesia, and dried in Hong Kong for double-stewed soup. Fisheries target it, with peak season in the northern Philippines from April to June. Aquaculture efforts have been attempted, with natural spawning under controlled conditions proving more effective than induced spawning. The species also holds scientific interest due to its gliding locomotion and convergent evolution with other scallop genera, which historically led to taxonomic confusion. Its flattened, symmetrical valves and efficient swimming distinguish it from many other scallops, making it a notable subject for studies of bivalve adaptation and fisheries management.
Did You Know?
- The two valves are differently colored: the left is pinkish-brown and the right is white.
- It is one of the few scallop species that can glide more than 5 m per swimming effort.
- The species is protandrous, meaning it changes sex from male to female as it matures.
- A supposed southern subspecies, A. pleuronectes australiae, has 22–24 internal ribs, fewer than the nominate subspecies.
Frequently Asked Questions
What is Amusium pleuronectes?
It is a bivalve mollusk commonly known as the Asian moon scallop, placed in the scallop family Pectinidae. It is a gliding scallop native to the West Pacific region.
What does Amusium pleuronectes look like?
Its two near-circular shells are nearly symmetrical, with the left (upper) valve showing a pinkish-brown tone and the right (lower) valve appearing white. Both valves are very smooth, displaying visible radial lines and growth marks, and the right valve sits slightly deeper than the left.
Where does Amusium pleuronectes live and how large does it grow?
It inhabits depths ranging from about 10 to 160 meters across the West Pacific. Typical individuals reach roughly 8 cm in shell height, with a maximum of around 10 cm.
Is Amusium pleuronectes eaten or farmed?
Yes, people across its native range consume this scallop as food, and it has also been the target of aquaculture efforts. It is valued both as a wild-caught and cultivated species.
How is Amusium pleuronectes different from other scallops such as Pecten?
Unlike Pecten species, the Asian moon scallop has nearly symmetrical, near-circular shells rather than a strongly fan-shaped profile. It also carries 22 to 34 internal radial ribs, and one extinct subspecies, A. pleuronectes okinawaensis, has been described from its range.
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