Chequered Carpet Shell

• It is told from the introduced Manila clam (Ruditapes philippinarum) by having its two siphons separate right to the base, whereas in the Manila clam they are fused for much of their length.
• It is the native European clam and the most prized in the kitchen; in Spain it is the almeja fina, the one used for almejas a la marinera.
• Its production has been declining for decades for two reasons that go together: the parasite Perkinsus olseni, which causes perkinsosis, and competition from the introduced Manila clam, Ruditapes philippinarum.
• In 2025 its first reference genome was published, assembled to chromosome level, precisely in order to look for the genetic basis of resistance to that parasite.
• It has been proposed as a bioindicator of water quality because of its ecological and economic value.
• It is told apart from the Manila clam by the siphons, separate along their whole length in the chequered carpet shell and fused at the base in the Manila clam.

Skeleton type

Invertebrate - external calcareous bivalve shell (mollusc)

Habitat and environment

Intertidal and subtidal muddy sands of estuaries and rias

Sexual maturity

1 year

Sources consulted: Linneo (1758); Sambade et al. (2025), Evolutionary Applications; Leite et al. (2013), BMC Genomics; FAO; ScienceDirect (Hughes 1989); Science Advances, How colonial animals evolve; Wikipedia, Zooid