Notes on High Numbers of Pearls and Blister Pearls from Perna viridis and Preliminary Survey of Bivalve-inhabiting Hydroids in the Eastern Coasts of the Gulf of Thailand

Abstract

On December 23 and 24, 2004, a biological survey of bivalve-inhabiting hydrozoans and pearls was conducted on 398 specimens of five bivalve species (158 specimens of Perna viridis, 148 0f Saccostrea forskali, 81 Meretrix meretrix, 39 M. lyrata and 72 Tegillarca granosa), all obtained in a field and a seafood market in the eastern coasts of the Gulf of Thailand. High number of pearls (31 and 26) embedded in the mantle were detected in two specimens of Perna viridis. Furthermore, many blister pearls (attached pearl) were produced on the inner surface of these shells. However, bivalve-inhabiting hydroids were not yet found in the mantle cavity of any bivalve species examined, though other commensal animals such as copepods and turbellanans were found.