Larval settlement and metamorphosis of the pearl oyster Pinctada fucata in response to biofilms

Biofilms is an important mediator of larval settlement and metamorphosis for the pearl oyster Pinctada fucata, which is an important aquaculture species in South China. However, the role of biofilms in larval settlement and metamorphosis in this species remains unclear. This paper presents the first laboratory study investigating larval settlement and metamorphosis of P. fucata in response to natural biofilms of different ages and biofilm-conditioned seawater. Natural biofilms from 1 to 9 day-old except 6-day-old significantly induced larval settlement, while there was no obvious positive correlation between microbial abundance of the biofilms and percentages of larval settlement and metamorphosis. These results indicate that the inductive effect may be closely associated with biofilms community structure and extracellular products in the biofilms rather than microbial abundance. No inductive effects were observed when larvae were exposed to biofilm-conditioned seawater. Thus, the inductive cues from the natural biofilms seem to result from its surface-associated characteristic rather than waterborne. In addition, this study also provides valuable information for studies of mechanism of larval settlement and metamorphosis in this species, which is useful information for the hatchery industry of this pearl oyster.