Differential community development of fouling species on the pearl oysters Pinctada fucata, Pteria penguin and Pteria chinensis (Bivalvia, Pteriidae).

A field experiment documented the development of fouling communities on two shell regions, the lip and hinge, of the pearl oyster species Pinctada fucata, Pteria penguin and Pteria chinensis. Fouling communities on the three species were not distinct throughout the experiment. However, when each species was analysed separately, fouling communities on the lip and hinge of P. penguin and P. chinensis were significantly different during the whole sampling period and after 12 weeks, respectively, whereas no significant differences could be detected for P. fucata. There was no significant difference in total fouling cover between shell regions of P. fucata and P. chinensis after 16 weeks; however, the hinge of P. penguin was significantly more fouled than the lip. The most common fouling species (the hydroid Obelia bidentata, the bryozoan Parasmittina parsevalii, the bivalve Saccostrea glomerata and the ascidian Didemnum sp.) showed species-specific fouling patterns with differential fouling between shell regions for each species. The role of the periostracum in determining the community development of fouling species was investigated by measuring the presence and structure of the periostracum at the lip and hinge of the three pearl oyster species. The periostracum was mainly present at the lip of the pearl oysters, while the periostracum at the hinge was absent and the underlying prismatic layer eroded. The periostracum of P. fucata lacked regular features, whereas the periostracum of P. penguin and P. chinensis consisted of a regular strand-like structure with mean amplitudes of 0.84 microm and 0.65 microm, respectively. Although the nature and distribution of fouling species on the pearl oysters was related to the presence of the periostracum, the periostracum does not offer a fouling-resistant surface for these pearl oyster species.