An investigation was made on infestation of the shells of 119 abalone Haliotis diversicolor aquatilis from southern Japan, with burrowing polychaetes Polychaetes Polydora by direct microscopic and soft X-ray radiographic means.
The total 698 specimens of Polydora were collected from the shells of abalone, and the relative number of these worms was 64.5% of P. armata, 25.6% of P. websteri, 9.0% of P. flava orientalis and 0.8% of P. ciliata. The frequency of occurrence of Polydora in the shells of abalone was 33.6% of P. websteri, 14.8% of P. flava orientalis, 5.9% of P. armata and 2.5% of P. ciliata.
Specimens of Polydora were obtained from the shells over 29mm in length, and the borers increased in number with the size of shells. The data indicated that the flesh weight of abalone decreased significantly by the infestation with more than ten individuals of Polydora per shell.