7. THE PHYLA NEMERTINEA, ASCHELMINTHES AND ANNELIDA
275
involved in blister-formation have been reported by Whitelegge (1890),
Kavanagh (1940) and Lunz (1941). In addition, Lankester (1868) has
suggested that the polychaete can secrete a strong acid which accounts
for the tunnels which they burrow in the shell.
Relative to the effects of Polydora on oysters, Whitelegge (1890)
and Roughley (1922, 1925), who worked in Australian waters, have
reported that these polychaete pests can cause heavy mortalities
among oysters. On the other hand, Lunz (1941) and Loosanoff and
Engle (1943), working along the east coast of the United States, have
reported that even heavy infestations do not affect the growth or
health of oysters, although severe shell markings, abnormal appearance
of the mantle, and occasional damage to the adductor muscle may
occur (Mackin and Cauthron, 1952). These apparently opposing viewpoints may well reflect species differences. Whitelegge and Roughley
studied P. ciliata although Wilson (1928) has pointed out that the
polychaetes examined by Whitelegge may be P. ligni. Loosanoff and
Engle studied P. websteri. On the other hand, Korringa (1951a) has
reported that P. ciliata does not inflict serious injuries on Ostrea edulis
in Dutch waters and is of the opinion that the injurious species are
P. websteri and P. hoplura. Obviously then, the effect of Polydora on
oysters is still in need of further investigation.
The species of polychaetes known to be associated with the shell
of commercially important molluscs are listed in Table XV.
275
involved in blister-formation have been reported by Whitelegge (1890),
Kavanagh (1940) and Lunz (1941). In addition, Lankester (1868) has
suggested that the polychaete can secrete a strong acid which accounts
for the tunnels which they burrow in the shell.
Relative to the effects of Polydora on oysters, Whitelegge (1890)
and Roughley (1922, 1925), who worked in Australian waters, have
reported that these polychaete pests can cause heavy mortalities
among oysters. On the other hand, Lunz (1941) and Loosanoff and
Engle (1943), working along the east coast of the United States, have
reported that even heavy infestations do not affect the growth or
health of oysters, although severe shell markings, abnormal appearance
of the mantle, and occasional damage to the adductor muscle may
occur (Mackin and Cauthron, 1952). These apparently opposing viewpoints may well reflect species differences. Whitelegge and Roughley
studied P. ciliata although Wilson (1928) has pointed out that the
polychaetes examined by Whitelegge may be P. ligni. Loosanoff and
Engle studied P. websteri. On the other hand, Korringa (1951a) has
reported that P. ciliata does not inflict serious injuries on Ostrea edulis
in Dutch waters and is of the opinion that the injurious species are
P. websteri and P. hoplura. Obviously then, the effect of Polydora on
oysters is still in need of further investigation.
The species of polychaetes known to be associated with the shell
of commercially important molluscs are listed in Table XV.