32
Asian and Australian aquaculture, i.e., Polydora brevipalpa , P. uncinata ,
P. haswelli , and P. aura , are described here. The shell-associated polydorids that have been reported from these areas were summarized and
reviewed at the same time.
1
Introduction
Spionid polychaetes are distributed in a wide variety of habitats from shallow water to deepwater
depths in all oceans. They are commonly the most
abundant polychaete groups in terms of biomass
and number of species in the coastal benthic environment. Species of Polydora and related genera
(Polychaeta, Spionidae) are the so-called polydorids, and they are found in a wide variety of
substrata, ranging from soft mud to hard calcareous materials (Blake 1996 ; Sato-Okoshi 1999 ,
2000 ). Polydorids are well known for their ability
to bore into various calcareous substrates, e.g.,
coralline algae, corals, and mollusk shells (Blake
and Evans 1973 ; Blake 1996 ; Sato-Okoshi 1999 ).
Although they excavate their burrows for use as a
habitat, some species have been frequently
reported as harmful invaders from the viewpoint
of aquaculture, as they often damage the commercially important mollusk shells by inducing
abnormal shell formation, decreasing their commercial value, reducing their growth rate and
meat yield, and causing heavy mortality (SatoOkoshi et al. 1990 , 2008 ; Okoshi and Sato- Okoshi
1996 ; Handley and Bergquist 1997 ; Mortensen
et al. 2000 ; Lleonart et al. 2003 ; Simon et al.
2006 ). In recent years, the heavily infested abalone shells were observed to be dead in tank-cultured system and it was forced to stop cultivating
in several prefectures in Japan (personal communication). Measures of preventing or controlling
polydorid infestation in commercially important
mollusk shells have been suggested (Handley and
Bergquist 1997 ; Diggles et al. 2002 ; Simon et al.
2010 ), but the problem remains unresolved.
An expansion of molluscan aquaculture has
resulted in a global distribution of certain commercially important mollusk shells (Cohen
and Carlton 1998 ). Consequently, the polydorid
species that associate with these mollusk shells,
such as borers and crevice inhabitants, have also
spread by accompanying commercially important host shells (Bailey-Brock 2000 ; Radashevsky
and Olivares 2005 ; Simon et al. 2006 ). Those
species are not only a source of concern economically (Radashevsky and Olivares 2005 ; Simon
et al. 2006 ) but also pose a threat ecologically
(Cohen and Carlton 1998 ). Ecological disturbances caused by invasive organisms (including
polychaetes) associated with these mollusks are
currently seen as a major cause of diversity loss
worldwide (Mack et al. 2000 ; Miura 2007 ).
The polydorids include several species groups
that are morphologically indistinguishable, with
an insuffi cient number of distinct characters to
enable species level identifi cation (Radashevsky
and Pankova 2006 ; Sato-Okoshi and Abe 2013 ).
At the same time, some species possess a high
degree of intraspecifi c variation, particularly
with respect to pigmentation patterns (SatoOkoshi and Abe 2013 ; Teramoto et al. 2013 ).
Recently, molecular sequence analyses were conducted in some shell-associated Polydora species
(Sato- Okoshi and Abe 2012 , 2013 ; Teramoto
et al. 2013 ), and the results demonstrated that the
nuclear 18S rRNA gene analysis would be an
effective and useful tool to accurately discriminate between these problematic species.
The present study fi rst summarizes the polydorid species to understand the background of the
relevant species associated with commercially
important mollusk shells in East Asia and Australia.
Secondly, the study focuses on harmful Polydora
species known to be responsible for heavy host
shell damage and with the potential to become an
invasive species as a result of accidental transport
on host shells. Morphological, ecological, and
molecular biological characteristics of these
high-risk Polydora species are described here in
order to better trace and monitor the threat they
pose to mollusk fi sheries and ocean ecologies.
W. Sato-Okoshi et al.
Asian and Australian aquaculture, i.e., Polydora brevipalpa , P. uncinata ,
P. haswelli , and P. aura , are described here. The shell-associated polydorids that have been reported from these areas were summarized and
reviewed at the same time.
1
Introduction
Spionid polychaetes are distributed in a wide variety of habitats from shallow water to deepwater
depths in all oceans. They are commonly the most
abundant polychaete groups in terms of biomass
and number of species in the coastal benthic environment. Species of Polydora and related genera
(Polychaeta, Spionidae) are the so-called polydorids, and they are found in a wide variety of
substrata, ranging from soft mud to hard calcareous materials (Blake 1996 ; Sato-Okoshi 1999 ,
2000 ). Polydorids are well known for their ability
to bore into various calcareous substrates, e.g.,
coralline algae, corals, and mollusk shells (Blake
and Evans 1973 ; Blake 1996 ; Sato-Okoshi 1999 ).
Although they excavate their burrows for use as a
habitat, some species have been frequently
reported as harmful invaders from the viewpoint
of aquaculture, as they often damage the commercially important mollusk shells by inducing
abnormal shell formation, decreasing their commercial value, reducing their growth rate and
meat yield, and causing heavy mortality (SatoOkoshi et al. 1990 , 2008 ; Okoshi and Sato- Okoshi
1996 ; Handley and Bergquist 1997 ; Mortensen
et al. 2000 ; Lleonart et al. 2003 ; Simon et al.
2006 ). In recent years, the heavily infested abalone shells were observed to be dead in tank-cultured system and it was forced to stop cultivating
in several prefectures in Japan (personal communication). Measures of preventing or controlling
polydorid infestation in commercially important
mollusk shells have been suggested (Handley and
Bergquist 1997 ; Diggles et al. 2002 ; Simon et al.
2010 ), but the problem remains unresolved.
An expansion of molluscan aquaculture has
resulted in a global distribution of certain commercially important mollusk shells (Cohen
and Carlton 1998 ). Consequently, the polydorid
species that associate with these mollusk shells,
such as borers and crevice inhabitants, have also
spread by accompanying commercially important host shells (Bailey-Brock 2000 ; Radashevsky
and Olivares 2005 ; Simon et al. 2006 ). Those
species are not only a source of concern economically (Radashevsky and Olivares 2005 ; Simon
et al. 2006 ) but also pose a threat ecologically
(Cohen and Carlton 1998 ). Ecological disturbances caused by invasive organisms (including
polychaetes) associated with these mollusks are
currently seen as a major cause of diversity loss
worldwide (Mack et al. 2000 ; Miura 2007 ).
The polydorids include several species groups
that are morphologically indistinguishable, with
an insuffi cient number of distinct characters to
enable species level identifi cation (Radashevsky
and Pankova 2006 ; Sato-Okoshi and Abe 2013 ).
At the same time, some species possess a high
degree of intraspecifi c variation, particularly
with respect to pigmentation patterns (SatoOkoshi and Abe 2013 ; Teramoto et al. 2013 ).
Recently, molecular sequence analyses were conducted in some shell-associated Polydora species
(Sato- Okoshi and Abe 2012 , 2013 ; Teramoto
et al. 2013 ), and the results demonstrated that the
nuclear 18S rRNA gene analysis would be an
effective and useful tool to accurately discriminate between these problematic species.
The present study fi rst summarizes the polydorid species to understand the background of the
relevant species associated with commercially
important mollusk shells in East Asia and Australia.
Secondly, the study focuses on harmful Polydora
species known to be responsible for heavy host
shell damage and with the potential to become an
invasive species as a result of accidental transport
on host shells. Morphological, ecological, and
molecular biological characteristics of these
high-risk Polydora species are described here in
order to better trace and monitor the threat they
pose to mollusk fi sheries and ocean ecologies.
W. Sato-Okoshi et al.