156
Boring clams like pholadids can excavate a variety of substrates, including corals
and shells of the other mollusks (Lauckner 1983). For example Diplothyra curta is
known to bore the shells of oysters (Crassostrea virginica; Turner 1954; Galtsoff
1964), while Penitella conradi bores in the shells of both the bivalves and snails
Mytilus californianus, Pododesmus sp., Haliotis spp. and Astraea (Turner 1955). The
mytilid genus Lithophaga contains a variety of species that bore limestone, dead and
living corals, as well as the shells of living mollusks, i.e. oysters (Ogle 1976; Morton
and Scott 1980; Scott 1986; Brickner et al. 1993; Kleemann 1996; Mauna et al. 2005;
Scaps et al. 2008; Bagur et al. 2013). Varying degrees of bivalve specialization to
host species are observed. For example, L. mucronata is host specific to the coral genus
Montipora and L. simplex larval metamorphosis is induced by living corals of only
two species (Astreopora myriophthalma, Goniastrea pectinata)—most commonly
the parent host coral (Morton and Scott 1980; Mokady et al. 1992). These clams burrow in their substrates by chemical means (Morton and Scott 1980). The mytilid
Mytilus edulis was found by Wiborg (1946) according to Lauckner (1983) to have
settled within the mantle cavity of Modiolus modiolus—this location may indicate a
parasitic relationship; however these authors believe it was accidental settlement.
Adult Mytilus edulis were also described as settling on the gills of decapods—Paralithodes camtschaticus and Carcinus meanas (Jansen et al. 1998; Poulter et al. 2018).
Most likely it is a case of accidental colonization, with negative outcomes for the
crab. The bivalves were presumably not feeding directly on their hosts’ tissues, however they may have negatively altered the crabs’ respiratory function (Poulter et al.
2018). Other mytilids, members of the genus Musculus, and a pandorid Mytilimeria
nuttalli often live covered by the tissues of a variety ascidians species (Roberts and
Breen 1985; Cañete and Rocha 2013). The pteriid Vulsella vulsella is an obligate
sponge dwelling bivalve within the order Ostreida, however it is interpreted as a case
of a filtering-mutualism, not a parasitic relation (Tsubaki and Kato 2014). The hiatellid Hiatella arctica was also described as an epibiont in the branchial chamber of
Chionoecetes bairdi and (together with M. edulis, M. trossulus and pectinid
Heteranomia scuamula) from the carapax surface of Lithodes maia, Paralithodes
camtschaticus and Hemigrapsus sanguineus crabs (Dick et al. 1998; Jansen et al.
1998; Isaeva et al. 2001; Dvoretsky and Dvoretsky 2008) with no preferred surface
for settlement (live or dead) thus might be best interpreted as accidental associates.
5.1.2 Galeommatoidea
Galeommatoidea (= Erycinacea, = Leptonacea) bivalves are a diverse group of
marine, globally distributed, small-bodied bivalves (often less than 1 cm), known
since the Cretaceous and living in shallow-water environments (Li et al. 2012,
2016). Some species are free-living, typically restricted to hard bottom environments (Wear 1966; Booth 1979; Chanley and Chanley 2010; Li et al. 2012; Bhaduri
et al. 2017), while most species have been reported from soft sediments, living their
lives as commensals or even parasites of other benthic organisms (Appukuttan
A. Skawina
Boring clams like pholadids can excavate a variety of substrates, including corals
and shells of the other mollusks (Lauckner 1983). For example Diplothyra curta is
known to bore the shells of oysters (Crassostrea virginica; Turner 1954; Galtsoff
1964), while Penitella conradi bores in the shells of both the bivalves and snails
Mytilus californianus, Pododesmus sp., Haliotis spp. and Astraea (Turner 1955). The
mytilid genus Lithophaga contains a variety of species that bore limestone, dead and
living corals, as well as the shells of living mollusks, i.e. oysters (Ogle 1976; Morton
and Scott 1980; Scott 1986; Brickner et al. 1993; Kleemann 1996; Mauna et al. 2005;
Scaps et al. 2008; Bagur et al. 2013). Varying degrees of bivalve specialization to
host species are observed. For example, L. mucronata is host specific to the coral genus
Montipora and L. simplex larval metamorphosis is induced by living corals of only
two species (Astreopora myriophthalma, Goniastrea pectinata)—most commonly
the parent host coral (Morton and Scott 1980; Mokady et al. 1992). These clams burrow in their substrates by chemical means (Morton and Scott 1980). The mytilid
Mytilus edulis was found by Wiborg (1946) according to Lauckner (1983) to have
settled within the mantle cavity of Modiolus modiolus—this location may indicate a
parasitic relationship; however these authors believe it was accidental settlement.
Adult Mytilus edulis were also described as settling on the gills of decapods—Paralithodes camtschaticus and Carcinus meanas (Jansen et al. 1998; Poulter et al. 2018).
Most likely it is a case of accidental colonization, with negative outcomes for the
crab. The bivalves were presumably not feeding directly on their hosts’ tissues, however they may have negatively altered the crabs’ respiratory function (Poulter et al.
2018). Other mytilids, members of the genus Musculus, and a pandorid Mytilimeria
nuttalli often live covered by the tissues of a variety ascidians species (Roberts and
Breen 1985; Cañete and Rocha 2013). The pteriid Vulsella vulsella is an obligate
sponge dwelling bivalve within the order Ostreida, however it is interpreted as a case
of a filtering-mutualism, not a parasitic relation (Tsubaki and Kato 2014). The hiatellid Hiatella arctica was also described as an epibiont in the branchial chamber of
Chionoecetes bairdi and (together with M. edulis, M. trossulus and pectinid
Heteranomia scuamula) from the carapax surface of Lithodes maia, Paralithodes
camtschaticus and Hemigrapsus sanguineus crabs (Dick et al. 1998; Jansen et al.
1998; Isaeva et al. 2001; Dvoretsky and Dvoretsky 2008) with no preferred surface
for settlement (live or dead) thus might be best interpreted as accidental associates.
5.1.2 Galeommatoidea
Galeommatoidea (= Erycinacea, = Leptonacea) bivalves are a diverse group of
marine, globally distributed, small-bodied bivalves (often less than 1 cm), known
since the Cretaceous and living in shallow-water environments (Li et al. 2012,
2016). Some species are free-living, typically restricted to hard bottom environments (Wear 1966; Booth 1979; Chanley and Chanley 2010; Li et al. 2012; Bhaduri
et al. 2017), while most species have been reported from soft sediments, living their
lives as commensals or even parasites of other benthic organisms (Appukuttan
A. Skawina