352
(e.g., Nagler et al. 2017a and references therein). These different strategies seem to
be quite strictly coupled to distinct ingroups:
• Representatives of Cirolanidae typically show a scavenging lifestyle (Bruce 1986).
• Representatives of Corallanidae are scavengers, predators, but some are also
temporary ectoparasites on fishes and zooplankton (Monod 1969; Bruce et al.
1982; Gentil-Vasconcelos and Tavares-Dias 2015).
• Representatives of Aegidae are temporary ectoparasites on fishes: they attach
just shortly for feeding and leave their hosts afterwards (Brusca 1983).
Representatives of Aegidae can be interpreted as “micropredators” sensu Lafferty
and Kuris (2002), but in the framework of understanding the evolution of parasitism, they should be better considered as ‘temporary parasites’, i.e. organisms
that feed on a host without killing it, but interacting with it only for the time of
feeding.
• Immature representatives of Cymothoidae have a lifestyle similar to representatives of Aegidae, attaching just shortly for feeding to their host fishes and thus
can be considered as temporary ectoparasites; adults are obligatory, permanent
ectoparasites on or in their host fishes (Brusca 1981; Bunkley-Williams and
Williams 1998; Smit et al. 2014). One of the best studied cases of the parasitic
strategies of Cymothoidae, and the most popularised one, are probably isopods
that are replacing the tongue of their host fishes and feed in a kleptoparasitic
manner (Brusca and Gilligan 1983; Thatcher 2000; Costa et al. 2010; Hadfield
et al. 2011; Parker and Booth 2013).
• Gnathiidae is not considered as an ingroup of Cymothoida by many authors, yet
their lifestyle and the associated morphology strongly argues for such an ingroup
position (see e.g. Nagler et al. 2017a). During a specific larval phase (praniza
larva), gnathiiids feed similar to representatives of Aegidae and juvenile
Cymothoidae on host fishes, representing temporary ectoparasites; their adults
do not consume food (Smit and Davies 2004; Hispano et al. 2014).
• Representatives of Epicaridea have a specific lifecycle involving also a host
change coupled to their ontogenetic phase. After hatching as epicaridium larva,
they infest intermediate hosts, small crustaceans such as copepods, as microniscus stage. As cryptoniscus larva, they look for and infest their final hosts, decapodan crustacean (Williams and Boyko 2012). Depending on their infection site
and their adult morphology, adult epicarideans can be considered as permanent
ecto-parasites or endo-parasites, with some additionally acting as parasitic castrators (Beck 1980).
The evolution of parasitism within Cymothoida has been proposed to have
occurred stepwise by a shift from non-parasitic to parasitic lifestyles (Fig. 10.1;
Nagler et al. 2017a). Due to their enormous diversity in morphology and ecology,
Cymothoida is an interesting group for studying the evolution of parasitism, especially together with deep-time aspects based on fossils and their diversity and abundance in marine habitats.
J. T. Haug et al.
(e.g., Nagler et al. 2017a and references therein). These different strategies seem to
be quite strictly coupled to distinct ingroups:
• Representatives of Cirolanidae typically show a scavenging lifestyle (Bruce 1986).
• Representatives of Corallanidae are scavengers, predators, but some are also
temporary ectoparasites on fishes and zooplankton (Monod 1969; Bruce et al.
1982; Gentil-Vasconcelos and Tavares-Dias 2015).
• Representatives of Aegidae are temporary ectoparasites on fishes: they attach
just shortly for feeding and leave their hosts afterwards (Brusca 1983).
Representatives of Aegidae can be interpreted as “micropredators” sensu Lafferty
and Kuris (2002), but in the framework of understanding the evolution of parasitism, they should be better considered as ‘temporary parasites’, i.e. organisms
that feed on a host without killing it, but interacting with it only for the time of
feeding.
• Immature representatives of Cymothoidae have a lifestyle similar to representatives of Aegidae, attaching just shortly for feeding to their host fishes and thus
can be considered as temporary ectoparasites; adults are obligatory, permanent
ectoparasites on or in their host fishes (Brusca 1981; Bunkley-Williams and
Williams 1998; Smit et al. 2014). One of the best studied cases of the parasitic
strategies of Cymothoidae, and the most popularised one, are probably isopods
that are replacing the tongue of their host fishes and feed in a kleptoparasitic
manner (Brusca and Gilligan 1983; Thatcher 2000; Costa et al. 2010; Hadfield
et al. 2011; Parker and Booth 2013).
• Gnathiidae is not considered as an ingroup of Cymothoida by many authors, yet
their lifestyle and the associated morphology strongly argues for such an ingroup
position (see e.g. Nagler et al. 2017a). During a specific larval phase (praniza
larva), gnathiiids feed similar to representatives of Aegidae and juvenile
Cymothoidae on host fishes, representing temporary ectoparasites; their adults
do not consume food (Smit and Davies 2004; Hispano et al. 2014).
• Representatives of Epicaridea have a specific lifecycle involving also a host
change coupled to their ontogenetic phase. After hatching as epicaridium larva,
they infest intermediate hosts, small crustaceans such as copepods, as microniscus stage. As cryptoniscus larva, they look for and infest their final hosts, decapodan crustacean (Williams and Boyko 2012). Depending on their infection site
and their adult morphology, adult epicarideans can be considered as permanent
ecto-parasites or endo-parasites, with some additionally acting as parasitic castrators (Beck 1980).
The evolution of parasitism within Cymothoida has been proposed to have
occurred stepwise by a shift from non-parasitic to parasitic lifestyles (Fig. 10.1;
Nagler et al. 2017a). Due to their enormous diversity in morphology and ecology,
Cymothoida is an interesting group for studying the evolution of parasitism, especially together with deep-time aspects based on fossils and their diversity and abundance in marine habitats.
J. T. Haug et al.