90
destruction in hard parts such as bones, tests, and shells (Meyers 1990; Stewart
1993; Cook et al. 2003), most host responses and disease symptoms (mycoses) that
can develop in animals in response to fungal infections occur in the soft parts of the
body, in non-mineralized tissues that are readily degraded by bacteria and other
microorganisms. Because soft tissue preservation in animals is exceedingly rare in
the fossil record (Allison and Briggs 1993), there is only a narrow chance for finding fossil evidence of fungal parasitism and pathogenicity in animals.
3.3.4.1 Rhynie Chert
Although the documented record of animals from the Rhynie chert is quite extensive and diverse (e.g., Anderson and Trewin 2003; Dunlop and Garwood 2017),
there is only a single report to date of an ostensible interaction of fungi with animals. The co-occurrence of a chytrid-like organism, Cultoraquaticus trewinii, with
peculiar spherules interpreted as resting eggs of the branchiopod crustacean
Lepidocaris rhyniensis, is purported to represent compelling evidence of a role for
chytrids in a mycoloop (Kagami et al. 2014) that transferred nutrients obtained from
a substrate to the crustacean (Strullu-Derrien et al. 2016). The spherules, which are
of varying diameters and bear spines of varying lengths (Strullu-Derrien et al. 2016:
fig. 4D, E, G, H, J, K), are compared to the resting eggs of the modern Linderiella
santarosae (Anostraca) (Thiéry and Fugate 1994).
3.3.4.2 Amber Inclusions
Specimens enshrined in amber dominate the fossil record of parasitic and pathogenic fungi on insect hosts (Boucot and Poinar 2010). One report describes
Paleocadus burmiticus, a member of the Eccrinales, which were previously thought
to be zygomycetous fungi but are today considered members of the Mesomycetozoea
(Opisthokonta), producing two types of sporangiospores on different thalli that protrude from a primitive wasp preserved in Cretaceous amber from Myanmar (Poinar
2016a). Present-day Eccrinales do not infect members of the Hymenoptera, suggesting a wider host range during the Mesozoic. Geologically younger (Eocene)
Baltic amber has also yielded exquisite examples of insect colonization by fungi,
including a springtail overgrown by conidiophores of the fossil fungus Aspergillus
collembolorum (Fig. 3.4k) (Dörfelt and Schmidt 2005). The authors suggest that
A. collembolorum was a facultative parasite because modern Aspergillus species
usually are facultative parasites or saprotrophs. Another example of fossil Aspergillus
comes from Dominican amber and occurs in the form of well-preserved tufts of
catenulate chains of conidia covering the surface of the abdomen of a fly (Thomas
and Poinar 1988). Although the authors do not comment on the nutritional mode of
the fungus, it is likely that, similar to A. collembolorum, it was a facultative parasite.
Another example of fungal parasitism of animals in Dominican amber is a winged
termite covered by an entomophthoralean fungus (Poinar and Thomas 1982). The
C. J. Harper and M. Krings
destruction in hard parts such as bones, tests, and shells (Meyers 1990; Stewart
1993; Cook et al. 2003), most host responses and disease symptoms (mycoses) that
can develop in animals in response to fungal infections occur in the soft parts of the
body, in non-mineralized tissues that are readily degraded by bacteria and other
microorganisms. Because soft tissue preservation in animals is exceedingly rare in
the fossil record (Allison and Briggs 1993), there is only a narrow chance for finding fossil evidence of fungal parasitism and pathogenicity in animals.
3.3.4.1 Rhynie Chert
Although the documented record of animals from the Rhynie chert is quite extensive and diverse (e.g., Anderson and Trewin 2003; Dunlop and Garwood 2017),
there is only a single report to date of an ostensible interaction of fungi with animals. The co-occurrence of a chytrid-like organism, Cultoraquaticus trewinii, with
peculiar spherules interpreted as resting eggs of the branchiopod crustacean
Lepidocaris rhyniensis, is purported to represent compelling evidence of a role for
chytrids in a mycoloop (Kagami et al. 2014) that transferred nutrients obtained from
a substrate to the crustacean (Strullu-Derrien et al. 2016). The spherules, which are
of varying diameters and bear spines of varying lengths (Strullu-Derrien et al. 2016:
fig. 4D, E, G, H, J, K), are compared to the resting eggs of the modern Linderiella
santarosae (Anostraca) (Thiéry and Fugate 1994).
3.3.4.2 Amber Inclusions
Specimens enshrined in amber dominate the fossil record of parasitic and pathogenic fungi on insect hosts (Boucot and Poinar 2010). One report describes
Paleocadus burmiticus, a member of the Eccrinales, which were previously thought
to be zygomycetous fungi but are today considered members of the Mesomycetozoea
(Opisthokonta), producing two types of sporangiospores on different thalli that protrude from a primitive wasp preserved in Cretaceous amber from Myanmar (Poinar
2016a). Present-day Eccrinales do not infect members of the Hymenoptera, suggesting a wider host range during the Mesozoic. Geologically younger (Eocene)
Baltic amber has also yielded exquisite examples of insect colonization by fungi,
including a springtail overgrown by conidiophores of the fossil fungus Aspergillus
collembolorum (Fig. 3.4k) (Dörfelt and Schmidt 2005). The authors suggest that
A. collembolorum was a facultative parasite because modern Aspergillus species
usually are facultative parasites or saprotrophs. Another example of fossil Aspergillus
comes from Dominican amber and occurs in the form of well-preserved tufts of
catenulate chains of conidia covering the surface of the abdomen of a fly (Thomas
and Poinar 1988). Although the authors do not comment on the nutritional mode of
the fungus, it is likely that, similar to A. collembolorum, it was a facultative parasite.
Another example of fungal parasitism of animals in Dominican amber is a winged
termite covered by an entomophthoralean fungus (Poinar and Thomas 1982). The
C. J. Harper and M. Krings