although this paucity of collections does not
mean that they are rare in such habitats. Ento-
mopathogenic entomophthoraleans are easily
seen and collected, and they are much more
widely collected and described worldwide than
the “nonentomogenous taxa (Tucker 1981 )
whose microscopic hosts occur in litter or soil
habitats....”
Entomophthoralean asexual spores differ
markedly from those of other zygomycotan
fungi in that they are true conidia (not spor-
angiospores!) formed by blastosporogenesis,
are forcibly discharged in all genera, except
Massospora, and tend strongly to form a vari-
ety of secondary conidia.Ultrastructural con-
firmation of the conidial nature of these spores
is available for taxa in several families of this
order (Dykstra 1994 ; Eilenberg et al. 1986 , 1995 ;
Latge ́ et al. 1989 ). Ultrastructural studies of
some taxa in Zoopagales demonstrate that
their spores also are conidia (Saikawa2011b;
Saikawa and Katsurashima 1993 ; Saikawa and
Sato 1991 ). Entomophthoralean fungi actively
discharge their conidia [Fig.8.1(5–8)] using
several diverse mechanisms (Humber 1989 ).
Turgid cells round off in most genera to cause
the sudden eversion of a papilla (Couch 1939 ).
The conidia ofEntomophthoraspp. discharge
in a cannonlike manner when the conidiogen-
ous cell apex ruptures, although Eilenberg et al.
( 1986 ) proposed an alternative explanation of
this discharge mechanism.Massosporais the
only genus that forms conidia that are passively
rather than actively dispersed.
Nearly all genera of the order Ento-
mophthorales s.s. sensu Humber (2012b), Ento-
mophthoromycetes, form one or more types of
secondary conidia when the primary conidia
land on nonnutritive or other unsuitable sub-
strates. Secondary conidia can be the major
infective units for some of the entomopatho-
genic taxa (e.g.,Entomophthoraspp.). Humber
( 1981 ), King and Humber ( 1981 ), and Ben-
Ze’ev and Kenneth ( 1982 ) discuss the types of
secondary conidia formed; these include one or
more forcibly discharged secondary conidia or
passively dispersed conidia at the apex of long,
capillarylike secondary conidiophores.
Resting spores [Fig. 8.1(13, 14)], zygos-
pores, and azygospores are thick-walled and
form between conjugating cells (gametangia)
of different or the same hyphae or hyphal bod-
ies; they are considered zygospores. Spores
formed without prior gametangial conjugations
of hyphae or hyphal bodies are azygospores.
Evidence suggests that karyogamy and meiosis,
if they occur in a species, take place in the
resting spores regardless of their zygosporic
or azygosporic origins (McCabe et al. 1984 ).
Illustrations of the characters used in the iden-
tification of the entomophthoralean fungi can
be found in Thaxter ( 1888 ), Balazy ( 1993 ),
Humber (1997a), Keller and Petrini ( 2005 ),
and Gryganskyi et al. ( 2012 , 2013 ).c) Neozygitomycetes and Neozygitales
The members of Neozygitomycetes (Humber
2012b) produce hyphal bodies that contain 3–
5, usually four, nuclei in the vegetative cells.
The conidiophore is not branched, a single
conidium is produced, and the primary coni-
dia are subglobose to broadly ovoid and have a
short basal papillum. Conidial discharge is
active by means of papillar eversion, and sec-
ondary conidia are rapidly produced. Each
resting spore is produced on a relatively
short conjugation bridge that arises from the
gametangia that are rounded hyphal bodies.
All portions of Neozygitomycetes possess mel-
anin pigments; the conidia are smoky gray,
and the resting spores are dark gray to black.
The formation of melanized structures is a
cardinal feature of Neozygitomycetes. The
members of Neozygitomycetes were not pro-
posed based on molecular evidence but because
of the production of pigmentation.D. Nonentomophthoralean Subphyla
(Kickxellomycotina, Mortierellomycotina,
Mucoromycotina, Zoopagomycotina)Asexual reproduction in all zygomycete orders
is by nonmotile, single-celled endospores
formed as conidia or in sporangia, sporangiola,
or merosporangia, and by the formation of
chlamydospores, arthrospores, or yeast cells
(Benjamin 1979 ) (Figs.8.2,8.3,8.4, and8.5).224 G.L. Benny et al.