cystidia are morphologically and developmen-
tally distinct cell types (Brobyn and Wilding
1977 ) that may occur together or independently
in a species. Rhizoids or cystidia are not formed
by many entomopathogens or, apparently, any
saprobic Entomophthorales.d) Resting Spores
The formation of resting spores [Fig.8.1(12–14)]
in members of Entomophthoromycota, whether
as zygospores or azygospores, is strictly homo-
thallic(Humber 1989 ); no evidence for hetero-
thallism has been found in this order. Research
needstobedonetodistinguishbetweenthe
morphological [zygospores (Fig.8.1(12)) versus
azygospores] and genetic (karyogamic/meiotic
versus apogamic) definitions of sex. While kary-
ogamy and meiosis have never been confirmed
cytologically in zygomycotan fungi, resting
spores in most families of Entomophthoromy-
cota are initially multinucleate and either remain
multinucleate or are reduced to a binucleate state
in fully dormant mature spores; resting spores in
Basidiobolomycetes and Neozygitomycetes are
binucleate at the time of their formation. McCabe
et al. ( 1984 ) regarded binucleate resting spores as
beinglikelytoundergokaryogamyandmeiosis
during germination.- Taxonomy to Classes and Orders
Humber ( 1989 ) published a six-family classifi-
cation of Entomophthoromycota (as Ento-
mopthorales), in which the taxa were
distinguished primarily by nuclear characters
[Fig.8.1(10, 11)] (size, presence, and stainabil-
ity with aceto-orcein or other nuclear stains of
interphasic chromatin in unfixed nuclei, pres-
ence and placement of nucleoli, and mitotic
pattern) and the modes of formation and ger-
mination of resting spores(Humber 1989 ).Balazy ( 1993 ) only recognized five families and
a generic taxonomy closer to that originally
outlined by Batko (1964a,b,c,d).
All genera in Entomophthoraceae(Ento-
mophthoromycetes)and Neozygitaceae(Neo-
zygitomycetes) are obligate pathogens of
insects and allied arthropods; the latter taxa
are also distinguished by pigmentation. The
monotypic family Completoriaceae (Comple-
toria complens Lohde) parasitizes fern
prothallia.Members ofMeristacraceae,distin-
guished by erect conidiophores bearing sev-
eral lateral conidia, parasitize nematodes,
tardigrades, and, in one reported instance,
insects(Couch et al. 1979 ). Two families, Ancy-
listaceae (Entomophthoromycetes) and Basi-
diobolaceae (Basidiobolomycetes), are
primarily saprobic in plant detritus, organic
litter, and the dung of cold-blooded vertebrates.
Ancylistesis obligately parasitic on species of
the desmid algaClosteriumNitzsch ex Ralfs.
BasidiobolusorConidiobolusspecies may be
obligately or facultatively zoophilic (and may
cause mycoses in vertebrates).
Generic characters distinguishing the
genera of Entomophthoromycota include (1)
conidial characters such as shape, nuclear num-
ber, and bi- or unitunicate status (with a sepa-
rable or inseparable outer wall layer,
respectively), and mode of discharge; (2) conid-
iophore characters such as branching (simple,
branched, or an erect multisporic axis); and (3)
general habit and host range(Humber 1981 ,
1989 ,1997a). These primary generic characters
may be augmented with secondary characters,
such as the absence or presence (and morphol-
ogy) of rhizoids and cystidia, types of secondary
conidia produced, morphological characters of
the resting spores, vegetative characters, espe-
cially whether vegetative cells are walled or pro-
toplastic, and pathobiological characters, suchFig. 8.1(continued) central nucleolus. 12. Immature
zygospore ofBasidiobolus ranarumshowing beaklike
projections with remnants of prezygotic mitotic nuclei.
13. Mature resting spore ofTarichiumsp. from tipulid
fly with a dark, roughened outer wall showing clear
fenestra where spore was attached to parental cell dur-
ing development. 14. Mature resting spore, as in 13 ,cracked open to show smooth, uncolored inner wall
layer and projecting cytoplasm, including a stained
nucleus. Scale bars in 1 and 14 are the same size—
bars give magnification for each figure. 1 , 9. Bar
200 mm. 2 .Bars 150 mm. 3 .Bars 75 mm. 4 .Bars 85 mm.
5 , 6 , 8 , 10 , 11 .Bars 50 mm. 7 .Bars 30 mm. 12 , 13 .Bars
70 mm. 14 .Bars 80 mm◂
222 G.L. Benny et al.