Mortierellales and Mucorales. Several species
ofMortierellawere screened and compared
with members of Mucorales for the formation
of trisporic acid and its precursors. The gene
(TSP1) for 4-dihydromethyltrisporate dehy-
drogenase was found in Mortierella and
selected members of Mucorales and may
occur in other zygomycotan fungi (Schimek
et al. 2003 ).
Werkman ( 1976 ) studied mating inZygor-
hynchus moelleriVuill., a homothallic member
of Mucorales. The minus () gametangium is a
cell on the main sporangiophore and becomes
the smaller of the two suspensors, whereas the
other gametangium is plus (+); it is borne on a
side branch and at maturity is the larger of the
two suspensors.
Schimek and Wo ̈stemeyer ( 2006 , 2009 )
and Wo ̈stemeyer and Schimek ( 2007 )reviewed
the chemical pathway for the production of
trisporic acid and its precursors in three het-
erothallic members of Mucorales,B. trispora,
Mucor mucedoFresen., andPhycomyces blake-
sleeanus, in which the process has been stud-
ied. Feofilova ( 2006 ) discussed heterothallism
and its application in industry for the
increased production ofb-carotene, lycopene,
sterols, and other isoprenoids by mated cul-
tures ofB. trispora.
Parasitella parasitica (Bainier) Syd. is a
biotrophic, gall-forming parasite of other
Mucorales members. This species induces
hosts to produce galls (Thaxter 1895 , Plate
XXXIV, Figs. 10–13) or sikyotic cells that
mature to form sikyospores.P. parasitica is
heterothallic, and parasitism occurs only on a
host of the opposite mating type. Absidia
glaucaHagem is the host used in mating stud-
ies. Zygospores are formed byP. parasiticaonly
if one of the mating types is parasitizing a host.
Trisporic acid is involved in host–parasite rec-
ognition (Wo ̈stemeyer et al. 1995 ).
IV. Development of Taxonomic Theory
Many taxa of Mucorales s.l. were described by
the mid-nineteenth century. Van Tieghem
( 1878 ) published the first classification of
Mucorales. Thaxter’s ( 1888 ) monograph of
Entomophthoreae (Entomophthorales) formed
the basis for many, especially early, treatments
of the group (Waterhouse 1973 ). A very distinct
and nearly equally influential approach to ento-
mophthoralean taxonomy was developed even
earlier in Europe (Brefeld 1870 ; Nowakowski
1883 ). The earliest molecular studies on the
phylogeny of Entomophthorales (Jensen et al.
1998 ; Nagahama et al. 1995 ) suggested that
these fungi were readily distinguished from
other zygomycetes.
Fungi in Entomophthorales were not
included in van Tieghem’s ( 1878 ) concept of
Mucorales, a scheme followed by most students
of zygomycetes (Benjamin 1979 ). Many early
students of Mucorales placed considerable
emphasis on the production of unispored spor-
angiola, or so-called conidial fungi in their
opinion (Benny and Benjamin 1975 ). Thaxter
( 1922 ) monographed the sporocarpic Endogo-
naeae; many of these taxa are now in the phy-
lum Glomeromycota (see Redecker and
Schu ̈ssler 2014 ; Schu ̈ssler et al. 2001 ).
Several taxonomic treatments of Mucorales
s.l. were published in the first part of the twenti-
eth century (Benjamin 1979 ; Benny and Benja-
min 1975 ). Hesseltine’s ( 1955 ) classification of
Mucorales was later expanded (Hesseltine and
Ellis 1973 ) to include Benjamin’s ( 1959 ) meros-
porangiferous Mucorales. The classification pro-
posed by Benjamin ( 1979 ) is the basis for the
ordinal arrangement of many taxonomic
schemes (Alexopoulos et al. 1996 ;Kirketal.
2008 ). Benjamin ( 1979 ) recognized the orders
Mucorales, Entomophthorales, and Zoopagales,
validated Endogonales, Kickxellales, and Zoopa-
gales, and described Dimargaritales. His inclu-
sion of Harpellales (trichomycetes) (Lichtwardt
1986 ) in zygomycetes was less widely accepted
(Alexopoulos et al. 1995 ; Hawksworth et al.
1995 ). Much of the research in the two decades
between Benjamin’s ( 1979 ) review and that in
the first edition (Benny 2001 ; Benny et al. 2001 )
of this book was an attempt to create a more
natural morphology-based classification.
Batko (1964a,b,c,d) combined the diver-
gent taxonomic approaches of Nowakowski
( 1883 ) and Thaxter ( 1888 ) to provide the basis
for a more natural entomophthoralean classifi-214 G.L. Benny et al.