explained. Another light-microscopy study by
Wilson and Flanagan ( 1968 ) followed mitosis
in resistant sporangia and hyphae in
Brachyallomycesstrains and noted that somatic
nuclei were smaller than those in resistant spor-
angia.
Either closed mitosis or partially open
mitosis has been shown in fungi. So far,only
closed mitosis, or intranuclear division, has
been described in blastoclads. In closed mitosis
the nuclear membrane remains intact or largely
intact and the spindle forms inside the nucleus
(DeSouza and Osmani 2007 ; Heath 1980 ). A
persistent nuclear membrane during somatic
mitosis has been demonstrated inAllomyces
spp. (Olson 1984 ),C. anguillulae(Ichida and
Fuller 1968 ), andCoelomomyces indicus(Made-
lin and Beckett 1972 ). Lessie and Lovett ( 1968 )
reported intranuclear mitosis inB. emersonii
comprised of a typical microtubular spindle
apparatus and paired but unequal extranuclear
centrioles at each pole.
C. Taxis
Taxis refers to the ability of motile cells or
organisms to move across a gradient in a
directed manner. Such behavior is clearly
advantageous for zoospores and gametes of
blastoclads as they disperse to find a new food
source or mate. Both phototaxis and chemo-
taxis have been well documented in blastoclads.
Positive phototaxis toward light was demon-
strated in bothAllomyces spp. (Olson 1984 ;
Robertson 1972 ) and Coelomomyces(Martin
1970 ). Positive phototaxis may provide a mech-
anism by which gametes or zoospores may
emerge from sediments. The attraction of zoos-
pores ofAllomycesto cellulose and chitin irre-
spective of light has been shown (Mitchell and
Deacon 1986 ), as has positive chemotaxis
toward several amino acids (Machlis 1969 ;
Stumm et al. 1976 ).
Chemotaxis during mating should facilitate
motile gametes seeking a compatible partner.
The diffusible hormonesireninis produced by
female gametes ofAllomyces(Machlis1958a,b)
andhas activity at very low concentrations
(10–10to 10–5M) (Carlile and Machlis 1965 ).
Sirenin was the first fungal hormone to be
chemically characterized and shown to be a
bicyclic sequiterpenediol(Machlis 1968 ). Pom-
merville has also provided evidence that male
gametes produce a hormone, though the swim-
ming ability of female gametes is much reduced
compared to those of males (Pommerville 1977 ,
1978 ).D. Substrate Utilization and RespirationCompletely defined media have beenconstructed
for studying nutrition inAllomyces(Ingraham
and Emerson 1954 ). Growth on glucose, maltose,
and starch as a sole carbon source has been
shown forAllomyces(Ingraham and Emerson
1954 ),C. anguillulae(Nolan 1970 ), andB. pring-
sheimii(Crasemann 1957 ; Emerson and Cantino
1948 ; Gleason and Gordon 1989 ). Nitrogen utili-
zation varies among taxa, withAllomycescapable
of using inorganic nitrogen andBlastocladiella
andCatenariausing only organic sources(Bar-
ner and Cantino 1952 ). An absolute requirement
for an organic source of sulfur in the medium has
also been demonstrated for the saprotrophic
genera (Cantino and Turian 1959 ;Nolan 1969 ).
Nutritional studies have facilitated the isolation
of auxotrophic mutants; however, many mutants
reported in the literature have apparently been
unstable or displayed non-Mendelian inheritance
due to ploidy (Olson 1984 ).
The obligately biotrophic parasites have
been nearly impossible to isolate into pure
culture. Numerous methods employing a
“shotgun” approach have been tried for the
growth of Coelomomyces, which would have
clear benefits for biocontrol (Bland 1985 ;
Nolan 1985 ). Several media, such as BHM
(comprised of brain-heart infusion, mosquito
larval extract, fetal bovine serum, and corn
stunt spiroplasma media, to name a few ingre-
dients!), have supported the growth ofCoelo-
momyces, including the production of inviable
sporangia (Bland 1985 ; Castillo and Roberts
1980 ). Key to the successful deployment ofCoe-
lomomycesinoculum as a biocontrol agent will
be the in vitro culture of the gametophyte stage
from copepods, needed to produce infectiveBlastocladiomycota 199