Systematics and Evolution, Part A The Mycota

7 Blastocladiomycota

TIMOTHYY. JAMES^1 ,TERESITAM. PORTER^2 ,W.WALLACEMARTIN^3

CONTENTS

I. Introduction............................... 177

II. Occurrence and Distribution............. 179

A. Saprobic Species........................ 179

B. Invertebrate Parasitic Species .......... 180

C. Plant-Pathogenic Species............... 180

D. Mycoparasites.......................... 180

E. DNA-Based Evidence ................... 180

III. Structure of Thallus and Reproductive

Characters.................................. 181

IV. Phylogeny and Systematics............... 182

A. Phylogenetic Placement

of Blastocladiomycota .................. 182

B. Phylogenetic Classification

of Blastocladiomycota .................. 184

V. Life Cycles.................................. 187

A. Historical Perspective .................. 187

B. Life Cycles ofAllomyces................ 187

C. Life Cycles of Other Blastocladiomycota 189

VI. Zoospore Ultrastructure.................. 192

A. Historical Perspective .................. 192

B. Generalized Structure of Motile Cells

of Blastocladiomycota .................. 193

1. Axial Assembly....................... 193


2. Microbody–Lipid Globule Complex. 194


3. Flagellar Apparatus .................. 196


4. Cytoplasmic Inclusions .............. 196
   VII. Genetics and Physiology.................. 197
   A. Hybridization........................... 197
   B. Mitosis .................................. 198
   C. Taxis..................................... 199
   D. Substrate Utilization and Respiration. 199
   E. Genomics................................ 200
   VIII. Conclusions and Future Directions...... 201
   References.................................. 202

I. Introduction

Blastocladiomycota arezoosporic fungi that

comprise an early-diverging branch on the

tree of true fungi possessing a number of dis-

tinguishing morphological and life history

characteristics. These aquatic and soil fungi

include genera typically considered so-called

water molds, occurring as saprotrophs on

decaying plants and animals. Other members

of the clade are obligate parasites of

invertebrates, plants, and algae. Beyond a

basic understanding of global biodiversity,

Blastocladiomycota present avenues for excit-

ing research: they have served as models for

fungal genetics and physiology (Olson 1984 ;

Ribichich et al. 2005 ), they have potential as

biocontrol agents of plant pests and disease

vectors (Chapman 1985 ; Garcia 1983 ; Singh

et al. 2007 ), and they interact with aquatic

food webs and nutrient cycling through para-

sitism and consumption (Johnson et al. 2006 ).

Convenient terms for the group includeblasto-

dadandblastoclad, and we adopt the latter in

reference to any fungus belonging to this phy-

lum.

The blastoclads were historically consid-

ered to be closely related to other zoosporic

true fungi, the Chytridiomycota (chytrids),

because they reproduce with zoospores posses-

sing a single posteriorly directed flagellum

(Sparrow 1960 ). Blastocladiomycota, as well as

the two zoosporic fungal phyla Chytridiomy-

cota and Neocallimastigomycota, were shown

to be members of the fungal kingdom in the

earliest ribosomal DNA–based molecular phy-

logenies (Bowman et al. 1992 ; Bruns et al. 1992 ;

(^1) Department of Ecology and Evolutionary Biology, University
of Michigan, 830 N. University, Ann Arbor, MI 48109, USA;
e-mail:[email protected]
(^2) Biology Department, Duke University, Durham, NC 27708,
USA and Department of Biology, McMaster University, Hamil-
ton, ON L8S 4K1, Canada; e-mail:[email protected]
(^3) Department of Biology, Randolph-Macon College, Ashland,
VA 23005, USA; e-mail:[email protected]
Systematics and Evolution, 2ndEdition
The Mycota VII Part A
D.J. McLaughlin and J.W. Spatafora (Eds.)
©Springer-Verlag Berlin Heidelberg 2014