Myxomycetes: Biology, Systematics, Biogeography and Ecology

Myxomycetes

Biology, Systematics, Biogeography, and Ecology

Edited by

Steven L. Stephenson

University of Arkansas, Fayetteville, AR

United States

Carlos Rojas

University of Costa Rica, San Pedro de

Montes de Oca, Costa Rica

Table of Contents

Cover

Title page

Copyright

Contributors

Preface

Introduction

Chapter 1: The Myxomycetes: Introduction, Basic Biology, Life Cycles, Genetics, and Reproduction

Abstract

Introduction

Morphology of Fruiting Bodies

Fruiting Body Types

Myxomycete Terminology

Myxomycete Life Cycle Stages

Genetics and Reproduction

Acknowledgments

Chapter 2: The History of the Study of Myxomycetes

Abstract

The Early Period

The First Scientific Studies

Arthur and Gulielma Lister

More Recent Studies in Europe

Studies in the United States

Studies Throughout the World

Future Studies of Myxomycetes

Chapter 3: The Phylogeny of Myxomycetes

Abstract

Introduction

Phylogenetic Revolution in Taxonomy

Marker Genes for Myxomycetes

Obtaining Sequences of Myxomycete DNA

How to Build a Tree?

Where are Myxomycetes in the Tree of Life?

Major Branches of the Myxomycete Tree

Morphology Versus Phylogeny

Chapter 4: Genomics and Gene Expression in Myxomycetes

Abstract

Introduction

Nucleolar DNA: Minichromosomes rDNA Genes

Chromosomes and Chromosomal DNA

Small, Noncoding RNAs

Mitochondrial DNA in Myxomycetes

Relationships Within the myxomycetes Based on mtDNA Structure

Insertional RNA Editing in the Myxomycetes

Concluding Remarks and Areas of Future Research

Chapter 5: Molecular Techniques and Current Research Approaches

Abstract

Part A:. A Synthesis of the Current Knowledge on Molecular Techniques Used for the Recording of Biodiversity and Ecological Analyses

Part B:. Comparative Molecular Biology and Use of Myxomycetes as Model Organisms

Chapter 6: Physiology and Biochemistry of Myxomycetes

Abstract

Introduction

Metabolites of Myxomycetes

Research Methods Used in the Study of Metabolites

Research Methods in the Study of Bioactivity

Acknowledgments

Chapter 7: Taxonomy and Systematics: Current Knowledge and Approaches on the Taxonomic Treatment of Myxomycetes

Abstract

Introduction

Definition of Taxonomy, Systematics, and Nomenclature

Brief History of the Taxonomy of Myxomycetes

Gross Systematics Within Myxomycetes

Taxonomic Literature on the Myxomycetes

Classification of the Myxomycetes (From Class to Genera, With References to the Protologue and a Brief Diagnosis of the Most Relevant Distinctive Characters)

The New Era of Taxonomy: How New Technologies Can Help to Resolve Classical Taxonomic Problems

Challenges in Taxonomy

Acknowledgments

Chapter 8: Ecology and Distribution of Myxomycetes

Abstract

Introduction

Methods of Study

Conclusions

Acknowledgments

Chapter 9: Biogeographical Patterns in Myxomycetes

Abstract

Introduction

Myxomycete Biogeography—What Can We See?

Two-Hundred Years of Fruiting Body-Based Diversity Research in Myxomycetes

Diversity and Species Composition of Myxomycete Communities From Major Ecosystems of the World

Acknowledgments

Chapter 10: Techniques for Recording and Isolating Myxomycetes

Abstract

Introduction

Field Collections

Isolation of Myxomycetes by Laboratory Culture

Conclusions

Acknowledgments

Chapter 11: Uses and Potential: Summary of the Biomedical and Engineering Applications of Myxomycetes in the 21st Century

Abstract

Part A:. Bioactive Compounds From Myxomycetes

Part B:. Myxomycetes in Unconventional Computing and Sensing

Chapter 12: Myxomycetes in Education: The Use of These Organisms in Promoting Active and Engaged Learning

Abstract

Introduction

Techniques

Conclusions

Acknowledgments

Chapter 13: Myxomycetes in the 21st Century

Abstract

Connection With the World

Research Perspectives

Conservation and Management

Putting the Pieces Together

Index

Copyright

Academic Press is an imprint of Elsevier

125 London Wall, London EC2Y 5AS, United Kingdom

525 B Street, Suite 1800, San Diego, CA 92101-4495, United States

50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States

The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom

Copyright © 2017 Elsevier Inc. All rights reserved.

No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions.

This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices

Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.

Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.

To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein.

Library of Congress Cataloging-in-Publication Data

A catalog record for this book is available from the Library of Congress

British Library Cataloguing-in-Publication Data

A catalogue record for this book is available from the British Library

ISBN: 978-0-12-805089-7

For information on all Academic Press publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Sara Tenney

Acquisition Editor: Kristi Gomez

Editorial Project Manager: Pat Gonzalez

Production Project Manager: Chris Wortley

Designer: Matthew Limbert

Typeset by Thomson Digital

Contributors

Andrew Adamatzky,     The Unconventional Computing Centre, University of the West of England, Bristol, United Kingdom

Nikki Heherson A. Dagamac,     Institute of Botany and Landscape Ecology, Ernst Moritz Arndt University Greifswald, Greifswald, Germany

Thomas Edison E. dela Cruz,     University of Santo Tomas, Manila, Philippines

Uno Eliasson,     University of Gothenburg, Gothenburg, Sweden

Arturo Estrada-Torres,     Behavioural Biology Centre, The Autonomous University of Tlaxcala, Tlaxcala, Mexico

Sydney E. Everhart,     University of Nebraska, Lincoln, NE, United States of America

Thomas Hoppe,     Institute of Botany and Landscape Ecology, Ernst Moritz Arndt University, Greifswald, Germany

Bruce Ing,     Applied Science and Environmental Biology, University of Chester, Chester, United Kingdom

Harold W. Keller

University of Central Missouri, Warrensburg, MO

Botanical Research Institute of Texas, Fort Worth, TX, United States of America

Courtney M. Kilgore,     Robeson Community College, Lumberton, NC, United States of America

Tetiana Kryvomaz,     Kyiv National Construction and Architecture University, Kyiv, Ukraine

Carlos Lado,     Royal Botanic Garden (CSIC), Madrid, Spain

Dmitry V. Leontyev,     H.S. Skovoroda Kharkiv National Pedagogical University, Kharkiv, Ukraine

Yu Li,     Engineering Research Center of Chinese Ministry of Education for Edible and Medicinal Fungi, Jilin Agricultural University, Changchun, Jilin, PR China

Pu Liu,     Engineering Research Center of Chinese Ministry of Education for Edible and Medicinal Fungi, Jilin Agricultural University, Changchun, Jilin, PR China

Dennis Miller,     University of Texas at Dallas, Richardson, TX, United States

Yuri K. Novozhilov,     Komarov Botanical Institute of the Russian Academy of Sciences, St. Petersburg, Russia

Ramesh Padmanabhan,     University of Texas at Dallas, Richardson, TX, United States

Carlos Rojas,     Engineering Research Institute, University of Costa Rica, San Pedro de Montes de Oca, Costa Rica

Adam W. Rollins,     Lincoln Memorial University, Harrogate, TN, United States

Subha N. Sarcar,     University of Texas at Dallas, Richardson, TX, United States

Martin Schnittler,     Institute of Botany and Landscape Ecology, Ernst Moritz Arndt University Greifswald, Greifswald, Germany

Margaret E. Silliker,     DePaul University, Chicago, IL, United States

Steven L. Stephenson,     University of Arkansas, Fayetteville, AR, United States

Hanh T.M. Tran,     Ho Chi Minh International University, Ho Chi Minh City, Vietnam

Laura M. Walker,     Smith College, Clark Science Center, Northampton, MA, United States

Qi Wang,     Engineering Research Center of Chinese Ministry of Education for Edible and Medicinal Fungi, Jilin Agricultural University, Changchun, Jilin, PR China

Katherine E. Winsett,     Wake Technical Community College, Raleigh, NC, United States

Diana Wrigley de Basanta,     Royal Botanic Garden (CSIC), Madrid, Spain

Preface

The myxomycetes (also called plasmodial slime molds or myxogastrids) have not been studied with the same intensity and geographical effort that have characterized many other groups of organisms. However, they are comparatively well known for being a group of microorganisms during much of their life cycle. The reproductive structures (fruiting bodies) produced by myxomycetes are often large enough be visible with the naked eye. Numerous examples are beautiful and their colorful miniature structures often capture the attention of both the trained and untrained eye.

It is commonplace to hear a wow or a similar expression of surprise when someone observes a specimen of myxomycete under a hand lens or microscope for the very first time. In fact, the same thing still happens to most myxomycete people when they see a new or unusual myxomycete, even after many years of studying these organisms. Edward O. Wilson popularized the concept of biophilia, which refers to the innate tendency of humans to seek connections with nature and other forms of life. Clearly, this applies to the microscopic world, including the myxomycetes, and is not likely to change any time soon. Hopefully, with this volume, more people will have the opportunity to develop an interest in both myxomycetes and other fascinating microscopic organisms as well.

It is our desire that this volume serve as a source of information that can help increase general bioliteracy by opening the door to the world of myxomycetes for the layperson, as well as representing a comprehensive reference work on the biology, systematics, biogeography, and ecology of the group for the expert. In the pages of this volume there is a considerable body of information on myxomycetes and their relationship with the world around them, as well as the modern scientific context within which they have been (and continue to be) studied. However, as is often the case with any comprehensive treatment of a group of organisms, these pages contain an even larger number of descriptions and accounts relating to laboratory and field stories, lifelong friendships and professional relationships, academic and nonacademic setbacks, financial stress, the problems of bureaucracy, and hundreds of thousands of miles traveled worldwide—using every possible means of transportation known to humans—all in the ongoing effort to learn more about myxomycetes. For this reason, the publication of this volume and all the work it represented was celebrated even before the first words were written.

This volume is the product of a collective effort of many individuals who have generated information on myxomycetes over a period of several decades. Of these, only the names of 29 coauthors from 11 countries appear. Consequently, we would like to acknowledge the extremely relevant support of field assistants, laboratory technicians, logistical staff members, and many others who have enabled the named individuals to generate the information presented in this volume. At the same time, we would like to acknowledge the support of multiple funding agencies over the years, without which much of the information that we now know about myxomycetes would not have been possible to obtain.

Our strong desire to communicate the scientific results that have been accumulated on myxomycetes has been the driving force in producing this volume. We have worked alongside numerous contributors, developing an updated and comprehensive treatment of a group of microorganisms for which the most comparable publication appeared almost 50 years ago. Since the present volume contains the work of many individuals from an earlier era, we would also like to acknowledge those now-historic figures who, in one way or another, were responsible for generating curiosity in others and thus provided the inspiration for modern researchers to carry out studies on this beautiful and challenging group of microorganisms.

At some point in our lives, there was someone who captured our attention and brought us into the world of myxomycetes. We all know the name of this person, different for each one, who influenced our careers more than any one of us could have known at the time. Hopefully, through this volume, the legacy of all of those who came before us can have a similar impact on someone, somewhere.

Steven L. Stephenson

Fayetteville, AR, United States

Carlos Rojas

Turrialba, Costa Rica

March 4, 2017

Introduction

Steven L. Stephenson*

Carlos Rojas**

* University of Arkansas, Fayetteville, AR, United States

** Engineering Research Institute, University of Costa Rica, San Pedro de Montes de Oca, Costa Rica

One of the earliest branches of the eukaryotic tree of life consists of an assemblage of amoeboid protists referred to as the supergroup Amoebozoa (Fiore-Donno et al., 2010). The most diverse members of the Amoeboza are the eumycetozoans, commonly referred to as slime molds, and the best known slime molds are the myxomycetes. The earliest published reference to a myxomycete (apparently Lycogala epidendrum) appears to have been made by the German botanist Thomas Panckow (1654), but some of the larger myxomycetes, such as Fuligo septica, have surely been noticed by humans for many thousands of years.

Since their discovery by scientists, the myxomycetes (also known as plasmodial slime molds, acellular slime molds, or myxogastrids) have been variously classified as plants, animals, or fungi. Because they produce aerial, spore-bearing structures which resemble those of certain fungi, and typically occur in some of the same ecological situations as fungi, myxomycetes traditionally have been studied almost exclusively by mycologists (Martin and Alexopoulos, 1969). Indeed, the name most closely associated with the group, first used by Link (1833), is derived from the Greek words myxa (which means slime) and mycetes (referring to fungi). However, abundant molecular evidence now confirms that they are amoebozoans and not fungi (Baldauf, 2008; Bapteste et al., 2002; Yoon et al., 2008). Interestingly, the fact that myxomycetes are protists was first pointed out by De Bary (1864), more than a century and a half ago, and he proposed the name Mycetozoa (literally meaning fungus animal) for the group. However, myxomycetes continued to be considered as fungi by most mycologists until the latter half of the 20th century.

Approximately 1000 morphologically recognizable species of myxomycetes have been described. The traditional approach has been to assign these to six different taxonomic orders, but recent evidence derived from molecular studies suggests that these orders do not hold together as they have been circumscribed in the past. As such, the system of classification used for the myxomycetes needs to be revised.

Myxomycetes are free-living predators of other eukaryotic protists and bacteria and have been recorded in every terrestrial habitat investigated to date. The two trophic stages in the life cycle (amoeboflagellates and plasmodia) are usually cryptic, but the fruiting bodies are often large enough to be observed directly in nature. Fruiting bodies release spores that are dispersed by air or, more rarely, by animal vectors. Under favorable conditions, these spores germinate and give rise to amoeboflagellates, from which the plasmodium is ultimately derived. Myxomycetes are associated with a wide variety of different microhabitats, the most important of which are coarse woody debris, ground litter, aerial litter, and the bark surface of living trees. Specimens for study can be obtained as fruiting bodies that have developed in the field under natural conditions or cultured in the laboratory. A substantial body of data on the worldwide biodiversity and distribution of the reproductive stage of myxomycetes has been assembled over the past 200 years, but only limited information is available for their trophic stages. More recently, an appreciable body of data has become available on various aspects of the biology, phylogeny, and genetics of these organisms.

The primary objective of this volume is to provide an overview of the majority of what is currently known about this truly fascinating group of organisms. This volume represents what might be regarded as a greatly expanded treatment of the type of information provided by Gray and Alexopoulos (1968) in Biology of the Myxomycetes and Martin and Alexopoulos (1969) in The Myxomycetes, both compiled almost a half century ago.

Virtually all of the more recent field-based publications relating to myxomycetes have focused on the distributional aspects of the group or the description of species new to science. This is largely due to efforts to increase the information available on these organisms in regions of the world where studies had never been carried out. Based on the body of new information that has been generated, it seems appropriate to produce an updated, comprehensive treatment of the biology, ecology, and taxonomy of myxomycetes.

Furthermore, an increased focus on molecular biology in recent decades has greatly increased the understanding of the genetics, phylogenetics, and biochemical systems present in the different groups of myxomycetes, and this type of critical information calls for a reinterpretation of myxomycete biology within a modern framework.

This volume also represents an effort to bring what is currently known about the biology and potential applications of myxomycetes to as broad an audience as possible. The intent of the editors and the collaborators has been to reach out to students, naturalists, and academics equally. Although this is a difficult task to accomplish, all of the individuals who have contributed to the information presented herein have worked with this in mind. The present volume has been designed to include important, updated, and revised chapters on the basic biology, ecology, and taxonomy of this group of microorganisms, along with discrete sections on such subjects as myxomycete biogeography; the history of studies of the group; the results of molecular-based studies; their management and conservation; and their educational value and potential applicability in the context of modern learning objectives for students at every academic level.

The chapter authors and coauthors were drawn from a group of acknowledged authorities who work with myxomycetes. Such an effort to include so many coauthors and a wide range of content is remarkable in the sense that a comprehensive volume including cross-related information and various perspectives on myxomycetes has not previously been produced. In this sense, the present volume also has an appreciable historical value with respect to documenting the current state of the art with respect to investigations directed toward myxomycetes in the first part of the 21st century. From a comparative point of view, readers of this volume will have the opportunity to understand how studies of myxomycetes carried out over the past couple of centuries have often lagged behind comparable studies of many other groups of organisms. However, the relevance and extent of the accomplishments made by a number of past and current individuals interested in the group also are described.

In addition to chapters dealing with different aspects of myxomycete biology, such as biochemistry, phylogeny, taxonomy, ecology, and distribution, readers will find that contextual topics, such as history of research, isolation techniques, biophilic potential, uses and applications, and educational value, have also been included. The idea behind this strategy has been to incorporate different approaches that are normally not considered in more difficult scientific texts but which are very important if one is to understand the context within which myxomycetes have been studied. An advantage of this type of approach is that readers are provided with additional tools to generate new lines of study within a modern context.

We invite the readers of this volume to become immersed in the fascinating world of myxomycetes. We encourage naturalists, science professionals, and policy makers to include these microorganisms in their agendas. We hope this volume generates necessary insights for an integrated development of studies of myxomycetes and energizes more people to appreciate the role of microorganisms in nature and, perhaps more importantly, the hidden and yet simple beauty of the natural microscopic world that lies beyond the capability of the human eye.

Acknowledgments

We are indebted to a number of individuals who were willing to review one or more chapters for us. These include Gražina Adamonyté, Charles Butterwell, Jim Clark, Uno Eliasson, Myriam de Haan, Eggehard Holler, Roland McHugh, Edward Haskins, Bruce Ing, Genaro Martinez, Wolfgang Marwin, Anna Ronikier, Wayne Rosing, Martin Schnittler, Frederick Spiegel, and Diana Wrigley de Basanta. We also thank Stephanie Somerville for the format revision of the complete volume.

References

Baldauf S. An overview of the phylogeny and diversity of eukaryotes. J. Syst. Evol.. 2008;46:263–273.

Bapteste E, Brinkmann H, Lee JA, Moore DV, Sensen CW, Gordon P, Durufle L, Gaasterland T, Lopez P, Muller M, Philippe H. The analysis of 100 genes supports the grouping of three highly divergent amoebae: Dictyostelium, Entamoeba, and Mastigamoeba. Proc. Natl. Acad. Sci. USA. 2002;99:1414–1419.

De Bary, A., 1864. Die Mycetozoen (Schleimpilze). Ein Beitrag zur Kenntnis der Niedersten Organismen, Leipzig, Germany.

Fiore-Donno AM, Nikolaev SI, Nelson M, Pawlowski J, Cavalier-Smith T, Baldauf SL. Deep phylogeny and evolution of slime moulds (mycetozoa). Protist. 2010;161:55–70.

Gray WD, Alexopoulos CJ. Biology of Myxomycetes. New York, NY: Ronald Press; 1968.

Link, J.H.F., 1833. Handbuch zur Erkennung der nutzbarsten und am häufigsten vorkommenden Gewächse, vol. 3. Spenerschen Buchhandlung, Berlin, Germany, pp. 405–422, 432–433.

Martin GW, Alexopoulos CJ. The Myxomycetes. Iowa City: University of Iowa Press; 1969.

Panckow, T., 1654. Herbarium Portabile. Berlin, Germany.

Yoon HS, Grant J, Teckle YI, Wu M, Chaon BC, Cole JC, Logsdon JM, Patterson DJ, Bhattacharya D, Katz LA. Broadly sampled multigene trees of eukaryotes. BMC Evol. Biol.. 2008;8:14.

Chapter 1

The Myxomycetes: Introduction, Basic Biology, Life Cycles, Genetics, and Reproduction

Harold W. Keller*,**

Sydney E. Everhart†

Courtney M. Kilgore‡

*    University of Central Missouri, Warrensburg, MO, United States of America

**    Botanical Research Institute of Texas, Fort Worth, TX, United States of America

†    University of Nebraska, Lincoln, NE, United States of America

‡    Robeson Community College, Lumberton, NC, United States of America

Abstract

In this chapter, the definitions of myxomycete terminology used to describe species are provided and also include the morphology of fruiting bodies, occurrences in habitats, and biology associated with life cycle stages. These terms include illustrations of fruiting bodies and structural parts along with publications and page numbers to guide the user to information sources. In addition, a review, discussion, and illustrations are provided that highlight life cycle stages represented by spores, myxamoebae, swarm cells, plasmodia, sclerotia, as well as fruiting body development and ploidy levels. Genetics, reproduction, and mating systems are discussed.

Keywords

myxamoeba

plasmodium

sclerotium

sporangium

spore

swarm cell

terminology

Introduction

What are myxomycetes? They are life forms that have baffled naturalists and scientists for more than 300 years. The first recorded observation in 1654 of the myxomycete Lycogala epidendrum fruiting bodies was by the German mycologist Thomas Pankow in his Herbarium Portatile, oder behendes Kräuter- und Gewächsbuch (see Chapter 2). Placement of the myxomycetes on the tree of life was controversial because different life cycle stages were emphasized over time by different researchers. A portion of the life cycle was considered animal-like and included in the Animal Kingdom; another portion was plant-like and included in the Plant Kingdom; and still another portion was considered fungal-like and included in the Fungi Kingdom. These organisms were also placed in the Protista Kingdom and more recently classified as Amoebozoans based on molecular evidence.

The historical name used for this group of organisms is myxomycetes (pronounced mix-oh-my-seats). This name was introduced by H.F. Link in 1833 in his Handbuch zur Erkennung der nutzbarsten und am häufigsten vorkommenden Gewächse. This treatment was used by the American myxomycologists Thomas H. Macbride, George W. Martin, and Constantine J. Alexopoulos. Another name for the group is Mycetozoa (literally fungus animals), introduced by the German mycologist Anton de Bary in 1859 and used mostly by European myxomycologists, especially the Listers (Arthur H. and daughter Gulielma) in three editions of their books published in 1894, 1911, and 1925 (Lister, 1894, 1911, 1925). The complete history of the taxonomy used for the myxomycetes and their placement in modern systems of classification are covered in detail in Chapters 3 and 7.

A review of myxomycete taxonomic history highlighted the past, present, and future (Keller, 2012), and encompassed the years from the 1700s and Linnaeus, through de Bary, Rostafińsky, the Listers, Macbride, Martin, Alexopoulos, and Farr, the latter four all being American myxomycologists of more recent time. This paper chronicles the history of the University of Iowa Myxomycete Collection and collectors, including eventual transfer of the collection to the National Fungus Collections (BPI) in Beltsville, MD, USA. The Myxomycete Collection at BPI numbers between 50,000 and 60,000 specimens, including many important type specimens. A current updated online inventory of myxomycete taxa, scientific binomials, and their authorities was consulted, and authority names will not be repeated here (Lado, 2005–16).

Myxomycetes are easy to find if you know what they look like and when and where to look for them. Generally, myxomycete fruiting bodies occur wherever there is sufficient decaying organic matter with adequate moisture and moderate temperatures. Some of the favorite collecting habitats on ground sites include forested areas with decaying logs, tree stumps, accumulated decaying leaves and needle litter, bark mulching around trees and shrubs, stacked wood piles, sawdust piles, compost heaps and garden mulching, hothouses with organic peat moss, basal dead leaves of ornamental flowers in flower beds, on piles of straw or baled hay in fields exposed to the weather elements, on bark of living trees and woody vines, on bark of living apple trees in apple orchards, on living lawn grass, and on herbivorous dung in pastures (Keller and Braun, 1999).

Many species have small fruiting bodies only a few millimeters in diameter and require a hand lens of 20× for detection. Weather-related conditions that favor the greatest diversity of species of myxomycetes are rainy periods that last several days with diurnal temperatures between 20 and 38°C; this coincides with the summer months of June–September in central and southeastern USA. Nivicolous (snowbank) myxomycetes occur in high-altitude mountainous regions of the world and develop under melting margins of snow cover in early springtime, usually in April and May in North America. In contrast, desert species of myxomycetes exhibit a surprising biodiversity in the Sonoran Desert of Arizona, occurring on the woody skeletons of cacti and dead parts of living plants in contact with the ground. Many new species have been discovered in arid habitats and desert regions throughout the world, whereas other species appear to be cosmopolitan and occur wherever decaying vegetation is present, for example, the tropics, temperate regions, wetlands (such as swamps, marshes, and bogs), grasslands, and even in the colder regions of the Arctic tundra and sub-Antarctic (Keller and Braun, 1999; Stephenson and Stempen, 1994).

Morphology of Fruiting Bodies

The spore-producing fruiting bodies of myxomycetes vary considerably in size. Some are tiny, less than 100 μm, and require microscopic examination; others are much larger, conspicuous, and visible to the naked eye, with dimensions up to 76 × 56 cm. The most common fruiting body type is a stalked sporangium, usually of definite size, shape, and color, with internal structural parts that are used to identify species. Stalked sporangia with spores propagate most species of myxomycetes, each with a combination of morphological characteristics either present or absent; externally a hypothallus and stalk, and internally a columella and a capillitium (system of threads) interspersed with spores and surrounded by an acellular peridium or wall (Fig. 1.1).

Figure 1.1   Sporangium of Echinostelium arboreum with labeled structural parts.

The fruiting body stage is used in dichotomous or synoptic keys to identify a particular species. Some shapes and colors are so distinctive that a species can be picture keyed or sight identified. However, most species require microscopic examination of spores and internal structures. Many species have look-a-like species that occur in similar habitats, with similar features, and require a careful collecting and microscopic characterization using myxomycete monographs. The world monograph, The Myxomycetes, by Martin and Alexopoulos (1969) was published almost 50 years ago, and is still considered by many to be the most authoritative text on the taxonomy of the myxomycetes. It has many technical terms used in species descriptions, but lacks a glossary with definitions or illustrations of descriptive terms. This limits its use by beginners, where more recently published books include such resources—for example, Stephenson and Stempen (1994) and Keller and Braun (1999)—and are a better choice for beginning students of myxomycetes. None of these books include many new species described in the last 50 years. There are now approximately 980 described species, based on the latest count in Lado (2005–16). Therefore, a more comprehensive list of myxomycete-related terms is defined here, and in some cases illustrated, with species examples and literature sources. The reader should consult the life cycle and structural terminology definitions, to better understand the terms that follow in the topical sections.

Fruiting Body Types

There are four fruiting body forms or types: sporangium, plasmodiocarp, aethalium, and pseudoaethalium. The sporangium may be stalked or sessile, often with a spherical-shaped spore case, and with a peridium that is acellular and surrounds the spores at some point during their development (Fig. 1.1). Spores are said to develop internally, and fruiting bodies are referred to as endosporous. Traditionally, there have been five recognized orders of endosporous myxomycetes: Echinosteliales, Liceales, Physarales, Stemonitales, and Trichiales. However, as outlined in Chapter 3, these taxa require revision based on recent molecular data. In certain minute species, a microscopic protoplasmodium produces only one sporangium, as in the genus Echinostelium (Martin and Alexopoulos, 1969) and a minute aphanoplasodium as in the genus Macbrideola (Martin and Alexopoulos, 1969). In contrast, phaneroplasmodial species, such as Physarum polycephalum (Fig. 1.2), produce a plasmodium that may grow to cover an area of a meter or more and form thousands of sporangia under ideal conditions (Keller and Braun, 1999; Martin and Alexopoulos, 1969; Stephenson and Stempen, 1994).

Figure 1.2   Bright yellow phaneroplasmodium of Physarum polycephalum on agar surface.

The plasmodiocarp is a sessile, elongated, worm-like, branched network or ring-shaped fruiting body, formed when the plasmodium concentrates protoplasm in situ in main veins during development. Hemitrichia serpula (Fig. 1.3) is one of the best examples of an entirely plasmodiocarpous habit (Keller and Braun, 1999; Martin and Alexopoulos, 1969) as is Perichaena chrysosperma, which is sporangiate to plasmdiocarpous (Martin and Alexopoulos, 1969). Several other species develop plasmodiocarps, with many in the Physarales. For example, Physarum compressum forms both stalked and sessile sporangia and plasmodiocarps (Martin and Alexopoulos, 1969) in the same cluster of fruiting bodies. Physarum cinereum forms sessile sporangia to short plasmodiocarps (Keller and Braun, 1999; Martin and Alexopoulos, 1969), as do Physarum superbum (Martin and Alexopoulos, 1969) and P. serpula (Martin and Alexopoulos, 1969). Laboratory experiments confirm that a single plasmodium can give rise to both stalked and sessile sporangia that intergrade into short or elongate plasmodiocarps of various lengths.

Figure 1.3   Plasmodiocarp of Hemitrichia serpula with peridium opened exposing yellow capillitial threads intermingled with yellow light-colored spores.

The aethalium is a large, sessile, round, or mound-shaped fruiting body formed from a single plasmodium, and is formed by all species in genera Fuligo and Lycogala (Figs. 1.4 and 1.5) (Martin and Alexopoulos, 1969; Stephenson and Stempen, 1994). These are the most widely known fruiting body types due to their relatively large size and frequent occurrence in urban landscapes. A world record aethalium of F. septica (76 × 56 cm) was discovered recently on the campus of the Botanical Research Institute of Texas on bark mulch (Keller et al., 2016).

Figure 1.4   Lycogala epidendrum aethalia broken open exposing pseudocapllitium and light colored spores covering piece of decayed wood.

Figure 1.5   Lycogala epidendrum aethalium closeup cut-away showing cortex warted surface and branching pseudocapillitial threads inside the spore chamber.

Although similar in outer appearance to an aethalium, the pseudoaethalium represents the fusion of many sporangia packed together (Fig. 1.6). The degree to which sporangia retain internal side-walls varies. Individual sporangia are only partially fused in species of Tubifera (Fig. 1.7), with the side-walls still intact (i.e., T. ferruginosa; Stephenson and Stempen, 1994). In Dictydiaethalium plumbeum, the tops of sporangia are still discernable, but internal side-walls do not separate each sporangium, and only the angles of the walls remain as threads (Keller and Braun, 1999).

Figure 1.6   Tubifera ferruginosa pseudoaethalia top view showing closely packed individual sporangia with tops and side-walls intact.

Figure 1.7   Tubifera ferruginosa pseudoaethalia closeup lateral view showing side-walls and tops of intact individual sporangia.

The stalked sporangium is the fundamental morphological unit found in most species of myxomycetes. However, these fruiting body types transition and intergrade into one another beginning with the sporangium that gradually undergoes transformation from individual discrete sporangia into worm-like plasmodiocarps. Then, through different degrees of sporangial fusion, it forms a pseudoaethalium where individual sporangia still retain their individual tops (in species of Dictydiaethalium and Tubifera), and finally, an aethalium may form, where the tops and side-walls become part of a much larger mound-shaped mass where the sporangia lose their individual identity. These fruiting bodies also intergrade from tiny, few-spored, stalked sporangia that grow on the bark surface of living trees and woody vines, to many thousands of sporangia producing many more spores, to a compound single, massive aethalium with thousands of spores on ground sites of decaying forest litter. These different fruiting body strategies for spore formation and release represent different evolutionary strategies for the dissemination of the maximum number of spores. A single phaneroplasmodium may form thousands of stalked sporangia with fewer spores per sporangium. In contrast, the plasmodiocarp and the aethalium form a single fruiting body to release thousands of spores. These fruiting body types occur in the different myxomycete orders, ensuring maximum spore formation and release.

Myxomycete Terminology

Myxomycete fruiting bodies are more conspicuous in natural habitats where they are collected for preservation in herbaria. This life cycle stage is used for the identification of species and is the basis for generic and species descriptions in monographs and other publications. A general review of the myxomycetes has updated the biodiversity inventory information, especially habitat descriptions and sampling (Spiegel et al., 2004), and in the same book a chapter on coprophilous fungi (Krug et al., 2004) has a limited section on myxomycete morphological terminology. Most technical terminology found in myxomycete publications is related to fruiting body occurrences and structural parts. Thus, a more comprehensive listing of defined morphological terms is included here, and examples found in myxomycete publications are provided with page numbers to facilitate location (Keller and Braun, 1999 = K & B; Martin and Alexopoulos, 1969 = M & A; Stephenson and Stempen, 1994 = S & S). Life cycle stages and reproductive and genetic terms are also included and defined (Figs. 1.8 and 1.9). Not every term found in literature sources is defined because some seem too vague and of questionable usefulness. Terms are arranged alphabetically.

Figure 1.8   Heterothallic life cycle for Physarum polycephalum.

Figure 1.9   Apogamic life cycle for Didymium iridis.

Acuminate tips: Referring to the sharply pointed tips of capillitial elaters in species of Trichia, such as T. botrytis that has long, sharply tipped elaters (M & A: 138, 498–499; S & S: Plate 14).

Allantoid spores: These spores are hotdog or sausage-shaped and are unique in the myxomycetes (Keller et al., 1975). Badhamia ovispora is the sole example.

Anastomosing: Interconnecting branches, usually refers to the capillitium, especially used for species in the genera Comatricha, Lamproderma (Fig. 1.10) and Stemonitis (Fig. 1.11) (M & A: 191–240, 508–521; S & S: 28, 161).

Figure 1.10   Lamproderma ovoideoechinulatum stalked sporangium.

(A) Peridium with reflected bright iridescent colors. (B) Central profile showing columella rising to midpoint with attached capillitial threads branching and anastomosing with free tips at the periphery.

Figure 1.11   Stemonitis smithii: (A) surface view of sporangium showing capillitial network as a surface net with no free ends. (B) Sporangium in optical section with central columella giving rise to branching and anastomosing capillitium that unites at the surface as a surface net.

Amoeboflagellates: A general term that refers to the haploid myxamoebae and haploid swarm cells (potential gametes) in the myxomycete life cycle, capable of interchanging developmentally based on the presence or absence of free water (Fig. 1.8).

Angular: Having angles or sharp corners, frequently used to describe the calcareous nodes in physaroid capillitium (Figs. 1.12 and 1.13). Angular calcareous nodes are described in Physarum cinereum, P. contextum, P. leucopus, and many other species of Physarum (M & A: 295, 307, 532–533, 536–537; S & S: 143–144).

Figure 1.12   Physarum bruneolum: entire intact stalked sporangium (A) showing thickened calcareous peridium and hypothallus at base of stalk. (B) Image with cut-away interior showing physaroid capillitium of angular calcareous nodes connected to hyaline noncalcareous threads.

Figure 1.13   Craterium leucocephalum: (A) stalked sporangium with basal cup and white calcareous mostly angular nodes. (B) Centrally suspended calcareous pseudocollumella.

Aphanoplasmodium: A plasmodial type characterized in its early stages of development by a network of flattened, thread-like, transparent, almost invisible strands that lack polarity and directional movement. These early stages lack distinct ectoplasmic and endoplasmic regions, and the streaming protoplasm is not coarsely granular. Free water favors early stages of development on agar cultures. Members of the Stemonitales and the genera Comatricha, Lamproderma, and Stemonitis are examples of this group.

Apogamy (adj: apogamous): The condition of a myxomycete having a nonsexual life cycle without ploidy variation and therefore no fusion of haploid gametes (Fig. 1.9).

Apomixis (adj: apomictic): A life cycle where meiosis and subsequent fusion of gametes do not occur so that all stages are diploid (Fig. 1.9).

Arcuate: Curved like a bow, in reference to fruiting body shape. P. chrysosperma often has arcuate, sessile, plasmodiocarps (M & A: 110–111, 492–493).

Areolate: Having a pattern of block-like areas or polygons on the peridium, as in Trichia floriformis dehiscence (M & A: 161, 498–499).

Assimilative (trophic) phase: These are the myxamoebae, swarm cells, and plasmodia life cycle stages that are the feeding or nourishment phases (Fig. 1.8).

Asperulate: Appearing rough because of small warts or spines, as in Physarum polycephalum spore surface ornamentation (S & S: 148–149).

Attenuated: Gradually narrowed downward as the stalk of Hemitrichia clavata (M & A 148) and narrowed upward as the stalk of Clastoderma (K & B: 73–76; S & S: 95–96).

Axenic cultures: These cultures have only a single living species throughout the time-course of growth and development, with no other contaminating organisms present.

Badhamioid: A type of capillitium consisting of a network of calcareous tubules found in species of Badhamia (Fig. 1.14). This character is extremely variable, sometimes appearing physaroid, with a network of threads lacking calcium carbonate in species that typically have a network of calcareous tubules (K & B: 28; M & A: 324–325; S & S: 31).

Figure 1.14   Badhamia panicea showing badhamoid calcareous capillitial network.

Bacteriovores: Any organism that feeds on bacteria as a source of food. Myxomycete myxamoebae and free-living plasmodia feed primarily on bacteria, and also on yeasts, fungal spores, algae, and possibly as opportunists engulfing other microorganisms, thus acting as microbial predators.

Bordered reticulate: A distinctive spore ornamentation with a raised episporic network that appears to give the spore a border in optical section as seen with a compound microscope at 400–1000×. The size and numbers of the meshwork as seen in surface view are used in species descriptions and as key characters (Fig. 1.15C); Comatricha rispaudii, Hemitrichia serpula, and Perichaena reticulospora are a just few examples (K & B: 31; M & A: 152–153, 502–503; S & S: 34).

Figure 1.15   Spore ornamentation types: (A) spiny; (B) warted; (C) reticulate; and (D) smooth.

Bright (light)-spored: Having spores that are bright (light or pallid) colors in mass seen as hyaline, white, gray, yellow, orange, pink, and red. The orders Echinosteliales (Echinostelium and Clastoderma) and Trichiales with species in the genera Arcyria (Fig. 1.16B–C), Hemitrichia (Fig. 1.3), Metatrichia, Perichaena, and Trichia are members of this light-spored group (K & B: 40, 169–170; M & A: 110–165, 492–503; S & S: 35).

Figure 1.16   Fruiting body development of Arcyria ferruginea: (A) immature stalked sporangia in early stages of formation before final mature shape. (B) Sporangia freshly mature still in moistened state showing basal calyculus. (C) Gregarious mature orange sporangia with powdery light-colored spore mass and expanded elastic capillitial threads.

Bryophilous (musicolous) myxomycetes: Epiphytic species associated with and fruiting on liverworts and mosses. Licea bryophila and L. hepatica exclusively sporulate on liverworts, and L. gleoderma exclusively sporulates on mosses on the bark of living trees (Ing, 1994).

Bulbous: Referring to the bulb-like swollen tips of the elaters in some species of Trichia, for example, T. lutescens (M & A: 162).

Caespitose: Growing in clusters or dense tufts. Comatricha caespitosa takes its specific epithet from the dense tufts or clusters of stalked sporangia (M & A: 226–227, 512–513). Most Stemonitis species are caespitose, for example, S. axifera, S. fusca, and S. splendens among others (K & B: 171; M & A: 191–199, 508–511; S & S: 153, 154 Plate12).

Calcareous bodies (lime knots): Granular calcium carbonate, CaCO3, in the Physaraceae is found in the capillitium as calcareous nodes, deposited as a covering on the peridium in varying thickness and layers, in the stalk and extending into the columella in the spore chamber. In the genus Physarum, expansions in the capillitial threads contain granular calcium carbonate (lime knots) interconnected by noncalcareous threads (Fig. 1.12). Use of the word lime (calcium oxide, CaO) in myxomycete literature is incorrect when it is substituted for calcium carbonate. Examples include many species of Physarum (K & B: 28).

Calyculus: A cup, referring to the persistent peridium forming a cup at the base of a sporangium. Most species in the genera Arcyria (Fig. 1.16C) and Cribraria have a calyculus. The depth and surface markings on the cup can be found in species descriptions (M & A: 91, 488–489; S & S: Plate 2, E–H).

Capillitium: A system of sterile threads usually attached to the columella, either simple or branching and anastomosing, to form a network intermingled with the spores inside the fruiting body (most species of myxomycetes). This definition refers to a true capillitium that occurs in the orders Echinosteliales (Fig. 1.1), Trichiales (Fig. 1.3), Physarales (Fig. 1.14), and Stemonitales (Fig. 1.11). These threads form from a system of preformed vacuoles that coalesce, giving rise to solid or hollow threads often with debris and of uniform diameter usually less than 6.0 μm. Threads in Arcryia species are more or less elastic and expand at maturity (Fig. 1.16C).

Centrioles (basal bodies): Cylindrical cell organelle of eukaryotes found in pairs in cytoplasm near the nucleus of flagellated cells (swarm cells) composed of the 9 + 2 arrangement of microtubules.

Cartilaginous: Consisting of a rather uniformly thickened peridial layer in some species of Diderma, especially D. floriforme and D. trevelyani, which have multiple calcareous layers. Peridial layers may be described as single, double, or triple and are often difficult to interpret accurately because of tight adhesion (M & A: 357–358, 371–372, 548–549, 552–553; S & S: 112–113, Plate 13A).

Cinereous: Resembling the color of ashes, bluish gray, represented by the fruiting bodies of Physarum cinereum, a common species frequently occurring on living St. Augustine lawn grass (K & B: 127, 174; M & A: 291–292, 532–533; S & S: 143–144).

Circumscissile: Refers to a dehiscence pattern where a special thin-walled area forms an encircling line usually around the apex of the sporangium. The best examples are Perichaena corticalis (M & A: 111–112, 492–493; S & S: Plate 15A) and Metatrichia vesparium (K & B: 169; M & A: 143–144, 502–503; S & S: 137–138).

Clavate: Club-shaped. Wider and thicker at the apex and narrower at the base. Generally applied to the shape of the sporangium as in the club or turbinate shape of H. clavata (M & A: 148, 502–503).

Clustered spores (spore balls): Spores adhering together in loose or tight clusters of 2–40, characteristic of some Badhamia species, including B. bispora, B. capsulifera, B. crassipella, B. nitens, B. papaveracea, B. populina, B. utricularis, and B. versicolor. This character also occurs scattered in other taxa, for example, Dianema corticatum, Didymium synsporon, Macbrideola synsporos, Minakatella longifila, Perichaena syncarpon, and Trichia synsporon. An interior cavity may be present or absent in spore clusters. The spore shape may be nearly spherical in loose clusters but distinctly ovate or pyriform in tight clusters. Spore clusters provide a diagnostic character useful in separating species in keys and species descriptions, for example, free spores versus clustered spores (K & B: 28; M & A: 251–261, 522–525; S & S: 34).

Coenocyte (syncytium): From multiple fusions and referring to the myxomycete plasmodium, a large amorphous mass of protoplasm not separated into individual cells, containing many nuclei and surrounded by a membrane (Figs. 1.2 and 1.8).

Cogs: Square-ended projections similar to cogs on a wheel, often accompanied by rings, half-rings, plates, reticulations, and minute spines. Capillitial threads of Arcyria species usually have ornamentation that includes cogs as part of the surface markings (M & A: 123–137, 494–497).

Coiled: A structure twisted around on itself, as in the capillitial threads of Metatrichia vesparium (M & A: 143–144, 502–503; S & S: 137–138, Plate 15).

Columella: A dome-shaped, spherical, or elongated central sterile structure within the sporangium that represents an extension of the stalk into the spore chamber (Figs. 1.10 and 1.11). It may be of various sizes and may serve as a supporting structure for the capillitium that may be attached in part or throughout its length. It may be a short protrusion or extend to the top of the sporangium. The columella, when present, is an important part of the species description, and is used in keys to identify the different species. This structure is absent in species of the Liceales and Trichiales.

Compressed: Flattened laterally as in the stalked sporangia of Physarum compressum that are compressed into a fan shape (M & A: 293, 532–533).

Conical: Cone-shaped, with a broad circular base and tapering to a point at the top. Lycogala conicum can be sight identified in the field because of its large conical fruiting body hence the specific epithet (M & A: 63–64, 482–483).

Coprophilous (fimicolous) myxomycetes: Species that grow and sporulate on mostly mammalian dung of herbivorous animals. A few species are obligate and are only known from dung, for example, Kelleromyxa fimicola, Licea alexopouli, and Trichia brunnea. These three species have evenly and greatly thickened spore walls without a thin-walled area or germination pore and appear to have adapted to passage through the intestinal tract of grazing herbivores (Eliasson and Keller, 1999; Krug et al., 2004).

Cortex: Thickened calcareous outer covering of the aethalium in the genus Fuligo (M & A: 266–267, 526–527; S & S: 123–124). This structure appears in all Fuligo species descriptions instead of the term peridium because it generally functions in the same way, protecting the black spore mass inside. Fuligo septica is a conspicuous example because of its large size (Keller et al., 2016) and well-developed cortex of calcareous granules. Mucilago crustaea also has a thickened cortex, but in this case, it is composed of crystalline not granular calcium carbonate. It is a look-alike species sometimes misidentified as F. septica since both are common species found in similar habitats.

Corticolous myxomycetes: This group of myxomycetes develops, grows, and sporulates on the bark surface of living trees and woody vines (Everhart et al., 2008;  2009; Snell and Keller, 2003). Most species have microscopic plasmodia (protoplasmodium or a reduced aphanoplasmodium) that exhibit rapid sporulation, usually in less than 24 h. These plasmodia produce single, tiny (less than 1 mm), stalked sporangia with an evanescent peridium and quick spore release. Life cycle stages, such as spores, microcysts, and sclerotia, are resting dormant stages capable of surviving unfavorable environmental conditions and reviving quickly when favorable conditions return, much like desert ephemeral plants. Most Echinostelium and Macbrideola species have tiny stalked sporangia that are the best examples of this short-lived life cycle strategy (Keller and Everhart, 2010).

Crowded: Refers to the species habit where fruiting bodies are massed or tightly packed together. Examples include several from the Trichiales: Oligonema schweinitzii, Calonema aureum (K & B: 163F), Metatrichia vesparium, Trichia favoginea, and many Arcyria species, including A. denudata, A. nutans, and A. versicolor (M & A: 119–121, 126–127, 133–134, 136–137, 143–144, 160–161, 492–497; S & S: 137, 156–157, Plate 14A, Plate 15B).

Crystalline calcareous bodies: Loose crystals or scales scattered on the surface of the peridium (Fig. 1.16), or compacted to form a smooth eggshell-like outer crust, as in the genus Didymium. Two different groups of species are recognized: one based on the type of crystals such as the stellate or star-shaped crystals found on the peridium of D. iridis (Fig. 1.17) (S & S: 117–118) and D. squamulosum. The other group has an eggshell-like outer crust of compacted crystals that gives an outward appearance of Diderma species as in Didymium difforme and D. quitense. Members of the latter group are sometimes misidentified as Diderma species when there is failure to examine fractured peridial surfaces for protruding tips of crystals. A unique rhombohedral crystal was described from the stalk of Diachea arboricola using scanning electron microscopy (SEM) images (Keller et al., 2004).

Figure 1.17   Stellate crystals covering peridial surface typical of Didymium iridis sporangia.

Cylindrical: A structure that has the same diameter throughout its elongate length. Usually applied to the general shape of a sporangium, as in Diachea leucopodia (M & A: 178–179, 506–507; S & S: 107–108, Plate 4).

Dark-spored: Having spores in mass that are black or dark brown, such as the Physarales and Stemonitales (known as the dark-spored orders) (Figs. 1.10 and 1.18).

Figure 1.18   Lamproderma retirugisporum stalked sporangia showing bluish iridescent peridia with black spores scattered on surface.

Dehiscent: Peridium splitting open at maturity along thinner lines like the petals of a flower as in Diderma floriforme, or like a star, as in D. asteroides, D. radiatum, or D. trevelyani.

Dextral: A term sometimes used to describe the winding in a right-handed direction of the spiral bands around the capillitial threads in Hemitrichia and Trichia species.

Dichotomous: Refers to the branching pattern of the capillitium forking into two more or less equal parts as in Lamproderma muscorum and Macbrideola cornea.

Dictydine (plasmodic) granules: Microscopic (0.5–3.0 μm), usually dark-colored, strongly refractive spherical granules that are found only on fruiting bodies in the genera Cribraria, Dictydium, and Lindbladia. In species of Cribraria the dictydine granules are prominent on the peridial network and the calyculus (cup) when present. In Lindbladia these granules were characterized using SEM and X-ray microanalysis and shown to be hollow and contain calcium (Hatano et al., 1996). Earlier researchers (the Listers) assumed that the dark granules in the plasmodium were the source of the same granules on the fruiting bodies; hence they introduced the term plasmodic granules. However, since there has never been a developmental study to determine the origin and final deposition of these structures, dictydine granules is the preferred usage until more data from developmental studies are available. For a more detailed historical review of these terms, see Hatano et al. (1996).

Duplex: Refers to two types of capillitium as in Leocarpus fragilis (K & B: 173, Plate 13; S & S: 130), with a network of calcareous tubules connected to or distinct from a mostly noncalcareous system of capillitial threads, and as in Willkommlangea reticulata [M & A: 243–244, 522–523 (as Cienkowskia); S & S: Plate 9B], with a capillitium of angular, flattened, calcareous nodes massed transversely as plates and slender, delicate, anastomosing threads forming a loose or dense net, mostly noncalcareous, or with a few calcareous nodes and numerous short, sharp-pointed branchlets.

Effused: A term applied to the habit of the fruiting body when thinly spread out and flattened on the surface of the substratum. The effused condition is found frequently in different species, but one special example is the broadly effused white fruiting bodies of Diderma effusum (M & A: 356–357, 546–547; S & S: 111) growing on decayed leaves.

Elaters: Free, usually unbranched and unattached, capillitial threads marked with spiral bands characteristic of species in the genus Trichia. These elastic threads are hygroscopic and undergo twitching movements that serve to disperse the spores in response to humidity changes in the surrounding environment (K & B: 29, 169; M & A: 160–161, 498–501; S & S: 155–159).

Endosporous: Having spores borne enclosed within a peridium (Fig. 1.10), such as in the orders Echinosteliales, Liceales, Trichiales, Physarales, Stemonitales. The order Ceratiomyxales has spores borne externally but this group is no longer included in the myxomycetes based on recent molecular evidence.

Epihypothallic development: A developmental type where stalked sporangia develop from the aphanoplasmodium through a series of individual primordial changes as the protoplasm condenses and concentrates into separate blebs that represent the sporangial initials destined to form the individual sporangia. The hypothallus forms on the lower side of the presporulating plasmodium and directly on the surface of the substratum. The stalk material is deposited at equidistant points on top of the hypothallus and elongates as more material (secreted internally from within the protoplasmic mass) is added to the tip of the stalk, carrying the prespore mass upward (Keller, 1982). This can be seen in time-lapse photography as the stalk forms first as a black line and the prespore mass appears to climb the stalk in dramatic fashion, and eventually forming the dark spore mass. This developmental type is characteristic of the Stemonitales as seen in several Comatricha, Lamproderma, and Stemonitis species.

Evanescent: Refers to a peridium that often disappears early in development in certain species of Arcyria, Comatrichia, Macbrideola, and Stemonitis (Fig. 1.11).

Extranuclear mitotic (open) division: Refers to mitotic nuclear division in myxamoebae wherein an extranuclear spindle forms and the nuclear membrane disappears during division.

Floricolous myxomycetes: An assemblage of species associated with the inflorescences of large neotropical living herbs, such as Heliconia and Costus, where rapidly decaying floral parts are enclosed by living bracts (Schnittler and Stephenson, 2002).

Foliicolous myxomycetes: Species restricted to growing and sporulating on decaying leaves on ground sites.

Fruiting body: A general term for the spore-bearing structure, also known as sporophore, sporocyst, spore case, sporotheca, or fructifications (Clark and Haskins, 2014).

Fugacious: Having a peridium that disappears soon after development, as in species of Cribraria, where portions are gone at maturity, resulting in a peridial network in the upper half of the spore case above the calyculus. Interstices of the peridial network are probably extremely thin and the membrane ephemeral because there is no evidence of its presence with scanning electron microscope observation.

Fungicolous myxomycetes: Species that feed and grow on fungi. Physarum polycephalum is a good example of a bright yellow phaneroplasmodium that feeds on and covers Pleurotus ostreatus (the oyster mushroom) and Lentinus tigrinum on decaying stumps, bark, logs, and the base of standing dead trees on ground sites (Keller et al., 2008). Badhamia utricularis also occurs on a wide variety of wood-rotting fungi, including Stereum hirsutum and Phlebia radiata, as a chrome-yellow plasmodium on decaying logs and forms extensive colonies of weakly stalked sporangia (Ing, 1994). These myxomycetes occur so frequently in this association with fungi it cannot be ascribed to chance.

Gregarious: A term used to describe the general habit when fruiting bodies grow in closely associated groups but not touching (as in crowded or heaped habits) or solitary. These terms are used in species descriptions to describe