Fungi from Different Environments

J K Misra

• Publisher: CRC Press
• Year: 2019
• Print ISBN: 9781578085781
• eBook ISBN: 9780429526688
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

Mycologists now look at the genes of fungi to decipher many features that they have been studying in the past beyond just looking at the morphology and other such traits of these organisms. Fungi are also attracting the attention of scientists in various other disciplines. These include the search for useful fungi in various extreme environments th

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Fungi from Palaeoenvironments: Their Role in Environmental Interpretations

S.K.M. Tripathi

Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow 226007, India

E-mail: [email protected]

Abstract

Fragments of fossil fungal remains are commonly seen in macerated residues prepared for palynological studies. These are less frequent in samples from Palaeozoic strata but are better represented in preparations of Lower Mesozoic sediments. A great spurt in fungal diversity is witnessed in the Tertiary Period. Except for some distinctive Tertiary forms, fossil fungal remains can not be generally ascribed to modern taxa, hence, their classification with living fungi is not possible. Fossil fungal remains are, therefore, described as Form Genera under the Artificial System of classification which is based on morphological characters only However, wherever possible their affinities with extant forms are provided.

Innumerable variety of fossil fungal remains are described as spores, filaments, fruiting bodies and mycorrhiza which have been reported from Cretaceous to Tertiary sediments. Ascomycetous fungal remains got well-established during the Cretaceous time and became conspicuously abundant by the Tertiary Period. Enormous varieties of fossil fungal spores are reported from these sediments. Fossil spores are described under “Dispersed Spores” which include detached spores, microscopic sporangia and fragmented mycelia. Based on characters associated with size, symmetry, pores and septa, the spores are described under different morphologic groups. Fruiting bodies of epiphyllous fungi are commonly found in Tertiary sediments. These can be compared with extant forms with greater accuracy than the spores. The fruiting bodies or the ascocarps are variously shaped ostiolate or non-ostiolate bodies made up of radiating rows of mycelia giving an appearance of tissues arranged in a radiating fashion. The ascocarps contain asci.

Fossil fungi provide significant information about the past habitats and the hosts. Fossil epiphyllous fungi are more reliable and advantageous for palaeoclimatic interpretations. Occurrence of these fossils reflects moist and humid climate of tropical to subtropical belts. Studies particularly focusing the host fungus relationship are of great significance in attempting the palaeoenvironmental interpretations. This chapter encompasses the aforesaid aspects of fungi from palaeoenvironment.

INTRODUCTION

Palaeomycology, the study of fossil fungi, is still in its infancy. The main reason for this is the lack of adequate knowledge amongst the palaeontologists about fungal morphology. Furthermore, the general feeling that fungal remains are less useful for stratigraphical interpretations has been one of the many other factors for their neglect. Fossilized fungi are represented by their hyphae, fructifications and the dispersed spores. These have been recorded sporadically since long (Williamson, 1878, 1880; Kidston and Lang, 1921; Edwards, 1922). Most of the fossil fungal remains reported earlier are poorly described and badly illustrated. However, since the 1950s their study received more attention with the development of palynology. During the last couple of decades fossilized remains of fungi have been investigated with greater interest involving phylogenetic, biostratigraphic and palaeoenvironmental implications (Ramanujam, 1982; Taylor and White, 1989). Fungal remains are very resistant to chemical and biological degradation and are easily recoverable from rocks. These are commonly seen in palynological preparations. Fossil fungal remains are less common in Palaeozoic strata but become more frequent in Lower Mesozoic. A great sprut in the fungal diversity is witnessed in Tertiary Period. Records show that proliferation of fungi is linked with diversification of angiosperms. This chapter embodies the classification of fossil fungi, their geological records, the stratigraphical considerations and palaeoclimatic interpretations with suggestions for future research.

CLASSIFICATION OF FOSSIL FUNGI

Fossil fungi are fragmentary in nature and lack of characteristic features that are diagnostic of extant taxa. Except for some distinctive Tertiary forms, most of the fossil fungal remains can seldom be matched with modern taxa hampering their classification under the Natural System. Problems concerning the nomenclature and classification of fossil fungi have been discussed by various workers from time to time (Elsik, 1968, 1976; Pirozynski and Weresub, 1979). It has been argued by these workers that assigning most of the fossil forms a modern name will lead to taxonomic confusion and it will, therefore, be more convenient and logical to describe the fragmentary fossils as form genera on the basis of their morphological characters only. Under this scheme fossils are assigned artificial generic and specific names and wherever possible their affinities with extant taxa are ascribed. While dealing with the pertinent groups, characters taken into account for classification of different types of fungal remains have been elaborated. Fossil fungal remains have been dealt with here in two categories—the Fungal Spores, and the Epiphyllous Fungi. In addition to these, some specific and special fossil fungi described from Cretaceous and Tertiary sediments of India have been discussed.

A brief comment on some important fossil fungal remains highlighting their morphological features and the palaeoenvironmental significance has been mentioned in the present contribution.

As evidenced by the fossil records, Ascomycetes, the largest and most diversified group of modern fungi, got well-established during the Cretaceous time and became conspicuously abundant by the Tertiary Period (Jain, 1974; Jain and Kar, 1979; Jansonius, 1976; Ramanujam, 1982; Kalgutkar and Jansonius, 2000). Fungi of this group produced ascospores and coniodia which helped them to thrive in a variety of habitats as saprophytes, parasites, epiphytes and mycorrhiza. The Early Tertiary palynological assemblages are markedly characterized by increased number of epiphyllous fungi which were hosted by broad angiospermous leaves.

I. Fungal spores

Enormous varieties of fossil fungal spores are found in Late Cretaceous to Cenozoic sediments. These are described under ‘dispersed spores’ which include detached spores found in rocks, microscopic sporangia and hyphae or fragmented mycelia. In a classification system proposed by van der Hammen (1956) fossil fungal spores were grouped under various morphologic categories with the suffix ‘Sporites’. Clarke (1965) proposed the suffix ‘Sporonites’ for naming the fossil fungal spores. Considering the characters such as, shape, size and symmetry of spores, absence/ presence and number of apertures, septa characters and the wall features, Elsik (1976) attempted to prepare a comprehensive and applicable taxonomy for the fossil spores. He proposed artificial supra-generic categories for classification of fossil fungal spores. These categories were primarily based on the cell number and presence or absence of apertures. Under these categories artificial genera and species could be conveniently described. Pirozynski and Weresub (1979) suggested a system called ‘Saccardoan System’ for classifying the fungal spore types. Under this scheme, based on number of cells and shape, the fungal spores may be classified as Amerospores (monocellate), Didymospores (dicellate), Phragmospores (trito multicellate), Dictyospores (muriform), Scolecospores (filiform), Helicospores (spirally coiled) or Staurospores (star-like). A brief description of different taxa classified under various groups of fungal spores is given in Table 1. The majority of fungal spores found in palynological preparations belong to Ascomycetes. Only a few questionable spores of Basidiomycetes have been described in some fossil assemblages. Palynological assemblages are often rich in different varieties of Conidia. These are produced by Fungi Imferfecti and the holomorphic ascomycetes. They may be one-celled to multi-celled and are of varied shapes.

Spores of some fungi, especially conidia and ascospores possess distinctive features leading to their identification and categorization with the extant forms. Fossil spores can be generally assigned to a natural class system of Phycomycetes, Ascomycetes or Basidiomycetes if the diagnostic morphological features are observable. Some fossil materials are assigned to the class Fungi-Imperfecti where spores or isolated structures (conidia, pycnidia or other sporangia, or isolated mycelia) are of exclusive morphology.

Table 1. Classification and diagnostic characters of fossil fungal spores

Fungal spore stratigraphy

Although most of the fungal spores are long ranging and do not bear any stratigraphical significance, but some are morphologically very distinct and have restricted range in geological time. Applicability of fungal spores has, therefore, increased with the record of such characteristic spores (Kalgutkar and Jansonius, 2000). Graham (1962) was amongst the pioneers to suggest the possibility of using fungal spores for supplementing age determinations in palynological studies. According to Elsik (1970) although variety of fungal spores are recorded from Mesozoic strata world over, their morphological complexity and frequency increases in Cenozoic. He noted that Fusiformisporites and similar longitudinally ribbed forms appear to be restricted to the Cenozoic. Elsik (op. cit.) further observed that fossil fungal spores described as Exesisporites which resemble with extant Hypoxylon type are more frequently recorded in Neogene sediments. Ramanujam (1982) opined that overall diversity in morphology of fungal spore was attained by late Cretaceous and Early Tertiary. While evaluating the stratigraphic potential of fungal remains in Indian sequences, he further observed that spores with relatively simpler morphology were recorded from early Mesozoic strata but in younger sediments ornamented spores with complex morphology were recorded. Kalgutkar and Jansonius (2000) while summarizing the stratigraphic significance of fossil fungal forms mentioned that as Pesavis tagluensis have a distinct morphology hence it is a stratigraphic mar...

Table of contents

• Cover
• Half Title
• Series Page
• Title Page
• Copyright Page
• Table of Contents
• List of Contributors
• Preface
• 1. Fungi from Palaeoenvironments: Their Role in Environmental Interpretations
• 2. Fungi in the Air—Aeromycology: An Overview
• 3. Fungi in Saline Water Bodies with Special Attention to the Hypersaline Dead Sea Mycobiota
• 4. Filamentous Fungi in the Marine Environment: Chemical Ecology
• 5. The Genus Achlya from Alkaline and Sewage Polluted Aquatic Environment
• 6. Keratinolytic and Keratinophilic Fungi in Sewage Sludge: Factors Influencing their Occurrence
• 7. Fungi in Snow Environments: Psychrophilic Molds—A Group of Pathogens Affecting Plants under Snow
• 8. Fungi from High Nitrogen Environments—Ammonia Fungi: Eco-Physiological Aspects
• 9. Prospecting for Novel Enzyme Activities and Their Genes in Filamentous Fungi from Extreme Environments
• 10. The Cuckoo Fungus ‘Termite ball’ Mimicking Termite Eggs: A Novel Insect-fungal Association
• 11. The Hallucinogenic Mushrooms: Diversity, Traditions, Use and Abuse with Special Reference to the Genus Psilocybe
• 12. Environmental Impacts on Fatty Acid Composition of Fungal Membranes
• 13. Microsporum canis—A Pathogen of Cats and Its Control Through Environmental Management: A Review
• 14. Thermophilic Molds in Environmental Management
• Subject Index
• Genus & Species Index