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About this book

This two-volume edited book highlights and reviews the potential of the fossil record to calibrate the origin and evolution of parasitism, and the techniques to understand the development of parasite-host associations and their relationships with environmental and ecological changes. The book deploys a broad and comprehensive approach, aimed at understanding the origins and developments of various parasite groups, in order to provide a wider evolutionary picture of parasitism as part of biodiversity. This is in contrast to most contributions by parasitologists in the literature that focus on circular lines of evidence, such as extrapolating from current host associations or distributions, to estimate constraints on the timing of the origin and evolution of various parasite groups. This approach is narrow and fails to provide the wider evolutionary picture of parasitism on, and as part of, biodiversity.

Volume one focuses on identifying parasitism in the fossil record, and sheds light on the distribution and ecological importance of parasite-host interactions over time. In order to better understand the evolutionary history of parasites and their relationship with changes in the environment, emphasis is given to viruses, bacteria, protists and multicellular eukaryotes as parasites. Particular attention is given to fungi and metazoans such as bivalves, cnidarians, crustaceans, gastropods, helminths, insects, mites and ticks as parasites. Researchers, specifically evolutionary (paleo)biologists and parasitologists, interested in the evolutionary history of parasite-host interactions as well as students studying parasitism will find this book appealing.

Table of Contents

Frontmatter

Chapter 1. Parasites of Fossil Vertebrates: What We Know and What Can We Expect from the Fossil Record?

Abstract
Parasites are ubiquitous in extant ecosystems and vertebrate animals often harbour rich parasite communities. However, the geological record of parasites is extremely sparse as their very nature means they are rarely fossilised. The few fossil parasites which have been described have provided interesting insights into the evolution of various parasite taxa, and the development of technology such as high-resolution computed tomography has made detecting signs of parasitism in the fossil record more practical. In this chapter, I will provide an overview of vertebrate-infecting macroparasites which have been described from fossils, and compare those fossil forms with their extant counterparts. I will also discuss what those fossils can tell us about the evolution of parasitism and the ecology of their hosts, the type of parasite fossils which may be associated with fossil vertebrates, and suggest some future research directions which combine aspects of palaeontology, ecology, and parasitology.
Tommy L. F. Leung

Chapter 2. Fossil Record of Viruses, Parasitic Bacteria and Parasitic Protozoa

Abstract
Fossil evidence of ancient pathogens is rare and limited mostly to specimens associated with arthropod vectors in amber. In various fossil vectors is evidence of cytoplasmic and nuclear polyhedrosis viruses, pathogenic spirochetes, rickettsia, actinomycetes and protozoa. Also present in amber are examples of fossil virus-like tumors and indirect evidence of iridoviruses, polydnaviruses, pathogenic bacteria and protozoans. Many of these pathogens resemble those being transmitted today to a range of vertebrate hosts by arthropod vectors. Based on these findings, it is clear that invertebrate and vertebrate viruses, as well as a range of pathogenic bacteria and protozoa, were well established by the mid-Cretaceous.
George Poinar

Chapter 3. Fungi as Parasites: A Conspectus of the Fossil Record

Abstract
Fungal parasites are important drivers in ecosystem dynamics today that can have far-reaching effects on the performance and community structure of other organisms. Knowledge of the fossil record and evolution of fungal parasitism is therefore a key component of our understanding of the complexity and functioning of ancient ecosystems. However, the fossil record of fungi as parasites remains exceedingly incomplete for several reasons. This chapter provides selected fossil examples of (putative) fungal parasites in association with land plants, algae, other fungi, and animals, and elucidates the inherent problems that often render interpretation of even the most exquisite fungal fossils difficult. Of all the potential levels of fungal interaction, parasitism is perhaps the most difficult to demonstrate in the fossil record. Different lines of evidence obtained from both the host and fungus are required to safely discriminate parasitic fungi from saprotrophs and even mutualists when examined in fossils.
Carla J. Harper, Michael Krings

Chapter 4. Evolution, Origins and Diversification of Parasitic Cnidarians

Abstract
Parasitism has evolved in cnidarians on multiple occasions but only one clade—the Myxozoa—has undergone substantial radiation. We briefly review minor parasitic clades that exploit pelagic hosts and then focus on the comparative biology and evolution of the highly speciose Myxozoa and its monotypic sister taxon, Polypodium hydriforme, which collectively form the Endocnidozoa. Cnidarian features that may have facilitated the evolution of endoparasitism are highlighted before considering endocnidozoan origins, life cycle evolution and potential early hosts. We review the fossil evidence and evaluate existing inferences based on molecular clock and cophylogenetic analyses. Finally, we consider patterns of adaptation and diversification and stress how poor sampling might preclude adequate understanding of endocnidozoan diversity.
Beth Okamura, Alexander Gruhl

Chapter 5. Evolutionary History of Bivalves as Parasites

Abstract
Bivalves commonly associate with other organisms, however, examples of true parasitic associations are described only for members of the marine superfamily Galeommatoidea (two species of approximately 500 known species, facultative parasitism) and the larvae of members of the freshwater order Unionida (almost all of 958 known species, obligate parasitism). The evolution toward such a close relationship required establishing a close association with the host’s body, resulting in being enclosed within its tissues. Clear adaptations to the host species are observed in both groups. Most galeommatoideans live in soft sediments and are associated with other benthic organisms or their burrows—settlement in a burrow or on/within the host’s body protects these little bivalves, while life activity of the host possibly ensures oxygenated water currents with a food source for the bivalve. However, a few recent examples of bivalve settlement within the body cavity of crabs (believed as accidental, nevertheless bivalves feed in the crab's hemocoel), or in the oesophagus of holothurians (common, presumably nutrition from the host is possible) indicate possible pathways for an evolutionary transition from free- or commensal-living to a parasitic lifestyle. Unionoids, large freshwater bivalves, are characterized by their tiny larvae that parasitize fish. This close relationship primarily benefits bivalves through enhanced dispersal abilities, but fish tissues may also serve as a source of nutrients for the larvae. Parasitic association likely established when close and common contact of both associates could happen, thus one may hypothesize a fish that lived close to the bottom of lakes and rivers (including durophagous species) as a likely host at the beginning of their co-evolution. Accidental contact of the larvae with the body of fishes (during predation on bivalves or caused by anti-sinking mucous or the larval threads tangled with fish) could result in increased bivalve dispersal. Subsequently, firmer attachment on fish tissues was acquired, followed by encapsulation of the larva within the host epithelium. This might have allowed for the feeding on host tissues, but required developing resistance to the host’s immune system, which might have further strengthened their association.
Aleksandra Skawina

Chapter 6. GastropodsMolluscaas parasitesGastropodaParasitic gastropods as Parasites and Carnivorous Grazers: A Major Guild in Marine Ecosystems

Abstract
Parasitism and similar life styles such as carnivorous grazing or mucus feeding without killing the prey are important in marine gastropods. Some of the most diverse living gastropod families have this feeding behavior. Taxonomic uniformitarianism is the most important tool to infer parasitism or similar life styles in fossil gastropods. The extant family groups in question (Eulimidae, Epitoniidae, Pyramidellidae, Architectonicidae, Coralliophilinae, Ovulidae, Cerithiopsidae and Triphoridae) originate mostly in the Late Cretaceous (Cerithiopsidae in the Middle Jurassic) and Paleocene. They are performing an ongoing adaptive radiation and some of the mentioned families belong to the most diverse gastropod groups forming a considerable part of marine ecosystems regarding species richness and relative abundance. At the same time, origination and radiation of the carnivorous, commonly predatory Neogastropoda took place. This points to a trophic revolution in Gastropoda that forms an important aspect of the Mesozoic Marine Revolution. Most modern parasitic gastropods are small, high-spired, show high diversity and low disparity within families and belong to Apogastropoda. By analogy, some extinct gastropod families which show the same properties might have lived parasitic too (e.g., Pseudozygopleuridae, Zygopleuridae, Meekospiridae, Donaldinidae). However, this will remain speculative to a large degree until direct host associations are found. Direct evidence for parasitism is exceptional with the Palaeozoic platyceratid/crinoid interaction being one of the best studied examples. In Gastropoda, functional shell morphology may help to identify parasitism in the fossil record but this field is scarcely studied.
Alexander Nützel

Chapter 7. Fossil Constraints on the Timescale of Parasitic Helminth Evolution

Abstract
The fossil record of parasitic helminths is often stated to be severely limited. Many studies have therefore used host constraints to constrain molecular divergence time estimates of helminths. Here we review direct fossil evidence for several of these parasitic lineages belong to various phyla (Acanthocephala, Annelida, Arthropoda, Nematoda, Nematomorpha, Platyhelminthes). Our compilation shows that the fossil record of soft-bodied helminths is patchy, but more diverse than commonly assumed. The fossil record provides evidence that ectoparasitic helminths (e.g., worm-like pentastomid arthropods) have been around since the early Paleozoic, while endoparasitic helminths (cestodes, nematodes) arose at least during, or possibly even before the late Paleozoic. Nematode lineages parasitizing terrestrial plant and animal hosts have been in existence at least since the Devonian and Triassic, respectively. All major phyla (Acanthocephala, Annelida, Platyhelminthes, Nematoda, Nematomorpha) had evolved endoparasitic lineages at least since the Mesozoic. Interestingly, although parasitism is considered derived within Metazoa, the oldest evidence for Nematoda and Platyhelminthes includes body fossils of parasitic representatives. Furthermore, the oldest fossil evidence of these parasitic lineages often falls within molecular divergence times based on host co-evolution suggesting the fossil record of helminths themselves might be just as good or at least complementary (and less circular in justification) to calibration based on host associations. Data also provide evidence for obvious host switches or extinctions, which cautions against models of pure co-divergence where use of host calibrations to constrain divergence time estimates may be considered.
Kenneth De Baets, Paula Dentzien-Dias, G. William M. Harrison, D. Timothy J. Littlewood, Luke A. Parry

Chapter 8. Thorny-Headed Worms (Acanthocephala): Jaw-Less Members of Jaw-Bearing Worms That Parasitize Jawed Arthropods and Jawed Vertebrates

Abstract
Stem-acanthocephalans in the millimeter range might already have parasitized mandibulates in the Cambrian, while larger body sizes presumably evolved along with the upward-inclusion of gnathostome hosts. The characteristic morphology of modern acanthocephalans including the mostly hooked attachment organ (proboscis) should have emerged in the same context. Due to their rigidity, acanthocephalan hooks and copulatory caps are candidates for fossilization, but soft-tissue preservation might also have occurred under exceptional circumstances. Nonetheless, eggs represent the only ancient remains assigned to acanthocephalans to date. These were mostly retrieved from dried mammalian coprolites of up to ca. 12,000 years old. However, the recent discovery of eggs in a coprolite from the Upper Cretaceous illustrates that acanthocephalan eggs can also occur in fossilized remains. These and other aspects of acanthocephalan preservation, morphology, phylogeny, evolution, and pathogenicity are discussed in the present chapter that additionally includes a reflection of why Cambroclavida unlikely have an acanthocephalan origin.
Holger Herlyn

Chapter 9. Chelicerates as Parasites

Abstract
Among Chelicerata, larval instars of sea spiders (Pycnogonida) can be parasitic. The oldest putative sea spider from the Cambrian ‘Orsten’ is immature and resembles comparable instars of modern species with a parasitic phase to their life cycle. All other parasitic chelicerates are mites, with several examples in both the Acariformes and Parasitiformes clades. Fossils revealing parasitic behaviour, or belonging to purely parasitic clades, come from various amber sources from the mid-Cretaceous onwards. From Acariformes there are records of Parasitengona, Myobiidae, Pterygosomatoidea, Resinacaridae, Acarophenacidae, Pyemotidae and Apotomelidae. Parasitiformes is represented by several ticks (Ixodida) and potentially Laelapidae from the Mesostigmata. Parasitism appears to have evolved independently within mites on several occasions. Possible transitions to this lifestyle via nest associations and/or phoresy are discussed. Arachnids as victims of parasites include amber records of nematode worms (Mermithidae), erythraeid mites (Erythraeidae), mantid flies (Neuroptera: Mantispidae), ichneumon wasps (Hymenoptera: Ichneumonidae) and spider flies (Diptera: Acroceridae).
Jason A. Dunlop

Chapter 10. Evolutionary History of Crustaceans as Parasites

Abstract
Modern crustaceans are extremely diverse, not only in their morphologies, but also in their life styles. It is therefore not surprising that parasitism evolved in various lineages of Eucrustacea independently, in groups such as amphipodan, isopodan and copepodan crustaceans, but also barnacles and fish lice. Parasitic crustaceans have become specialized to many different host species and show a wide variety of attachment and feeding specializations. Among the parasitic crustaceans, different groups are especially interesting to study for reconstructing the evolution of parasitism within this group. This chapter summarizes the modern aspects, evolutionary history and fossil record of parasitic crustacean groups. By reviewing the parasitic crustaceans with emphasis on their fossil record, this chapter aims to improve our understanding of parasitism in general.
Joachim T. Haug, Carolin Haug, Christina Nagler

Chapter 11. The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution

Abstract
Insect parasites and parasitoids are a major component of terrestrial food webs. For parasitoids, categorization is whether feeding activity is located inside or outside its host, if the host is immobilized or allowed to grow, and if the feeding is done by one or many conspecific or heterospecific individuals, and other features. Fossil evidence for parasitism and parasitoidism consists of taxonomic affiliation, morphology, gut contents, coprolites, tissue damage and trace fossils. Ten hemimetabolous and holometabolous orders of insects developed the parasite condition whereas seven orders of holometabolous insects evolved the parasitoid life habit. Modern terrestrial food webs are important for understanding the Mid Mesozoic Parasitoid Revolution. The MMPR began in late Early Jurassic (Phase 1), in which bottom-to-top regulation of terrestrial food webs dominated by inefficient clades of predators were replaced by top-to-bottom control by trophically more efficient parasitoid clades. The MMPR became consolidated in Phase 2 by the end of the Early Cretaceous. These clades later expanded (phases 3 and 4) as parasitoids became significant ecological elements in terrestrial food webs. Bottom-to-top food webs explained by the resource concentration hypothesis characterize pre-MMPR time. During phases 1 and 2 of MMPR (Middle Jurassic to Early Cretaceous), a shift ensued toward top-to-down food webs, explained by the trophic cascade hypothesis, exemplified by hymenopteran parasitoid clades Stephanoidea and Evanioidea. Clade-specific innovations spurring the MMPR included long, flexible ovipositors (wasps), host seeking, triungulin and planidium larvae (mantispids, beetles, twisted-wing parasites, flies), and extrudable, telescoped ovipositors (flies). After the MMPR, in phases 3 and 4 (Late Cretaceous to Recent), parasitoids increased in taxonomic diversity, becoming integrated into food webs that continue to the present day.
Conrad C. Labandeira, Longfeng Li

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