Paleoparasitology
Encyclopedia
Paleoparasitology is the study of parasite
s from the past, and their interactions with hosts and vectors; it is a subfield of Paleontology
, the study of living organisms from the past. Some authors define this term more narrowly, as "Paleoparasitology is the study of parasites in archaeological material." (p. 103) K.J. Reinhard suggests that the term "archaeoparasitology
" be applied to "... all parasitological remains excavated from archaeological contexts ... derived from human activity" and that "the term 'paleoparasitology' be applied to studies of nonhuman, paleontological material." (p. 233) This article follows Reinhard's suggestion and discusses the protozoa
n and animal parasites of non-human animals and plants from the past, while those from humans and our hominid ancestors are covered in archaeoparasitology
.
tissues, coprolite
s (fossilised dung) from mammals or dinosaurs, fossil
s, and amber inclusions. Hair, skins, and feathers also yield ectoparasite remains. Some archaeological artifacts document the presence of animal parasites. One example is the depiction of what appear to be mites in the ear of a "hyaena-like" animal in a tomb painting from ancient Thebes
.
Some parasites leave marks or traces (ichnofossils) on host remains, which persist in the fossil record in the absence of structural remains of the parasite. Parasitic ichnofossils include plant remains which exhibit characteristic signs of parasitic insect infestation, such as gall
s or leaf mines
and certain anomalies seen in invertebrate endoskeletal remains.
Plant and animal parasites have been found in samples from a broad spectrum of geological periods, including the Holocene
(samples over 10,000 years old), Pleistocene
(over 550,000 years old), Eocene
(over 44 million years old), Cretaceous
(over 100 million years) and even Lower Cambrian (over 500 million years).
, mutualism, and commensalism
. Demonstration of true parasitism between existing species typically involves observing the harmful effects of parasites on a presumed host. Experimental infection of the presumed host, followed by recovery of viable
parasites from that host also supports any claim of true parasitism. Obviously such experiments are not possible with specimens of extinct organisms found in paleontological contexts.
Assumptions of true parasitism in paleontological settings which are based on analogy to known present-day parasitic relationships may not be valid, due to host-specificity. For example, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense are both devastating human parasites, but the related subspecies Trypanosoma brucei brucei will infect a number of animal hosts, but cannot even survive in the human blood stream, much less reproduce and infect a human host. So a related (or unidentifiable) species of Trypanosoma found in a paleontological or archaeological context may not be a true human parasite, even though it appears identical (or very similar) to the modern parasitic forms.
The most convincing evidence of paleoparasitism is obtained when a presumed parasite is found in direct association with its presumed host, in a context that is consistent with known host-parasite associations. Some examples include helminths caught in amber in the process of escaping from the body of an insect, lice found in the fur of guinea pig mummies, protozoans in the alimentary canal of flies in amber, nematode larvae
found embedded in animal coprolites, and a mite caught in amber in the process of apparently feeding on a spider.
Fossil organisms which are related to present-day parasites often possess the morphological
features associated with a parasitic lifestyle, such as blood-feeding mouthparts. So fossil ticks and hematophagous
insects are generally assumed to be ectoparasites, even when their remains are found in the absence of a host.
The presence of structures resembling leaf miner trails in leaf fossils provide indirect evidence of parasitism, even if remains of the parasite are not recovered. The dramatic tissue aberrations seen in present-day plant gall
s and gall-like structures in some invertebrates are direct physiological reactions to the presence of either metazoan
parasites or microbial pathogens. Similar structures seen in fossil plant and invertebrate remains are often interpreted as evidence of paleoparasitism.
Host-parasite interactions today are often exploited by other species, and similar examples have been found in the fossil record of plant galls and leaf mines. For example, there are species of wasps, called inquilines, which are unable to induce their own plant galls, so they simply take up residence in the galls that are made by other wasps. Another example is the predation
of plant galls or leaf mines, to eat the trapped insect larva inside the gall or mine.
In some cases, presumed host-parasite relationships of the past seem quite different from those known in the present, such as a fly which appears to be a parasite of a mite
Paleoparasitological studies have also provided insight into questions outside the realm of parasitology. Examples include the migration and phylogeography of marine mammal hosts, the identity of domestic animal bones based on the known hosts of parasite remains found at the site, and the possible role of climatic changes on animal host genetic diversity.
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
s from the past, and their interactions with hosts and vectors; it is a subfield of Paleontology
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
, the study of living organisms from the past. Some authors define this term more narrowly, as "Paleoparasitology is the study of parasites in archaeological material." (p. 103) K.J. Reinhard suggests that the term "archaeoparasitology
Archaeoparasitology
Archaeoparasitology, a multi-disciplinary field within paleopathology, is the study of parasites in archaeological contexts. It includes studies of the protozoan and metazoan parasites of humans in the past, as well as parasites which may have affected past human societies, such as those...
" be applied to "... all parasitological remains excavated from archaeological contexts ... derived from human activity" and that "the term 'paleoparasitology' be applied to studies of nonhuman, paleontological material." (p. 233) This article follows Reinhard's suggestion and discusses the protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
n and animal parasites of non-human animals and plants from the past, while those from humans and our hominid ancestors are covered in archaeoparasitology
Archaeoparasitology
Archaeoparasitology, a multi-disciplinary field within paleopathology, is the study of parasites in archaeological contexts. It includes studies of the protozoan and metazoan parasites of humans in the past, as well as parasites which may have affected past human societies, such as those...
.
Sources of material
The primary sources of paleoparasitological material include mummifiedMummy
A mummy is a body, human or animal, whose skin and organs have been preserved by either intentional or incidental exposure to chemicals, extreme coldness , very low humidity, or lack of air when bodies are submerged in bogs, so that the recovered body will not decay further if kept in cool and dry...
tissues, coprolite
Coprolite
A coprolite is fossilized animal dung. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour rather than morphology. The name is derived from the Greek words κοπρος / kopros meaning 'dung' and λιθος / lithos meaning 'stone'. They...
s (fossilised dung) from mammals or dinosaurs, fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s, and amber inclusions. Hair, skins, and feathers also yield ectoparasite remains. Some archaeological artifacts document the presence of animal parasites. One example is the depiction of what appear to be mites in the ear of a "hyaena-like" animal in a tomb painting from ancient Thebes
Ancient Thebes (Boeotia)
See Thebes, Greece for the modern city built on the ancient ruins.Ancient Thebes was a Boeotian city-state , situated to the north of the Cithaeron range, which divides Boeotia from Attica, and on the southern edge of the Boeotian plain...
.
Some parasites leave marks or traces (ichnofossils) on host remains, which persist in the fossil record in the absence of structural remains of the parasite. Parasitic ichnofossils include plant remains which exhibit characteristic signs of parasitic insect infestation, such as gall
Gall
Galls or cecidia are outgrowths on the surface of lifeforms caused by invasion by other lifeforms, such as parasites or bacterial infection. Plant galls are abnormal outgrowths of plant tissues and can be caused by various parasites, from fungi and bacteria, to insects and mites...
s or leaf mines
Leaf miner
Leaf miner is a term used to describe the larvae of many different species of insect which live in and eat the leaf tissue of plants. The vast majority of leaf-mining insects are moths , sawflies and flies , though some beetles and wasps also exhibit this behavior.Like Woodboring beetles, leaf...
and certain anomalies seen in invertebrate endoskeletal remains.
Plant and animal parasites have been found in samples from a broad spectrum of geological periods, including the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
(samples over 10,000 years old), Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
(over 550,000 years old), Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
(over 44 million years old), Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
(over 100 million years) and even Lower Cambrian (over 500 million years).
Evidence of parasitism
One of the most daunting tasks involved in studying parasitic relationships from the past is supporting the assertion that the relationship between two organisms is indeed parasitic. Organisms living in "close association" with each other may exhibit one of several different types of trophic relationships, such as parasitismParasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
, mutualism, and commensalism
Commensalism
In ecology, commensalism is a class of relationship between two organisms where one organism benefits but the other is neutral...
. Demonstration of true parasitism between existing species typically involves observing the harmful effects of parasites on a presumed host. Experimental infection of the presumed host, followed by recovery of viable
Viability
Viable or viability is the ability of a thing to maintain itself or recover its potentialities.Viable or viability may also refer to:...
parasites from that host also supports any claim of true parasitism. Obviously such experiments are not possible with specimens of extinct organisms found in paleontological contexts.
Assumptions of true parasitism in paleontological settings which are based on analogy to known present-day parasitic relationships may not be valid, due to host-specificity. For example, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense are both devastating human parasites, but the related subspecies Trypanosoma brucei brucei will infect a number of animal hosts, but cannot even survive in the human blood stream, much less reproduce and infect a human host. So a related (or unidentifiable) species of Trypanosoma found in a paleontological or archaeological context may not be a true human parasite, even though it appears identical (or very similar) to the modern parasitic forms.
The most convincing evidence of paleoparasitism is obtained when a presumed parasite is found in direct association with its presumed host, in a context that is consistent with known host-parasite associations. Some examples include helminths caught in amber in the process of escaping from the body of an insect, lice found in the fur of guinea pig mummies, protozoans in the alimentary canal of flies in amber, nematode larvae
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
found embedded in animal coprolites, and a mite caught in amber in the process of apparently feeding on a spider.
Fossil organisms which are related to present-day parasites often possess the morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
features associated with a parasitic lifestyle, such as blood-feeding mouthparts. So fossil ticks and hematophagous
Hematophagy
Hematophagy is the practice of certain animals of feeding on blood...
insects are generally assumed to be ectoparasites, even when their remains are found in the absence of a host.
The presence of structures resembling leaf miner trails in leaf fossils provide indirect evidence of parasitism, even if remains of the parasite are not recovered. The dramatic tissue aberrations seen in present-day plant gall
Gall
Galls or cecidia are outgrowths on the surface of lifeforms caused by invasion by other lifeforms, such as parasites or bacterial infection. Plant galls are abnormal outgrowths of plant tissues and can be caused by various parasites, from fungi and bacteria, to insects and mites...
s and gall-like structures in some invertebrates are direct physiological reactions to the presence of either metazoan
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
parasites or microbial pathogens. Similar structures seen in fossil plant and invertebrate remains are often interpreted as evidence of paleoparasitism.
Host-parasite interactions today are often exploited by other species, and similar examples have been found in the fossil record of plant galls and leaf mines. For example, there are species of wasps, called inquilines, which are unable to induce their own plant galls, so they simply take up residence in the galls that are made by other wasps. Another example is the predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
of plant galls or leaf mines, to eat the trapped insect larva inside the gall or mine.
Knowledge gained from ancient animal and plant parasites
Studies of parasite remains and traces from the past have yielded a vast catalog of ancient host-parasite associations. Genetic sequence data obtained directly from ancient animal parasites, and inferences of past relationships based on genetic sequences of existing parasite groups are also being applied to paleoparasitological questions. Data obtained by all of these methods are constantly improving our understanding of the origin and evolution of the parasites themselves and their vectors, and of the host-parasite and vector-parasite associations.In some cases, presumed host-parasite relationships of the past seem quite different from those known in the present, such as a fly which appears to be a parasite of a mite
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
Paleoparasitological studies have also provided insight into questions outside the realm of parasitology. Examples include the migration and phylogeography of marine mammal hosts, the identity of domestic animal bones based on the known hosts of parasite remains found at the site, and the possible role of climatic changes on animal host genetic diversity.