Paper : 08 Biology of Module : 02 Animal Association and Host-parasite interaction, Part 2

Development Team

Principal Investigator: Prof. Neeta Sehgal Department of Zoology, University of Delhi

Co-Principal Investigator: Prof. D.K. Singh Department of Zoology, University of Delhi

Paper Coordinator: Dr. Pawan Malhotra ICGEB, New Delhi

Content Writer: Dr.Haren Ram Chiary Kirori Mal College, University of Delhi

Content Reviewer: Prof. Rajagopal Raman Department of Zoology, University of Delhi

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Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2

Description of Module

Subject Name ZOOLOGY

Paper Name Biology of Parasitism: Zool 008

Module Name/Title Animal Association and Host-parasite interaction.

Module Id M02: Animal Association and Host-parasite interaction. Part 2

Keywords Antibiosis, Ammensalism, Interference , Exploitation competition, Competitive Exclusion Principle, Character Displacement, and Parasitism, Host -Parasite Interaction, Disease and parasitism, Social parasitism.

CONTENTS 1. Learning Objective 2. Introduction 3. Negative interactions 3.1 Antibiosis 3.2 Synnecrosis 3.3 Ammensalism 3.4 Competition 3.4.1. Types of Competition on mechanism basis 3.4.1.a. Interference competition 3.4.1.b. Exploitation competition 3.4.1.c. Apparent competition 3.4.2. Types of Competition on species basis 3.4.2.a. Intraspecific competition 3.4.2.b. Interspecific competition i. Competitive Exclusion Principle ii. Character Displacement iii. Partitioning 2

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4. Predation and Parasitism 5. Host -Parasite Interaction 5.1 Parasitic characteristics 5.2 Types of parasites 5.3 Host as 5.4 Disease and parasitism 5.5 Social parasitism 6. Summary

1. Learning Outcomes

After studying this module, you shall be able to

 Understand the importance of negative interactions in the regulation of structure.  Learn how negative interactions help in the process of colonization.  Know different types of negative interactions in the with examples and different theories.  Evaluate the host-parasite interactions.  Understand the importance of parasites in association with diseases.

2. Introduction

Ecology is a science of communities, giving new directions to the interrelationship of animals and . V.E. Shelford and F.E. Clements, 1939, tied and animal on one common ground which was earlier considered as separate fields of ecology. “Bio-ecology” is the term that narrowed this division and explains that the interacting components of broad biotic communities are plants and animals that together covered the field of ecology. The organisation of community may be influenced by interactions among its member species. Hence, the goal is to summarize and understand the complex ecological interrelationships of many components forming the stable community structure. Either positive or negative, interactions among population have a substantial role in shaping the structure of a community and its stability. Among negative or harmful interactions, competitive exclusions have been considered as a cornerstone of community structure since 1859 when Darwin suggested interspecific competition as hallmark of population dynamic regulators. Many other ecologists have also pointed out the role of detrimental relationships in proper allocation of resources, 3

Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2

regulating distribution of species, niche segregation thereby shaping community organisation. Among competitive relationships, have enhanced influence on community by affecting one or more trophic levels. R. MacArthur (1955) stated that simple communities are less stable than those with complex food webs. Predation and parasitism are an integral part of natural communities.

3. Negative Interaction

Population is constantly increasing leading to crowded living space, where more and more members share food, making it a limiting factor, thereby increasing social stress. An will respond to this population increase and stress by attempting to obtain the resources that are inadequate to support all the individuals seeking it. These interactions will lead to detrimental effects and competition among the interacting species. Clarke, 1954, cited a relationship between individuals where both are harmed and termed this interaction as “antagonism”. These interactions are briefly discussed in this chapter.

3.1 Antibiosis

Antibiosis refers to the inhibition of one species by another through the secretion of some chemical substances from their metabolic pathways. Neither population is benefitted; rather it is a one sided nebulous relationship where one organism had a detrimental effect on another by the production of or alleleochemical agents. As an example, a chemical has been secreted from the black walnut roots that harm neighbouring plants (Figure 1A). Microbial population provides good examples of antibiosis. Burkholder, 1952, cited that 50% population of actinomycetes and lichens inhibits molds and . Blue green algae and Microcystis in ponds causes “algal bloom” and death of cattle and fishes by producing toxins like hydroxylamine (figure.1B). Hypersensitive reactions are the phenomena included in antibiosis, which involves the relationship between pathogenic harmful to one or both.

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Figure1. (A) Black walnut tree showing antibiosis, (B) Algal blooms.

3.2 Synnecrosis

Synnecrosis is a rarely used mutually detrimental interaction resulting in negative effects to both the interacting species. Negatively selected by the evolution, it’s a short-lived condition ultimately causing death of interacting species as in case of predation. Bees and their prey are best examples to explain this relationship where bees die after stinging to protect the hive, inflicting pain to the prey/victim (figure.2).

Figure2. Bees and their prey are good example of synnecrosis. 5

Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2

3.3 Ammensalism

Ammensalism is a relationship where a species inflicts detrimental effects to another species without any benefit or harm to itself. As in case of grazing animals and grasslands, grass has no effects on the grazing cattle’s or animal’s hoof while the grass is influenced by being crushed by the animals (figure.3A). Another example is Elephants stepping on ants do not affect Elephant but leads to ant death or when Elephant walks on grasses it leads to leveling of brush that does not benefit the elephant but causes harm to the grasses (figure.3B).

Figure3. (A) grazing cattle, (B) Elephants

3.4 Competition

Competition, in ecology, is a class of relationship in which the fitness of one organism is influenced / lowered by the presence of another. Population composed of of its own kind of species

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sharing very similar requirement of resources for growth and reproduction may exceed the immediate supply of those resources leading to competition between the associated organisms.

Competition can happen in both direct and indirect ways and is not always a straightforward interaction. This type of interaction is usually facilitated by the associated species sharing common amenities such as nutrients, water and territory and in trying to obtain it. When the resources become limited or inadequate to support all individuals seeking it, the interactions become more detrimental. The magnitude of competition depends on many interacting a-biotic factors and biotic factors in the same ecosystem that affects the structure of the community. Two types of resources can act as limiting factors (a) raw materials like organic nutrients and water, which comes under and inorganic food, light and water in , (b) habitat to grow hide, from predators etc.

Competition is an area of involving members of same species as well as members of different species, hence classified either on the basis of species specific competition or on the basis of mechanism involving direct or indirect competition (figure.4).

Figure4. Cartoon illustrating the types of competition

3.4. 1. Types of competition on thebasis of mechanism

Birch, 1957 defined two different types of competition (a) Resource competition also called exploitative or scramble competition. This type of interactions occurs when a number of organisms of the same species or different species utilize similar requirement of resources that are in short supply; (b) Interference competition also termed as contest competition, occurs when the organisms harm one another and try to obtain resources not even in short supply. Although, an exact

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mechanism is not known, we can generally divide the mechanisms into direct and indirect basis where few terms can describe equally interspecific and intraspecific competitions.

3.4.1.a. Interference competition

Interference involves direct competition between interacting individuals via aggression behaviour etc. An individual directly interfering the physical establishment of another individual in the portion of habitat and where resources are not even limited. An example of direct competition is when male hartebeest ferociously defend their territories (figure.5A). Another example of direct interference competition for territories, mates or food are competing Flamingos (figure.5B).

Figure.5. (A) Hartebeest and (B) Flamingos defending their territories.

Allelopathy involves the secretion of chemical substances inhibiting the growth of other organismand thus is a particular form of direct competition. It’s a uni-directional chemical interaction where one interacting individual secretes allelochemical agents. Casuarina equisetifolia and Allocasuarina spp (leaf litter) have strong allelopathic properties evidenced by the suppression of understory plants germination (figure.6).

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Figure.6. C. Equisetifolia subsp. incana

3.4.1.b. Exploitation competition

Exploitative or contest competition is the indirect competition between species sharing common limiting resources (support, shelter or food) where one species reduces the availability of resources to another resulting in reduced growth, survival and reproduction. For example, contest competition has been experimentally proven between the juveniles of a wolf spider species, Schizocosaocreata. Food is the limiting factor for the increasing density of juvenile spiders leading to an indirect competition for food between them thereby reducing the fitness of young ones (figure.7).

Figure.7. Juveniles attached to the abdomen of mother Wolf spider

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3.4.1.c. Apparent competition

An indirect relationship between two prey organisms predated by the common organism called predator. The increase of one prey organism decreases the number of another prey organism because that increase helps in the survival or increase in number of the common predator which in turn predate more on the second prey. Therefore, one prey population indirectly through common predator detrimentally affects second prey population. For example, an opportunistic predator, Mustela spp., the stoat in New Zealand leads to decline in population of native skinks (Oligosoma) when rabbits were introduced into New Zealand. Immigration of ferrets to that area is a result of introduced rabbits (figure.8). Skinks are eaten by stoats and have large devastating effect on skinks population.

Figure.8. Stoats predating rabbits

3.4.2. Types of competition on the basis of species

On the basis of type of interacting organisms whether belonging to same species or different species, broadly two types of competition exist in biology.

3.4.2.a. Intraspecific competition

Competition may occur among members of same population competing for the same type of resources in an ecosystem. In more relevant terms this interaction explains resources availability situation rather than competition and also termed as scramble competition. For example, in Morocco at the pond of a Palace of Marrakech, Cyprinus carpio a species of freshwater fish, compete for food resources thus resulting into intraspecific competition (figure.9). Normally, intraspecific competition is more detrimental and fierce than interspecific competition. Exact mechanism may vary in different species but population are regulated by an important regulating density dependent factor. In population 10

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ecology, around a certain density of a population scramble competition leads to fluctuations. Competition may be defined as exploitation, where each individual/organism is affected by the amount of resources that remains after that resource has been exploited by others. Therefore, exploitation can only occur if resources in question are in limited supply. Competition takes the form of interference, where resources exploitation is prevented by one organism from another within a portion of the habitat. For instance, this is seen amongst animals that defend territories. Space can be seen as a resource in limited supply leading to reduction in survivorship, growth and reproduction.

Figure.9. Carp fishes in pond competing for food

3.4.2.b. Interspecific competition

Interspecific competition includes interference competition also called as contest competition. Interacting individuals of two different species competing for the limited resources leads to interspecific competition. For example, spotted hyena and male lion sharing same thereby compete with each (figure.10). In honour of the founders of the classical mathematical models of interspecific competition, the logistic model is called as Lotka-Volterra competition equations predicting four possible outcomes based on the assumptions of (a) fluctuation free stable environment, (b) instantaneous effects of competition, (c) migration is not important, (d) stable equilibrium leads to coexistence; (e) and the only important biological factor is competition. The possible outcomes of two interacting species occupying same space as competitors are:

1. Species A survive and competes with species B leading to its elimination. 2. Species B survive and competes with species A leading to its elimination.

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3. Both the species survive and eventually co-exist indefinitely. This happens when interspecific competition is less intense then intraspecific competition in both species. 4. Depending upon the ecological variables at one time, either species can survive leading to extinction of other species.

Figure.10. Interspecific competition between hyena and lion

i. Competitive Exclusion Principle: Complete competitors cannot exist

Georgy Gause was a Russian ecologist, who in 1934 explained competition as an outcome of co- existence of species. This classical theory is applicable in idealistic conditions i.e. continuous competition and stable environment. He proposed Gause’s principle, also known as Competitive Exclusion Principle, stating that no two species share same ecological niche. “Niche” is referred as the sum of requirements of resources and habitat needed by the species for the growth, survival and reproduction. Gause reasoned that if the ecological niche of two species overlaps or two species have identical ecological niche they would compete for exactly the same habitat and resources. His laboratory study on Protozoans involves Paramecium urelia and Paramecium caudatum competing with each other for the same resources. When these two Paramecium species are cultured separately, the population growth reaches to approximate logistic population density by volume. Protozoans when cultured together, one species, P. urelia, survives and P. caudatum was eliminated. However, is less closely fit into this model, but an example exists with two Tribolium species. T. confusum and T. castaneum are beetles that feeds on stored flour, were T. castaneum could survive and T. confusum died out.

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Figure.11: Population growth and competition of Paramecium culture. (A) and (B) separate cultures of two species. (C) Mixed culture of two species where P. caudatum dies out.

ii. Character Displacement

Strong interspecific competition is experienced by the competing species sharing similar traits leading to evolution of trait differences. The competitions in these species is more intense causing lower survival and reproduction rate than those species sharing different traits from competitors and therefore, contribute less to the future generation. Most common example is Darwin’s finches on Galapagos Islands (figure.12).

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Figure.12. Darwin’s finches on Galapagos Islands

iii. Resource Partitioning

Fluctuating environment and discontinuous competition leads to patchy distribution of population. Therefore, organisms respond differently to variable environment and different traits. Utilization of different resources leads to co-existence of species sharing same habitat. Each species exploits a portion of resources which is unusable to the other leading to differential resource utilization. For example, in stage one of figure. 13 a species of small birds (yellow) occupy the whole tree and forage for . In stage two larger intruder species of birds (red) competes for the same resources with the smaller birds. With time, in stage three, the larger compete for the more abundant middle part of the tree and dominates the smaller yellow birds. Both species thrive without competition as smaller species of yellow birds adapts to its new niche.

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Figure.13: Resource partitioning leads to co-existence of species. Stage (1) smaller yellow birds dominates the whole tree, (2) larger invasive species (red) introduced to the environment which competes with the yellow species and in stage (3) larger red species dominates smaller yellow species of bird for the middle portion of tree and both species thrive without competition

G.E Hutchinson, 1957 links niche to competition based on the Competition Exclusion Principle. He describes niches as a multidimensional hyperspace every coordinate of which corresponds to many physical and environmental variables in the life of species. He termed this space as hypervolume. The idealistic fundamental niche of the individual is the full hyper volume that a population can fill free from the interference of another population. The conditions under which an organism actually exists are its “realized niche”.

4. Predation and Parasitism

Predation and Parasitism are relations that positively affects one interacting species and detrimental to other. Killing and consumption of prey is an attribute to predation while parasitism involves small organisms called parasites which depend on another organism called host for their nutritional supply.

A predator-prey system involves higher tropic levels involving producers, and . A predator is a plant or animal that kills another species for food termed as “prey”. Predator use hunting tactics and special adaptations to catch and kill its prey. For example, Pantheratigrisa moyensis predating on blesbok (figure.14). Some examples of plant as predators

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(carnivores) exist in nature, for instance fungi like Dactylaria, Zoophagus, Dactylella etc. associate with animals for nutritional supply.

Figure.14:Pantheratigrisa moyensis predating on blesbok

Herbivory: A Plant- System. Interactions in which animals prey on plants leading to loss for the plants and benefits to animals is traditionally considered as Herbivory, which is a special kind of predation in contrast to . A plant-herbivore system is the interaction between herbivores predators and their plants. Herbivores are animals, for instance deer’s, giraffes etc., which predates on plants reducing plant fitness through defoliation, consumption of plant tissues and fruits and seeds removal (figure.15).

Figure.15: Deer’s exhibiting Herbivory

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Browsing and gazing, seeds and seedling destructions, and frequent consumption of plants as food create problems in the management of natural and artificial vegetation. Although herbivores detrimentally affect the plant fitness by reducing their ability of production and , plants have also evolved numerous defensive mechanisms against the herbivores including adjustment of timing of their reproduction according to their predators and perfecting chemical defences by producing secondary metabolites interfering negatively with the survival, growth and reproduction of the predator.

Herbivore- System: Cannibilism: An Intraspecific competition

An unusual predation form involves intraspecific competition between prey and predator belonging to the same species, known as cannibalism. It’s an important form of population control associated with stressed population, resulting into lowered reproduction and other demographic effects

Intraguild Predation (IGP) is very much different from traditional predation attributing to reduction in competition. It includes predators killing and eating of prey with similar resource utilization and gain energy and nutrients thereby differentiating it from classical competition. IGP is common in nature and have considerable effects on the ecological structure of communities. Most often mammal groups like felines and canines, and larger species like lions, wolves are involved in IGP. Among terrestrials arthropods IGP is well documented in insects and arachnids as by Harmonia spp. (figure. 16).

Figure.16: (IGP); (A) Harmonia sp eggs eaten by 3rd instar Harmonia axyridis larva, (B) Harmonia spprepupa eaten by 4rth instar Harmonia axyridis larvae and (C) Harmoniasp eggs eaten by adult Harmonia axyridis

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5. Host – Parasite Interaction

Among the most fascinating phrases of biology is parasitism dealing with the study of parasites and their relationship to their host species. It’s a branch of medical sciences where parasitologists observe parasites and their pathogenic effects on the host at all trophic levels. A parasite is a living organism which receives shelter and nourishment from another organism called as host, where it lives. Parasitism is a negative non-mutual symbiotic relationship where parasite obtains benefits at the cost of host fitness. Total dependency on host could be seen in parasitism. The association can be temporary or permanent. Nearly 300 species are parasitic to humans out of which 17 species belongs to protozoans. Four phyla of invertebrates are parasitic to animal kingdom including protozoans, platehelminthes, nematodes and arthropods. Parasite and its host association is a complex interaction

Parasitism is defined as a close and obligatory relationship between two heterospecific organisms during which usually the smaller of the two partners known as parasite is metabolically dependent on the host.

Parasitism have great influence on mate choice and may alter the sex ratios of hosts or its behaviour and can induce sterility, can enhance the death rates and decrease the birth rate, can affect the nutritional status and energy demands thereby influencing the interspecific or intraspecific competitions by increasing the vulnerability of host to predation.

5.1 Parasitic characteristics

Parasites include an array of taxonomic groups varying from invertebrates like arthropods to viruses, bacteria and fungi. A deviation from the normal body homeostasis leads to a condition known as disease, which can be an outcome of an infection due to the presence of a heavy load of parasites. However, not all parasites lead to diseased condition of host. Parasites can exploit their host showing diversity in ways and host may vary from plant to animal kingdom. Parasites superficially embedded in host body or attached to the outer surface of host are called ectoparasite for example mites, fleas and lice (figure. 17A). Those that live inside the host body in organs like liver, lungs, alimentary tract such as protozoa, bacteria and virus are known as endoparasite. An example is Schistosoma mansoni parasitizing in the blood vessels of human (figure. 17B). Those parasites which are both ectoparasite and endoparasites, living in an intermediate position are termed as mesoparasites. An example of mesoparasites is copepods mesoparasitizing on polychaetes (figure. 17C).

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Figure.17: (A) Ectoparasite: Head lice, (B) Endoparasite: Schistosoma mansoni, (C) Mesoparasites: Copepods.

Parasite have evolved diversity of means and degree of mobility ranging from totally dependent for locomotion on host to free-swimming types and hence, developed various ways to enter the host body and secure themselves from the hazards of living inside the host body. Many parasites require only one host for their entire life cycles while others exploit several hosts, without any specificity of order or genera.

5.2 Types of parasites

On the basis of size, parasites can be microparasite or macroparasite.

Table 1: Difference between microparasite and macroparasite.

S.No. Microparasite Macroparasite 1 Small size Relative larger size 2 Short generation time Longer generation time 3 Rapid multiplication Rarely direct multiplication 4 Induce immunity Short duration of immune response 5 Short duration of infection Persistence reinfection in host Direct/indirect transmission via intermediate 6 Direct transmission, via vector host/vector Eg. Helminths, parasitic worms (nematodes), 7 Eg. Viruses, bacteria, protozoan etc lice, mites, fungi, smuts, cuscuta, dooder plant etc

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Figure.18: (A) Microparasites: Ebola virus (B) Macroparasites: lice and (C) tongue eating louse attached to Lithonathus fish tongue.

Some plants also are parasitic in nature by themselves. For example, some plant macroparasites include a number of flowering plants. Plants that obtain nutrients, water and minerals from the host plant roots and are non-photosynthetic (lack chlorophyll) are grouped as “holoparasites”. Examples include Beechdrops (Eifagus virginiana) parasitizing on beech trees and squantroots on the roots of aoks, Dodder (Cuscutaspp) is a stem holoparasite (figure. 19A). Those photosynthetic plants that withdraw the nutrients and water from the host, for instance Mistletoes is an obligate stem parasite, are called “hemiparasites” (figure. 19B).

Figure.19: (A) Holoparasites: Cuscuta spp. (B) Hemiparasites: Mistletoes in north central texas

Depending upon the parasitic dependency on host, parasites can be categorized into two types; (a) “Facultative parasites” are those parasites which are not absolutely dependent on host for its life 20

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cycle also known as part-time parasite or temporary parasites. A fungus belonging to Russulaceae is parasitized by Monotropauniflora which is a myco- (figure.20A)(b) “Obligatory parasites” or full-time parasite or permanent parasites, are that organism that completely relies on the host for its entire life cycle or part of it. Most often facultative parasitism is among many species of fungi like genus Armillaria. Even if the tree dies, Armillaria without parasitic activity continues to digest the trees wood. (figure.20B)

Figure.20: (A) Facultative parasites: Monotropa and (B) Obligatory parasites: Armilliaria

Accidently acquiring and adapting for survival in an unnatural host is a characteristic of “incidental parasite”. Parasites are called “erratic parasites” based on the duration of host-parasite association, if it wanders into an organ in which it is not usually found. Few parasites obtain metabolic requirements by visiting their hosts after certain intervals are called “periodic parasites”. “Pathogenic parasites” are causative agents of acute or chronic disease in host.

Hyperparasitism

Traditionally hyperparasitism have been used as candidate agents for the substitution of chemical agents to control vectors of pathogenic parasites. A hyerparasitism is a condition of parasitisation on another parasite and the parasite is termed as “hyarparasite” or “epiparasite”. Cicinno boluscesatii is a pycnidial fungus growing parasitically on powdery mildew fungi.

5.3 Host as habitat

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The larger of the two associated organisms in the symbiotic interaction are host. Parasites are specialized for the extreme resource utilization and exploitation of every possible habitat within the host or on them. Hosts are home to parasites. Host is a source of nutrition and habitat for parasite. While moving from host to host several types of problems have to be encountered by the parasites. For animal parasites, the host are movable and therefore, they have evolved complex life cycle to relocate their host after escaping from one host during the transmission stage. Among many sites, some parasites live beneath the skin, some in bloodstream, and others in every possible organ of the body varying from gills of fish to lungs, and from mouthparts to the gonads, brain, stomach, eyes etc.

For most parasites, the major problem is (i) gaining access to the host body which produces many defence response from which they must escape and (ii) survive in the external environment while moving to the next host body. Parasites can move from one host to another only during a transmission stage via direct or indirect mode of transmission.

On the basis of life cycle the hosts can be classified as (a) the “Definitive or final or usually termed as obligatory hosts, one in which parasites become adult and attains sexual maturity. (b) Another classified form of hosts is Intermediate hosts which provide temporary and essential environment to harbour some developmental phases of life cycle. For example, trematodes harbour some part of their development in molluscs and arthropods thus acting as first and second intermediate hosts. (c) Other types are “Paratenic hosts” or “transfer hosts” which mainly serve as temporary carriers for obtaining access to definite hosts. Some arthropods are temporary refuge and vehicle for protozoans and other small parasites and referred to as “Vectors”. For example, Plasmodium spp., the protozoan malaria parasite, utilized various species of mosquitoes as vectors. (d) “Reservoir hosts” are those infected hosts that serve as a source of infection to other hosts. For example, in Malaysia a type of filariasis is transmitted from human to human through mosquitoes as vector, also infecting cats and monkeys. These infected cats and monkeys are reservoir hosts for the establishment of human infection.

5.4 Disease and parasitism:

Parasites are enemies that cause disease in animals or plants etc. They may eliminate species from areas and thereby restrict geographical distributions. Disease and parasites have always been a major factor in the ecology of humans. Their role in geographical ecology of plants and animals has been studied much lesser than their potential importance would warrant. An example involves the native bird fauna of Hawaii. A large fraction of the endemic bird species of the Hawaiian Island has become extinct in recent times; one possible reason for these losses is introduced disease. Avian malaria and 22

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avian pox are the main cause of these losses cited by Warner in 1968. The mosquito Culex quinquefasciatus, is the main malaria vector. The transmission of disease from invertebrates to humans is termed as “Zoonosis”. Recently WHO proclaimed six major human diseases in the world and Leprosy caused by bacterium, others are Schistosomiasis, malaria, filariasis, Leishmaniais and African trypanosomiasis are the parasites in the traditional sense.

Effect of parasites on hosts

In parasitism, one partner (parasite) among the two-interacting species can cause injury to the other partner (host). The injuries vary in their degrees of alternation within host and some may leads to diseases, although disease is mainly attributed to high density of parasites. When the parasite is present in low density within host, it depicts asymptomatic disease stage but based on the host physiological condition and high density of parasites the onset of symptoms appears for the recognisable diseases. Herein, in Table 2, the effects of parasites on host tissue with their proper explanations are suggested.

Table 2: Examples and explanations of effects of host-parasite interactions on host. Effects of host- S.N Eg. parasite Explanation Eg. Parasite Group o Hosts/sites association a.Inflammation,damage Connective Hookworm Nematodes to tissues, dermatitis tissue Destruction of 1. b. minute to appreciable Hosts Tissues damage to intestinal Host intestine Flukes and tapeworm Helminthes lumen a.Hyperplasia Bile ducts Liver fluke fasciolaspp Helminthes Enlarged b.Hypertrophy Plasmodium vivax Invertebrates RBC’s Fluke 2. Tissue changes c.Metaplasia Human lungs Paragonimuswesterma Helminthes ni Several species of d.Neoplasia mammals Helminthes parasite Broad fish tapeworms, Competition for 3. Pernicious anaemia Human blood Diphyllobothriumlatu Helminthes host nutrition m Utilization of non Ticks, leeches: Humans and 4. nutritional Anaemia Harmadipsa, Nematodes animals materials Necatoramericanus Humans Mechanical Filarial 5. Elephantiasis (lymphatic Wuchereriabancrofti Interference Nematodes ducts) 23

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5.5 Social parasitism

Social parasitism is a form of parasitic relationship in which one organism is parasitically dependent on other members of the society of social organisms. Examples of social parasitism are ants, termites, bumblebees etc. Social parasitism has two forms brood parasitism and kleptoparasitism.

a. Brood parasitism

Some organisms are in practice of laying eggs in the nest of surrogate parents that take care of their young ones. This type of parasitism is practiced by cowbirds, cuckoos, wydahs and black- headed ducks. These organisms do not build their own nests, thereby parasitizing on the nest of other species, for exampleReed warbler cuckoo, Eastern Phoebe nest,egg of Brown-headed- Cowbird in other species nestetc (figure.21A, B). This type of parasitism can be facultative or obligatory, permanent or temporary. Permanent facultative brood parasitism may occur among or within species. Permanent obligatory is a type of brood parasitism where organism parasitized on the nest of host for its entire life cycle. Among animals one species of ants exploit another species in respect of shelter and slave labor. Formica nests are raided by the workers of another ant species, Polyergus. Formica workers then feed and build nests for Polyergus.

Figure.21: (A) Brood parasitism in Reed warbler cuckoo and (B) Eastern Phoebe nest Brown-headed- Cowbird-egg

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b. Kleptoparasitism

Parasites steal a substantial portion of food from the host, an association known as kleptoparasitism. It is mostly prevalent among two groups of birds, the Falciformes (eagle, hawks etc) and Charadriiformes (gulls, waders etc). For example, an eagle retrieves and eats fishes caught by an osprey which is dropped forcibly by the eagle.

6. Summary

Indeed negative interactions have a peculiar role in shaping the community structure and stability. A negative interaction involves antibiosis where growth of one species is inhibited by another through chemical aggregation. It also includes synnecrosis which is a rare detrimental association ultimately leading to death of one of the interacting species. Ammensalism is another negative interaction to only one interacting species with no harm to other. Allelopathy is a form of intraspecific competition occurring between plants by secreting chemical substances and inhibiting the growth of others. Competition is grouped into intraspecific competition also known as scramble competition, occurring between individuals of same species and interspecific competition or interference or consent competition, an interaction between different populations. Interspecific competition may be of two type’s interference and exploitative. Exploitative competition exists where resources are in short supply, thereby reducing the fitness of interacting individuals of two or more species. Exploitative competition limits resources to either population while interference is because of aggressive interaction. Lotka-Voltera is the classical mathematical logistic model of competition predicting four types of outcomes of the relationship between two interacting species sharing same resources. This model led to Gause’s principle or competition exclusion principle which explains that no two species can coexist with same ecological requirements, which later on stimulated other competitive associations like coexistence of species and resource partitioning. Coexistence is possible when resource supply is in equilibrium with resource consumption. Resource partitioning occurs where interacting species which differ in their requirements of limiting raw materials like light, nutrients etc competes simultaneously. Interspecific competition is closely associated with the concept of “niche”, playing functional role in the community. Fundamental niche is which an organism occupies in the absence of competition. Under the influence of interspecific competition, organism exists in more reduced form of fundamental niche called “realized niche”. Predator- prey system is a type of association in which predators interacts with their prey. Under plant predation comes herbivory that affects plant fitness. Host and parasites live together in which parasites gain its nourishment at the expense of its host, a condition called as parasitism. Parasites can be microparasite or macroparasite 25

Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2

that differ in size, generation period, multiplicity and mode of transmission. Parasites living outside the host body are ectoparasites and those present inside the host body are called endoparasites. Entrance and escaping from the host body is the main problem faced by the parasites for their transmission. Other type of parasitism is social parasitism which involves brood parasitism and kleptoparasitism. Brood parasitism may be permanent or temporary, obligatory or facultative and mainly common among wasps, ants and birds. Kleptoparasitism is more prevalent among hawks, eagles and gulls. A parasite infection can lead to a state that deviates from normal well being called disease.

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Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2