Paper : 08 Biology of Parasitism 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 1 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 competition, Exploitation competition, Competitive Exclusion Principle, Character Displacement, Predation 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. Resource Partitioning 2 Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2 4. Predation and Parasitism 5. Host -Parasite Interaction 5.1 Parasitic characteristics 5.2 Types of parasites 5.3 Host as habitat 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 community structure. Learn how negative interactions help in the process of colonization. Know different types of negative interactions in the ecosystem 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 plants. V.E. Shelford and F.E. Clements, 1939, tied plant and animal ecology 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, predations have enhanced influence on community by affecting one or more trophic levels. R. MacArthur (1955) stated that simple food web 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 organism 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 antibiotics 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 bacteria. 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 microorganisms harmful to one or both. 4 Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2 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 organisms of its own kind of species 6 Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2 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 heterotrophs and inorganic food, light and water in autotrophs, (b) habitat to grow hide, from predators etc. Competition is an area of population ecology 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 7 Biology of Parasitism ZOOLOGY Animal Association and Host- Parasite Interaction. Part 2 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