Parasitology notes PDF

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Parasitology: study of the most common mode of life on earth. o Centered on animal parasites of humans, domestic animals and wildlife.  Parasite: an organism that lives in or on another organism (host) and either harms the host or lives at the expense of the host.  Why is parasitology important? o Parasite resistance o Insecticide resistance o  Table 1.1 some human infections with parasites  Humans have acquired about 300 species of helminth worms and over 70 species of protozoa  Trichuris trichiura  Whipworm  Rectal prolapse is the main symptom  Hookworms  Bore into your skin  Clicker 1: how many hours of studying per week should be dedicated to parasitology lecture to be successful in this course? C. 3x3=9 hrs per week o Parasitic fungus Ophiocorduceps unilateralis  Fungal parasite  Has a convulsive episode which throws them off the branch and allows parasite to take over the body which turns them basically into a zombie o Pocketbook mussel (Lampsilis ovata)  Parasitic freshwater fish  Acts like a lure to attract bigger fish where the clam will spit out in the face of the fish and the fish clamp on to the gill arches and receive nutrients for about 3 or so weeks o Tongue eating isopod (Cymothoa exigua)  Crustacean parasite  Female clamps on to the base of the tongue and feed off the mucus and blood of the fish while male clamps on to the gill arches o Common vampire bat (Desmodus rotundus)  Remote parasite?  Land near the host and crawl towards host and thermal reception figures out where the veins and release an anti-coagulant and anesthetic and feed off your blood o Cuscuta sp. (dodder vine)  Parasitic plant  Seeds will germinate which have 5-7 days to find a host  Use haustoria to obtain host’s nutrients o Common cuckoo (Cuculus canorus) raised by Reed Warbler (Acrocephalus sp.)  Parasitic bird  1% of bird species brew parasitism

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Parasitism – think of the nest as the birds external uterus, part of body  Spies on nests and when female goes away the cuckoo bird will swallow one of the eggs and dispel an egg. Egg will hatch 48 hrs before hosts egg and pushes out the other eggs from nest.  Can have up to 20 eggs and hit up 20 different nests o Candiru or toothpick fish (Vindellia cirrhosa)  Fish parasite  Goes after host fish, clamps onto gills arches, sucks blood from arches. Finds host by the release of urea  Some cases where someone urinated in river and fish went up the urethra of that person o Pelophylax lessonae (small (chihuahua))  Fertilizes the egg  Does good in free flowing waters o Pelophylax ridibunda (large (great dane))  Hybridogenesis: the gametes that it has to offer to the next generation, no genetic material from the lessonae is present. The gametes only show representation of ridibunda  Amphibian parasite, genome parasites  Hybridize Parasitologist: quant person who seeks truth in strange places; a person who sits on one stool, staring at another. Basic Organismal interactions o Symbiosis: interaction among organisms in which one organism lives with, in, or on the body of another. o Symbionts: organisms involved in symbiotic relationship with other organisms, the hosts. o Neutralism: is a lack of benefit or detriment experienced by either members of the pair of interaction organisms.  It describes interactions where the fitness of one species has absolutely no effect whatsoever on that of the other.  Ex: remove all the beetles of the preserve and see how that affects the grass, etc.  Falls under symbiosis  + helping – harming 0 neither, this interaction would receive 0. o Competition: some degree of overlap in ecological niches of two populations in the same community, such that both depend on the same food source, shelter, or other resources, and negatively affect each other’s survival.  Whenever there’s competition, both competing are negatively affected  Ex: Carnivorous animals compete for prey o Cape Buffalo (Battle at Kruger)  Ex: Plants compete for sunlight, water, nutrients, pollinators, and dispersers of fruits and seeds. 

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o Growing out secondary compounds on each other Ex: The bladderwort plant (Utricularia) compete with tiny fishes for small crustaceans and insects. o Phoresis: form of symbiosis when the symbiont (phoront) is mechanically carried about by its host: neither is physiologically dependent on the other.  Means “to carry”  Ex: bacteria on legs of a fly  Ex: fungal spores on feet of a beetle  Ex: aquatic snail eggs laid on birds feet  Ex: Dermatobia hominis (human botfly) o Female botfly deposits egg on surface of mosquito o Protocooperation: a mutually beneficial symbiosis between organisms in which the interaction is not physiologically necessary to the survival of either  Ex: Egyptian plover eats residuals from crocodile teeth  Ex: cattle egret removes ectoparasites from the back of bovines  Ex: hermit crab inside shell over which sea anemones live  Protect from fish  Anemones get a free ride  Ex: ants and aphids  Dew comes out of anus of ant which is a rich watery solution  Clicker 2: which set of symbols below would best represent the organismal interaction between a lioness and crocodile preying upon the same water buffalo? B. (-,-) o Mutualism: type of symbiosis in which both host and symbiont benefit from association  Usually obligatory  In most cases there is physiological dependence  Termites and intestinal protozoan fauna  Blood-sucking leaches and intestinal bacteria  Cleaning symbiosis: cleaner wrasse (Labroides dimidiatus)  Lichen: microscopic green algae or cyanobacteria and filamentous fungi o Good biological indicator o If you eliminate the cyanobactera, the fungi will die = mutualism o (+,+)  Wuchereria bancrofti and Onchocerca volvulus infected with Wolbachia  Mycorrhizae (fungus-root)  Nitrogen fixation, the bacteria Rhizobium spp. o Commensalism: a kind of symbiosis in which the symbiont (a commensal) benefits, and the host is neither harmed nor helped by the association  Means “eating at the same table”  Pilot fish and remoras  Entamoeba gingivalis 

 Barnacle on a whale  Epiphytes on a tree  Clicker 3: which set of symbols below would best represent the organismal interaction between an elephant and organisms beneath its feet? B. (0,-) 

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Ways to describe parasites: o Permanent parasite: living in the host the whole entire time as an adult o Endo parasites: inside o Ecto parasites: outside o Accidental parasites:  Usually in dogs and winds up in humans o Parasitoids: o Organism that needs a host but stays on host for short period of time  Ex: fleas o Obligate: have to have their host or they won’t survive or be able to produce next generation o Hyper parasitism: o Predation vs Parasitism o Both the parasite and the predator live at the expense of the host of prey; interaction occurs only if there is an encounter Basic organismal interactions cont. o Amensalism: asymmetrical interaction in which one organism causes a negative effect on another without being positively or negatively affected in return.  Ex: bread mold Penicillium that produces penicillin, an antibiotic that kills bacteria  Ex: Black walnut tree (juglans nigra) produces juglone, an organic compound that is toxic or growth-stunting to many types of plants How to describe parasites o Coelozoic: a parasite living in the lumen of a hollow organ  Ex: intestine o Histozoic: a parasite living within the tissues of the a host  Ex: liver  As an adult its target organ is going to be a solid body organ like deep within the liver or tissue How parasites are transferred to host o Vector: any agent such as water, wind, or insect (host), that transmits a disease organism o A beautiful stream and parasite going from point A to point B How to describe hosts o Definitive host: host in which a parasite achieves sexual maturity; if there is no sexual production in the life of the parasite, the host most important to humans is the definitive host

o Intermediate host: host in which a parasite develops to some extent but not to sexual maturity  you can have multiple of these o Paratenic (transport) host: host in which a parasites survives without undergoing further development  Host that is utilized to get from point A to point B  Belongs in the food chain that will lead to the definitive host o Reservoir host: serves as a means of sustaining a parasite when it is not infecting humans, which is typically another suitable definitive host  if we’re not around and there’s another host that the parasite can complete its cycle, it will go to that host

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life cycle of Giant kidney worm (Dioctophyme renale) Dog is definitive host The nematode has male and female who reproduce in the kidney of the dog; usually the right kidney The eggs come out in the dogs urine then the earth worm eats the egg 3rd stage is the infection stage

How to describe life cycles o Urban (domestic) cycle - Normal to the human environment - Involves domesticated animals o Sylvatic cycle - Existing normally in the wild - Involves wildlife

 Clicker 4: Which of the following parasitological terms would not accurately represent this picture? C. Histozoic

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Host-parasite coevolution o Population: any group of individuals, usually of a single species, occupying a given area at the same time. o Mutation: a permanent change in a cell’s DNA and includes: changes in nucleotide sequence, alteration of gene position, gene loss or duplication, and insertion of foreign sequences  A mutation is NOT a key mechanism of evolution o Selective valve (adaptive value): the relative reproductive success (relative fitness) of an allele or genotype as compared to other alleles or genotypes. o Preadaptation: the possession of a trait that coincidentally predisposes an organism for survival in an environment different from those encountered in its evolutionary history; may occur because a natural population carries a huge quantity of genetic variability.  Ex: dinosaurs feathers initially used for insulation and display  Ex: origin of larynx initially helped air-breathing fish gulp air o Adaptation: an evolutionary process whereby a population becomes better suited to its habitat over many generations - An anatomical structure, a physiological process, or behavioral trait that promotes the likelihood of an organism’s survival and reproduction in a particular environment  Ex: adaptation of parasite to host internal environment  o Selection: a composite of all the forces that cause differential survival and differential reproduction among genetic variants (artificial selection vs. natural selection); a key mechanism of evolution  Ex: reciprocal selection pressures exists between parasites and their hosts (hosts select for the best parasites and parasites select for their best hosts)  MEANING: the hosts that parasites can get into easily are being robbed of nutrients so overtime parasites are selective for the best hosts because those hosts are avoiding contact  The ones who have a higher fitness will be able to pass on more of their genetic material  Selective for THIS because everything else is being whipped out

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the prey selects for the best predator because within the arctic fox population you share the same meal Some are more agile than others, some know where you can most likely find the prey, some can blend better

Sirciria have a genetically inheritable trait that are negatively photopathic The parasites that are able to make contact with the fish are going to be selective for The ones to the right will be eliminated and will not be able to pass down genetic material Have a population of the same fish but a few that have a genetically inheritable trait that makes them want to stay at the bottom whereas the others want to stay at the top so over time the fish at the bottom will increase and the ones at the top will decrease Host-parasite evolution o Evolution: genetic changes in populations of organisms through time that lead to differences among them - Evolution only occurs when there is a change in gene frequency within a population over time

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These genetic differences are heritable and can be passed on to the next generation

Host-parasite coevolution cont. o It is in the best interest of the parasite to possess adaptions that allow it: 1. To encounter the host - Parasites that posses a genetically determined behavioral trait that increases the probability of encountering the host will be positively selected for 2. To survive in the host If the encounter has occurred - Parasites whose genetically determined traits allow them to survive the host’s immune system will be positively selected for o It is in the best interest of the host to possess adaptions that allow it: 1. Avoid encountering the parasite - Hosts that behave in a genetically determined way that reduces its probability of encountering a parasite will be positively selected for 2. To get rid of the parasite if an encounter has taken place - Hosts whose genetically determined traits allow them to eliminated the parasite will be positively selected for

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o Red Queen Hypothesis: originally proposed by Leigh Van Valen (1973) - Metaphor of Alice and the Red Queen from “Through the Looking Glass” - Species have to “run” (evolve) in order to stay in the same place (extant) - Cessation of change may result in extinction  Ex. Parasite-Host Coevolution  Each time the parasite population acquires a new “weapon” (ex. New antigen”, the host population is led to produce a new defense (new antibody, directed at this antigen) o Parasite and host population are engaged in an “endless” arms race/war Adaptations for Parasite Transmission A. Reproductive: produce more eggs and sperm than their free-living relatives do 1. High reproductive potential 2. Asexual reproduction 3. Hermaphroditism 4. Self-fertilization

B. Behavioral 1. Adaptive advantage of parasite behavior a. Ex: Schistosoma mansoni cercariae

2. Parasite may alter host behavior a. Ex: Dicrocoelium species Cow -> Snail -> Ant -> Cow C. Morphological adaptations 1. Size – many parasites are larger than their free living relatives 2. Attachment organs – suckers, hooks & spines, penetration organs, and cysts, etc. 3. Loss (regression) of anatomical structure – organs of sense, locomotion, digestion, etc. D. Biochemical adaptions 1. Energy metabolism – catabolic pathways are usually reduced or modified in many parasites 2. Nutrient uptake – there is an elaboration of transport mechanisms 3. Synthetic reactions – synthetic capacities of parasites are reduced when compared with their free-living relatives E. Immunological adaptions 1. Absorption of host antigen Ex: Schistosoma spp. 2. Antigenetic variation Ex: Trypanosoma brucei (VATs), Giardia *** missing notes from Friday 9/13*** 

How to identify a species? o Taxonomy: Study of scientific classification; ordering & naming organisms - Basic subdiscipline of biology - Scientific name carries with it massive amounts of information - Includes (a) through (d) (a) Describe organism in detail (utilize morphological and molecular characters) (b) Provide scientific names for new species (c) Preserve collections (permanent slides and voucher specimens) (d) Classification of the organisms, keys for their identification, and data on their distributions (e) Investigates their evolutionary histories

(f) Considers their environmental adaptations o Systematics: study of classification & biological diversity within an evolutionary context - Seek to understand the origin of diversity at all levels of classification - Includes (a) through (f) (a) Describe organism in detail (utilize morphological and molecular characters) (b) Provide scientific names for new species (c) Preserve collections (permanent slides and voucher specimens) (d) Classification of the organisms, keys for their identification, and data on their distributions (e) Investigates their evolutionary histories (f) Considers their environmental adaptations Investigating the evolutionary history of a taxon is not easy. Why? Unfortunately, history: - Is not something we can see o Only happened once o Only leaves behind clues  Systematics use clues to try to reconstruct evolutionary history. Why?  To research the pattern of events that have led to the distribution & diversity of life. o Phylogenetic systematics (cladistics): is a methodology used by systematists o infer (hypothesize) a species’ evolutionary history (phylogeny) - Pioneered by Willi Hennig ( o “father of systematics” - Used in the discovery of monophyletic groups (evolutionary real entities) - This method exclusively relies on shared derived character states (homology) o There are 3 basic assumptions in cladisitics: 1. Change in characteristics occurs in lineages or groups over time - only when characteristics change are we able to recognize different lineages 2. 3.  

o Phylogeny – evolutionary hypothesis of the origin and diversification of a taxon - Treelike diagram - Relationships between taxa are shown in the branching patterns - Characters among the taxa used to produce phylogenies include: (anatomical, behavioral, physiological, or molecular attributes)

o Clade: a group of organisms that includes an ancestor and all descendants of that ancestor 

How to describe a species? o Ingroup: a taxon of interest o Outgroup: a related taxon chosen for the purpose of comparison  Always more basic  Branched out before the ingroup  Ex: bony fish (ingroup) & sharks or rays (outgroup) o Node: internal branch point that represents the common ancestor of those descendants; a speciation event o Sistergroup: two descendants that split from the same node

Homologous character: a character is similar (or present) in two taxa because their common ancestor had that character.  Analogous character: a similar character that has the same function but different evolutionary origin  Homoplasy: is similarity NOT due to homology; resulting from convergence , parallelism or reversal  An erroneous outcome o Ex. of convergence: sharks and dolphins o Ex. of reversal: whales because they once were terrestrial and had legs and now they have stubs o Ex. of parallelism: batesian mimicry (coral snake and scarlet king snake) (the monarch butterfly & the copy butterfly: if bird eats monarch they remember the bad taste so when they see the copy they remember the taste and won’t eat the copy)  Plesiomorphic: ancestral characters; present in both the ingroup and outgroup - uninformative character o Autapomorphic: derived character; evolutionary novelty; present only in one taxon of the ingroup - uninformative character o Synapomorphies: shared derived characters that set a taxon apart from related taxa and their most recent common ancestor - informative character - new novel or derived - shared with more than one member 

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How to describe groups?  Monophyletic: a group of taxa that includes a hypothetical ancestral taxon and all its descendants - Defined by a suite of shared-derived characters (synapomorphies) Ex: mammals  Paraphyletic: a group of taxa that includes a hypothetical ancestor but does not include all of th ancestors descendants - Defined by a suite of ancestral traits (plesimorphies) which have been modified or lost in the excluded species. Ex: class Reptilia is paraphyletic by not including birds 

o Species A through J that group of scientists are trying to learn more about o Scientists hypothesize that species B, C, D and E, F, G and H, I, J are more closely related than anything else o H, I & J are monophyletic group because they share a common ancestor and all descendants of that ancestor o B, C & D are paraphyletic group because they include the common ancestor but not all of ancestor’s descendants o E, F & G are polyphyletic group because they do not include the common ancestor of the group

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