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Host and parasite interaction
- 1. HOST AND PARASITE INTERACTIONS Devina Seram Ph. D. (Agricultural Entomology)
- 2. Parasite and parasitism Kinds of Parasite & Number of Parasitic insect species Adaptive Radiation of Parasites Life History Convergence Phylogenetic Relationships Host Defenses against Parasites (Response) Host Behavioural Modification by Parasites Applications
- 3. Organism living in or on another living organism, obtaining its nutrition from that host organism and causing some degree of measurable damage to the host (play role in ecology and evolution) Parasitoid – Organisms having parasitic immatures, free-living adults that find host where they deposit eggs or living larvae, kill the host Reuter (1913) – “Parasite-like-predator” – impact on insect populations equivalent to predators – mostly impact on host survival, distribution, abundance & popu. dynamics of many species
- 4. Kinds of Parasitic Insect & others with parasitic life cycles
- 5. Kinds of Parasitic Insect & others with parasitic life cycles
- 6. • 13,20,000 (and growing) estimated described animal species in world (Hawksworth & Kalin-Arroyo, 1995) 1,05,170 metazoan parasites on animals (Poulin,2007) – 82,131 parasitoid species (Godfray,1994) – total of 1,87,301 parasite species on animals Large proportion of fauna – insects with parasitic life – total of 70.7% Species richness – parasitic Hymenoptera with 5342 species – 89% of parasites on animals “ the total will be considerably increased when the Parasitica are better known”
- 8. 10 largest insect families in categories of Predators, Herbivoros parasites & Carnivoros parasites (Kloet & Hincks, 1945)
- 9. • Host not only provides food but also habitat to live • Mammalian integument for parasites to live • Letters indicate distinct niches colonized by certain kinds of mite (Nutting, 1985)
- 10. The diversification of a group of organisms into forms filling different ecological niches Reasons : • High specificity to host species – most salient • No. of hosts available in the lineage of hosts Eichler’s Rule (Eichler, 1948) states that the diversity of parasitic fauna will as the host taxon s Adaptive Radiation of Parasites Short generation time Discrete microhabitat by host High populations
- 12. - Tendency to evolve similar characters under same envtl. conditions • Common problem to parasites (with their small size & wide hosts) is the transmission from one host to another or infection/colonization of new hosts • To overcome – complex life cycles evolved with several distinct stages (asexual & sexual reprodn.) • Convergence in reproductive strategy : Convergence of Life Cycles Parasitoid oviposit on foliage – infection of host when egg is eaten or hatched larva attaches to passing host Parasitoid oviposit directly into host stage – life cycle completed
- 13. Converge nce of life cycles among 4 types of Parasite
- 14. Polyembryony : Encyrtidae, Platygasteridae, Dryinidae, Braconidae Precocious larvae & caste formation Haplodiploidy & Sex Ratio Parthenogenesis : Thelytokous in parasitoid wasps 20 families & 205 species Heteronomy : Aphelinid - ♀ as endoparasitoid, ♂ as hyperparasitoid Inbreeding / Sib mating Hypermetamorphosis : Meloidae – triungulin planidium Extended Phenotypes : Gall inducing insects Adaptive Traits in Parasites
- 15. Life cycle of Swaine jack pine sawfly & parasitoids attacking each stage Extended Phenotype (Neodiprion swainei)
- 16. • Phylogenetic tracking of host lineages • Evolutionary development and diversification of parasitic species or groups of parasite • When parasites live closely associated with hosts, parallel evolution takes place such that when host speciates, parasite will also speciate (Co-speciation) Mostly parasites on plants (herbivorous insects) Phylogenetic Relationships
- 19. Gross (1993) – 3 main categories: 1. Properties of host that minimize chance of being found 2. Behavioural & morphological defenses that reduce parasitoid ability to attack 3. Internal physiological mechanisms that kill parasitoid eggs or larvae 5 categories of defenses: 1. Morphological - toughened egg chorion, tough integument in larvae, puparium in pupa 2. Evasive – wriggling, dropping on thread 3. Aggressive – biting, secretion/ejection of chemicals 4. Protection by attending ants 5. Parental care of eggs/immatures Host Defenses against Parasites
- 20. All forms of defense by insects against parasitoids affect both the number of parasitoids adapted to any host species and the level of mortality inflicted
- 21. Relationship b/w host feeding niche & % parasitism per host Hawkins (1994) categorized host feeding niche
- 22. While host evolve with behaviours that reduce infection & transmission of parasites, parasites have also evolved to increase the probability of infection (Moore, 2001) Many parasitoids known to alter host behaviour : Caterpillars adopting more conspicuous feeding sites Moving higher on foliage Shifting from nocturnal to diurnal feeding Negative phototaxis Concealment of aphids from possible predators & hyperparasitoids Host Behavioural Modification by Parasites
- 23. • Interaction of acanthocephalan (Plagiorhynchus cylindracus) when it infects pillbugs (secretive in litter),which then move into exposed sites where they are easily spotted & eaten by starling (definitive host) 1. In starling, a mature ♀ parasite lay eggs – released in faeces 2. Pillbug consumes faeces & get infected 3. Pillbug eaten by starling Starling Pillbug
- 24. Summary & Conclusion • One most imp. consideration - evolutionary potential – the numbers of parasitic species are vast since they evolve rapidly, ecological niches are highly specialized and thus high adaptive radiation • Challenges to applying knowledge to solve parasite- related issues : 1. to develop sophisticated understanding of the epidemiology of each parasite species 2. to find effective methods of regulating pests – IPM, BC 3. to prevent the evolution of resistance to whatever mechanism is used Parasite – harmful or beneficial – depending upon the trophic level at which they work
Editor's Notes
- Convergenge of many groups toward similar life cycles / All these contribute to the parasite’s ecological and evolutionary roles
- Main recognition of herbivorous insects as parasites is provided in the definition of gall (abnormal growth formed from tissues of a plant or other host due to the parasitic activity of another organism)/ Most caterpillars (but not all) spend their lives on a single host plant, eating plant tissues and causing real damage: they qualify as parasites / Parasitism applies to majority of the insect herbivores
- Various estimates made on no. of parasitic species in any fauna / If we add parasites on plants plus bacterial, protozoan and fungal parasites would increase the % (not to mention the undescribed species / Also parasites have become much richer in species than predators / It was stated in British Hymenoptera that “ the total will be considerably increased when the Parasitica are better known”
- Insect orders and the number of insect species parasitic on different hosts
- Among carnivorous parasites, most parasitoid families are from Hymenoptera / Tachinidae with 228 species is a large family of dipteran parasitoids / Philopteridae (Pthiraptera) bird lice is the only non-parasitoid family listed / 8 of the 10 largest families of carnivorous parasites are Hy para / Cecidomyiidae among herbivorous parasites tops the chart with 629 species having intimate host-plant and parasitic interaction
- A – occular or oral cavity, B – blood vessels, D – dermis, E – epidermis, F – hair in follicle, L – eye lid, M – mixed apocrine & eccrine glands, N – lymph node, O – oral cavity, P – epidermal pits, S – sebaceous holocrine gland, T – tarsal gland, etc.
- Many reasons exists for the extensive adaptive radiation of parasitic groups - These three factors provide the ingredients for rapid speciation and adaptive radiation of parasites (Distinct) Microhabitat – a habitat of limited extent which differs in character from the surrounding habitat Body design, physiology, life cycle, popu. size & dynamics, community structure, evolutionary potential & adaptive radiation – involved with size of parasite (small sized)
- No. of host species recorded for parasitic insects on plants, insects, mammals and birds / High specificity is recorded in ichneumonids & braconids with 53% & 60 % of parasites attacking a single host / Bird lice are also highly specific with 87% of species recorded as specific to a single host / those families with > 50% of species with only one host have a very intimate relationship with that host
- Convergence (of unrelated animals and plants) – tendency to evolve superficially similar characteristics under similar environmental conditions here, parasitoid fecundity is very high thus compensating for the low chances of host infection Parasitoid fecundity low because the probability of survival is high
- The convergence of life cycles among 4 types of parasite: liver fluke/gall aphid/gall adelgid and rust fungus Similarity of multiple stages of asexual reproduction & single sexual reprdn. Resulting in a egg or basidiophore
- Evolutionary Convergence into the parasitoid way of life provides one of the best & most diverse egs. – convergence being the path of disparate (essentially diff.) taxa evolving towards a common body plan or life-history type
- Neodiprion swainei (host) offers a series of diff. resources which can be attacked by parasitoids : 2 primary egg parasitoids – 4 primary larval parasitoid (Perilampus oviposit on foliage, active 1st instar larva planidium hatch & wait for passing sawfly larva,climb,bore into host & become endoparasitoid / Spathimeigenia, larviparous, injects 1st instar maggots into host & become endoparasitoid /Olesicampe & Lamachus attacks early & later instar larva
- Phylogenetic – evolutionary development and diversification of a species or group of organisms
- Phylogenetic relationships of host and parasite species through time, with time passing from bottom to top in each example: (a) host and parasite species diverge and speciate in synchrony; (b) a parasite species shifts from one host to another, expanding its range of hosts; (c)speciation in the parasite lineage occurs on a single host lineage; (d) the parasite species goes extinct; (e) the host speciates without the parasite colonizing the new species; (f) the host speciates, but the parasite does not, although it remains on both hosts
- Comparison of phylogenetic hypotheses for the beetle genus Phyllobrotica and its sister genus Haplasoma and the host plants in Scutellaria and related genera – Phylogenetic tracking of host plants by insect herbivores involves Phyllobrotica beetle utilizing members of lamiaceae plant family
- When parasites attack hosts, host also evolve some countermeasures in the form of immune response, physiological mechanisms, association with protective mutualists, morphological & behavioral modifications, secretive function – all these traits are observed in insects in response to parasitoids Use of refugia from attack, leaving food plants or feeding damage or moving away from frass use of armor, evasion. Defensive secretions and aggressive movements Encapsulation, sequestration of plant allelochemicals or synthesis of toxins by insects themselves (in plants, defense against parasites by producing hypersensitive response)
- Relationship b/w host-insect feeding niche and mean of the highest parasitism rate recorded per host species
- Interaction of starling (bird) with pillbug (Armadillium vulgare – acting as intermediate host) as prey and acanthocephalan (parasitic worm) parasite (Plagiorhynchus cylindracus) that lives in bird’s intestine. Infected pillbug has altered behaviour i.e. it moves from shady & moist litter into open spaces where it is more likely to be spotted & devoured by a starling – thus enabling parasite transmission from one bird host to another