Download Symbioses and Parasitism - Powerpoint for Oct. 23.

Symbiosis
Symbiosis
• Symbioses - species living in close
association
• Parasitism +,- parasite benefits, host
harmed
• Commensalism +,0 or 0,0 can have
positive effect for one species or for
neither
• Mutualism +,+ both species benefit
Gopher Tortoise – Commensal Host
Gopher Tortoise Distribution
Epiphytes
Bird’s Nest
Fern
Nalini Nadkarni
studying
epiphytes
Epiphytes
Figure 1: Hypothetical tree illustrating how
vascular epiphytes in humid forests tend to
partition substrates illustrating sensitivity to
micro climate, particularly humidity, and
associated development of the organic rooting
media required by some populations.
Parasitism and Disease
Lyme Disease Cycle in the UK
Parasitism
• Parasitism - intimate association between two
species in which the parasite obtains its
nutrients from a host - parasite usually causes
some degree of harm to its host - either
reduced growth or reproduction
• Pathogen – disease causing agent
• Disease – abnormal condition of host due to
infection by a pathogen that impairs
physiological functioning
Parasites on
Plants
Arthropods are green,
Fungi are brown,
Worms are blue,
Protozoa are yellow
Parasitism occurs on a continuum from:
• ectoparasites - live outside hosts body and
experience same conditions as host - ticks,
mites, fleas, aphids
• endoparasites - live inside host's body cavity buffered from outside conditions - tapeworms,
flukes
• intracellular parasites - live inside individual
cells of the host - viruses, bacteria, protozoa often called microparasites
Or another way to divide parasites:
• microparasites - viruses, bacteria, protozoa - small,
often live intracellularly, main point is that they
reproduce in host and will have very large numbers in
host
• macroparasites - tiny to very large - nematodes,
tapeworms, flukes - larger individuals that grow in
host but multiply by producing infective stages that
are shed by host to environment where they infect
new hosts
Parasite Transmission
• Direct transmission – from one host to another
of the same species via air, water, coughing,
blood, feces, etc.
• Indirect transmission – from one host to
another of the same species via another species
called a vector
• Vector – species which transmits parasite or
pathogen from one host to another
Microparasites
Macroparasites
Direct
transmission
HIV virus,
Amoebic
dysentery,
Mildews on plants
Indirect
transmission
Plasmodium
(mosquito),
Plant viruses
(aphids),
Trypanosoma
(tsetse fly)
Lice, fleas, ticks,
aphids,
hookworm,
pinworm,
mistletoe
Tapeworms,
Schistosomes
(snails),
Rust fungi
Powdery Mildew on Grape Leaf
Powdery Mildew Life Cycle
Head Lice and Life Cycle
Mistletoe
Mistletoe Life Cycle
Malaria disease cycle
Past and Current Malaria Areas
Potential spread of malaria by 2050
Schistosomiasis - Life cycle of the
schistosome worm
Worldwide incidence of schistosomiasis
Worldwide incidence of schistosomiasis
Rust Fungus Canker
Rust Fungus Life Cycle
Two ways to study parasite numbers
• Prevalence – percent of host population
that is infected – best for microparasites
• Intensity – number of parasite individuals
per host – usually best for macroparasites
Parasite burden (intensity of infection)
Model data
Parasite burden in bluegills
Bluegill trematode parasites
Frequency of infection
Parasites usually occur in aggregated distributions – due
to 4 possible factors:
1) random colonization events followed by asexual
reproduction in hosts that do get parasitized
2) environmental "hot spots" where parasite eggs and
infective stages survive well
3) dispersal constraints - geographic or behavioral
barriers limit dispersal of parasites to just a few hosts
4) variation in susceptibility of individual hosts - due to
nutrition, genetics
European rabbits as pests in Australia - 1938
Introduced pests in Australia –
red fox, rabbit, cat, pig, & goat
Parasite effect on host population
Parasite can cause direct mortality but then can only persist in a
large host population
Usually parasite lowers host reproduction, growth or survival often this effect is indirect by way of
1) lowers host stamina - more subject to predation, competition
2) increases conspicuousness - predation risk increases
3) disorient host via neurological damage
4) alters host response to environmental stimuli
Fungal parasites alter insect behavior
Giant ant w/o and with fungus
Moose and White-tailed Deer
Deer – Moose brain worm interaction
Avian malaria occurs in areas below white
line on Island of Hawaii – highest incidence
between yellow and white lines
Hawaiian Crow – Extinct in Wild
I’iwi Honeycreeper – highly
susceptible to avian malaria
Akiapolaau Honeycreeper –
restricted to high elevation today
Amakihi Honeycreeper – shows
evidence of evolving resistance