Natural Enemies and Modes of Transmission (Exam 1)

Natural Enemy

Species of consumer that reduces the fitness of its victim

Solitary Predator

Natural enemy that kills and eats alone on more than one victim

Social Predator

A natural enemy that kills and feeds in a group on more than one victim

Micro-predator

A natural enemy that feeds on but doesn't necessarily kill more than one victim

Parasitoid

A natural enemy that feeds on (infects) one host (where it develops) and kills its host as part of its development

Infect suggest an intimate prolonged interaction --> applied to forms of parasitism

Typical Parasite

A natural enemy that infects but not necessarily kill one host per life stage

Parasitic Castrator

A natural enemy that infects but not necessarily kill and block the reproduction of one host per life stage

Pathogen

A natural enemy that infects, but does not necessarily kill, one host per life stage

undergoes asexual reproduction within the host

trophically transmitted pathogen

Natural enemy that infects one host per life stage, reaching its next host by its current host being eaten.

Major axes of __________

variation separating natural enemies

Microparasites (historically defined)

viruses, bacteria, protozoans

small, short generation time, high direct reproduction rates within host (asexual)

induce immunity to reinfection --> hosts that survive initial onslaught

infection duration typically short

Macropasites (historically defined)

parasitic helminths and arthropods

much longer lifespan

Axis of _______

simple vs. complex lifestyles

Simple life cycles (SLCs)

Parasites and pathogens that require only one host species to complete their life cycle

Complex life cycles (CLCs)

More than one host species required to complete their life cycle

Hosts of CLC parasites: definitive hosts

host in which a parasite reproduces sexually

Hosts of CLC parasites: intermediate hosts

host in which a parasite develops but does not reproduce sexually

facultative micropredator

doesn't kill hosts

multiple victims during one life stage (sometimes will eat a lil...)

(also deer)

Human evolutionary history

Trophically transmitted parasitic castrator

Same parasite genus as malaria and chagas

Finishes its life cycle when the octopus eats the castrated crab

Sapronoses

parasite/organism losing its way and causing havoc in another living organism

ex. histoplasma fungus that typically reside in caves and decompose bat/bird droppings could transmit to a human and kill everything and go crazy!

Saprophage

a free living organism that consumes organic matter derived from the decomposition of dead organisms (e.g., fungi, bacteria)

sapronotic agent

a saprophage that can establish an infection, multiplying in or on a host, causing disease

Sapronosis

an infectious disease caused by a free living organism that can circumstantially infect and multiply within a host

When multiplying within a host, its progeny rarely if ever contributes to free-living population dynamics.

Host may be able to evolve resistance of the sapronotic agent is regularly encountered

Sapronoses example: brain eating amoeba :(

Naegleria fowleri

thermophilic amoeba that typically feeds on bacteria in warm freshwater bodies

can enter humans through nose --> fatal

Sapronoses example: white nose syndrome

Pseudogymnoascus destructans --> Closest relative are all saprophages

P. destructans seems to be less of an effective saprophage than its congeners.

Likely introduced to northeastern US from Europe in 2006.

Rapid spread and millions of bat deaths

All feed on decaying cave materials (guano)

Evolution of obligate parasitism occurring?

One isolate from NA

Anthroponosis

an infectious disease primarily transmitted between humans

Sometimes can be transmitted from humans to other animals

Ex. Measles - Extremely contagious

Zoonosis

an infectious disease that can be transmitted from non human animals to human host; primary host is a non human animal

ex. Sin Nombre Virus

- hantavirus

- Typically a virus of deer mice; can be transmitted to humans from aerosolized virus from mouse excreta

vertical transmission

Transmission from parents to offspring

Ex. many lice (featherlice) are vertically transmitted

Direct contact transmission - infected host must contact an uninfected host to transmit the parasite

Direct passive transmission (vertical)

cyst, spore, or egg must contact or ingested by host

Ex. whipworm in humans (soil contaminated food or hands)

Direct active transmission (vertical)

host seeking free-living parasite stage that infects a host

Ex. hookworm caused by various nematodes

Direct contact transmission (vertical)

Infected host must contact an uninfected host to transmit the parasite

Ex. the flu

Horizontal transmission

Transmission between individuals other than parents to offspring

Far more common transmission

Vector transmission (horizontal/indirect)

a host species (typically an arthropod) transmits the parasite to different host species (often by biting)

Trophic transmission (horizontal/indirect)

a predator host becomes infected by killing and consuming a prey host

Efficiency of Transmission Strategies

How to overcome low efficiency? --> larger number of infected parasites

Competence

the capacity of a host to transmit infection after being exposed to a parasite

Competence and exposure (contact between host and parasite) are continuous variables and together determine transmission

Dead end host

hosts that are not competent at all

Ex. humans are dead-end hosts for T. gondii. (