Behavior-altering parasite

Parasites that alter the behavior of their hosts

Behavior-altering parasites

Leucochloridium paradoxum in a snail

Behavior-altering parasites are organisms that can manipulate the behavior of their hosts to increase their own chances of transmission or reproduction. These parasites can affect a wide range of hosts, including insects, mammals, and even humans. The mechanisms by which they alter behavior are diverse and can include changes in the host's nervous system, hormonal balance, or immune response.

Mechanisms of behavior alteration

Parasites can alter host behavior through several mechanisms:

• Neurotransmitter manipulation: Some parasites can produce chemicals that mimic or interfere with the host's neurotransmitters, leading to changes in behavior. For example, the protozoan Toxoplasma gondii can alter the behavior of rodents, making them less fearful of predators such as cats.

• Hormonal changes: Parasites can also affect the hormonal balance of their hosts. This can lead to changes in behavior that benefit the parasite. For instance, some parasitic wasps inject hormones into their hosts to manipulate their development and behavior.

• Immune system interaction: By interacting with the host's immune system, parasites can induce changes in behavior. This can include altering the host's feeding habits or social interactions.

Examples of behavior-altering parasites

Leucochloridium paradoxum

Leucochloridium paradoxum in a snail

The flatworm Leucochloridium paradoxum infects snails and alters their behavior to increase its chances of being eaten by birds, its definitive host. The parasite causes the snail's tentacles to pulsate and resemble caterpillars, attracting birds.

Horsehair worms

Horsehair worm emerging from a cricket

Horsehair worms, or Nematomorpha, are known to manipulate their insect hosts, such as crickets, to jump into water, where the adult worms can emerge and reproduce.

Emerald cockroach wasp

Emerald cockroach wasp dragging a cockroach

The emerald cockroach wasp, or Ampulex compressa, injects venom into a cockroach, turning it into a "zombie" that can be led to the wasp's burrow, where it serves as food for the wasp's larvae.

Dinocampus coccinellae

Ladybird with a parasitoid cocoon

The parasitic wasp Dinocampus coccinellae lays its eggs inside ladybirds. The developing larvae manipulate the ladybird to guard the cocoon until the wasp emerges.

Reclinervellus nielseni

Reclinervellus nielseni

Reclinervellus nielseni is a wasp that manipulates its spider host to build a special web that protects the wasp's cocoon from rain and predators.

Toxoplasma gondii

Toxoplasma gondii cysts

Toxoplasma gondii is a protozoan parasite that can infect most warm-blooded animals, including humans. It is known to alter the behavior of rodents, reducing their fear of predators, which facilitates transmission to the parasite's definitive host, the cat.

Impact on ecosystems and human health

Behavior-altering parasites can have significant impacts on ecosystems by influencing the population dynamics of their hosts and altering predator-prey relationships. In humans, parasites like Toxoplasma gondii have been studied for potential links to changes in behavior and mental health, although the extent of these effects is still under investigation.

Related pages

• Parasitism
• Neuroparasitology
• Host manipulation by parasites