Endoparasitism and ectoparasitism have advantages and disadvantages

There are advantages and disadvantages to living in or on a host (TABLE 13.1). Because ectoparasites live on the surface of their host, it is relatively easy for them or their offspring to disperse from one host individual to another.

It is much more difficult for endoparasites to disperse to new hosts. Endoparasites solve this problem in a variety of ways. Some, like the enslaver parasites discussed in the Case Study at the opening of this chapter, alter the physiology or behavior of their host in ways that facilitate their dispersal. Other examples include the bacterium Vibrio cholerae, which causes cholera, and the amoeba Entamoeba histolytica, which causes amoebic dysentery. People with cholera and dysentery have diarrhea, a condition that increases the chance that the parasite will contaminate drinking water and thereby spread to new hosts. Other endoparasites have complex life cycles that include stages that are specialized for dispersing from one host species to another (see Figure 13.9).

TABLE 13.1 Advantages and Disadvantages of Living in or on a Host

	Ectoparasitism	Endoparasitism

Advantages	Dispersal easier	Feeding easier
	Safer from host's immune system	More protection from external environment
Disadvantages	Feeding more difficult	Dispersal more difficult
	Greater exposure to external environment	Greater vulnerability to host's immune system
	Greater vulnerability to natural enemies

Although dispersal is relatively easy for ectoparasites, there are costs to life on the surface of a host. Compared with endoparasites, ectoparasites are more exposed to natural enemies such as predators, parasitoids, and parasites.

Aphids, for example, are attacked by ladybugs, birds, and many other predators, as well as by lethal parasitoids and by parasites such as mites that suck fluids from their bodies. Endoparasites, in contrast, are safe from all but the most specialized predators and parasites. Endoparasites are also relatively well protected from the external environment, and they have relatively easy access to food—unlike an ectoparasite, an endoparasite does not have to pierce the host's protective outer surfaces to feed. But living within the host does expose endoparasites to a different sort of danger: more exposure to the host's immune system. Some parasites have evolved ways to tolerate or overcome immune system defenses, as we will see in the following section.

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Source: Bowman W., Hacker S.. Ecology. 6th ed. — Oxford University Press,2023. — 744 p.. 2023

Endoparasitism and ectoparasitism have advantages and disadvantages

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