This scarcity of evidence in general may reflect a lack of studies where this has been explicitly Pazopanib CAS investigated. Box 2. Examples of Parasites That Are Adapted to One Sex of the Host The idea that parasite populations can adapt to only one of the sexes of their host or diverge to adapt to both host sexes is novel, and sex differences in infection success and/or symptoms have not been interpreted (or analyzed) from this perspective. While, to our knowledge, no example of a host sex�Cspecific dimorphism has been described as such, some known parasite adaptations may correspond to single-sex specializations or plastic sex-specific disease expression (as described in the main text). Here, we refer to some examples that illustrate different aspects of parasite adaptation to host sex.

There are many parasites that exploit either exclusively or predominantly only one sex of their hosts. Some of these have evolved mechanisms for discriminating between the sexes, thus ensuring they only infect suitable individuals. Others have evolved mechanisms for manipulating the infected host so as to recover particular sex-specific traits necessary for parasite proliferation and/or transmission. Discriminating the Sex of the Host Myxozoa belonging to the genera Kudoa are myxosporean parasites of fish that comprise around 70 species [81], of which all but one infect multiple hosts tissues. The only exception is the species Kudoa ovivora, which specifically infects the host’s ovaries [49]. Curiously, to our knowledge, this parasite is the only species of the genus that infects exclusively sequential hermaphrodites where fish develop first as female and then become male (e.

g., labrids and scarids). Such fish populations are known to have female-biased sex ratios [21], which could explain that this parasite adapted specifically to the characteristics of female hosts. The relevance of host sex ratio for parasite single-sex specialization is further discussed in the main text. The ectoparasitic mite Spinturnix andegavinus (Figure 3B) is mainly transmitted among ��maternity clusters�� of its host, the bat Myotis daubentoni (Figure 3A). Experimental studies have shown that these mites are capable of growing only on female hosts [82], which necessarily means that they are specifically adapted to this host type.

The same studies also revealed that the parasite actively chooses to attach to females [82], and that selection for being Cilengitide on the correct host was sufficiently strong to favor mechanisms (possibly via sense organs) for the parasite to discriminate between host sexes. Many endo- and ectoparasites are known to be able to actively choose between host species [83]�C[88], and even between host individuals of the same species [89]. It might be possible that host sex discrimination is more widespread than is commonly believed.