霊長類とシラミの関係

抄録

The relationship between primates and lice is discussed. Lice are ectoparasites that live on the body surface of mammals and, in contrast to ticks and fleas, do not leave the host during their life cycle. Host mammals may experience adverse effects from lice, such as anemia and skin irritation. Moreover, lice are vectors of infectious diseases; for example, human lice (Pediculus humanus) transmit the epidemic typhus pathogen between humans (Homo sapiens). DDT virtually eliminated human lice in several countries after World War II. Early Japanese primatologists who began research during this period had little interest in the relationship between primates and lice. Primates groom each other to remove lice, ticks, and small objects. Prosimians use their lower incisors to groom, similar to rodents and African antelopes, whereas anthropoids, which have a retinal fovea with high visual acuity and functional fingers that allow them to find and pick small ectoparasites from the body surface, groom using their hands and mouth. Japanese monkeys (Macaca fuscata) and lice (Pedicinus obtusus, P. eurygaster) have an entwined host-parasite and predator-prey relationship. Lice lay nits on monkeys, who are hosts, in areas where hair growth is dense because the hair conceals nits from the monkeys, who are their predators. Monkeys remove and eat nits according to nit density. Given the high intrinsic rate of natural increase in lice, monkeys need to groom daily. This necessity may explain why monkeys live with grooming partners making social groups. The development of simplified techniques to estimate louse infection in primates will advance the study of socioecological models and lice infection dynamics in primate metapopulations.