title: An Extraordinary Host-Specific Sex Ratio in an Avian Louse (Phthiraptera: Insecta)--Chemical Distortion?
abstract: Distortions of sex ratios and sexual traits from synthetic chemicals have been well documented; however, there is little evidence for such phenomena associated with naturally occurring chemical exposures. We reasoned that chemical secretions of vertebrates could contribute to skewed sex ratios in ectoparasitic insects due to differences in susceptibility among the sexes. For example, among ectoparasitic lice the female is generally the larger sex. Smaller males may be more susceptible to chemical effects. We studied sex ratios of lice on two sympatric species of colonial seabirds. Crested auklets (Aethia cristatella) secrete a strong smelling citrus-like odorant composed of aldehydes while a closely related congener the least auklet (Aethia pusilla) lacks these compounds. Each auklet hosts three species of lice, two of which are shared in common. We found that the sex ratio of one louse species, Quadraceps aethereus (Giebel), was highly skewed on crested auklets 1:69 (males: females), yet close to unity on least auklets (1:0.97). We suggest that a host-specific effect contributes to this difference, such as the crested auklet's chemical odorant.
authors: Institute of Marine Science, University of Alaska, Fairbanks, AK 99775. Current address: Science Department, College of Rural and Community Development, Kuskokwim Campus, University of Alaska, Bethel, AK 99559. hector.douglas@alaska.edu.
authors: H D
authors: HD
authors: Douglas
authors: Department of Biology, University of Utah, Salt Lake City, UT 84412.
authors: J R
authors: JR
authors: Malenke
mesh_terms: D000413:Alaska / Q000453:epidemiology; D000447:Aldehydes / Q000378:metabolism*; D000818:Animals; D046091:Charadriiformes / Q000378:metabolism; D058507:Host Specificity; D058326:Ischnocera / Q000502:physiology; D010373:Lice Infestations / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D009812:Odorants / Q000032:analysis*; D012744:Sex Ratio
chemical_list: D000447:Aldehydes
keywords: aldehyde; lice; seabird; sex ratio distortion