title: Are secondary sex traits, parasites and immunity related to variation in primary sex traits in the Arctic charr?
abstract: Primary and secondary sex traits are influenced by the same sex hormones, and the expression of secondary sex traits may consequently signal males' capacity for sperm production. Sperm quality may also be influenced by immune activity, as sperm are non-self to the male. Parasite infections alter immune activity and may thus reduce ejaculate quality. In the Arctic charr (Salvelinus alpinus) the red abdominal colour is considered an ornament that signals important information in mate choice. We captured and individually caged sexually mature male Arctic charr during the spawning period. Afterwards we estimated abdominal colour, parasite infections, gonad mass and several spermatological and immunological variables. Intensity of abdominal colour was positively correlated to testes mass, milt mass and sperm cell numbers produced. Additionally, males with low parasite intensities had high testes mass and produced milt with high sperm density, indicating a trade-off between parasite resistance and development of primary sex traits. Our measures of immunity were, however, not related to primary sex traits. We conclude that females evaluating male abdominal coloration may obtain information about differences between males in fertilization potential and parasite resistance.
authors.affiliation: Department of Evolution and Ecology, Institute of Biology, Faculty of Science, University of Tromsø, 9037 Tromsø, Norway.
authors.forename: Marthe
authors.initials: M
authors.lastname: Måsvaer
authors.forename: Ståle
authors.initials: S
authors.lastname: Liljedal
authors.forename: Ivar
authors.initials: I
authors.lastname: Folstad
mesh_terms: D000818:Animals; D001837:Body Weights and Measures; D005260:Female; D006098:Granulocytes; D008214:Lymphocytes / Q000097:blood; D008297:Male; D009664:Norway; D010271:Parasites / Q000502:physiology*; D010858:Pigmentation / Q000502:physiology; D025341:Principal Component Analysis; D012727:Sex Characteristics; D013094:Spermatozoa / Q000502:physiology*; D013737:Testis / Q000502:physiology; D014337:Trout / Q000276:immunology / Q000469:parasitology / Q000502:physiology*