Seasonal spermatogenesis in the mute swan (Cygnus olor).
D000818:Animals; D001717:Birds / Q000033:anatomy & histology / Q000502:physiology*; D008297:Male; D012621:Seasons; D012671:Seminiferous Tubules / Q000648:ultrastructure; D012708:Sertoli Cells / Q000502:physiology; D013091:Spermatogenesis; D013094:Spermatozoa / Q000502:physiology