title: Ovarian activity is differentially regulated across the breeding season in immature compared with adult American crows (Corvus brachyrhynchos).
abstract: American crow (Corvus brachyrhynchos) reproduction is seasonal. While photoperiod alters reproductive physiology and behavior in nesting adults, whether seasonal photoperiod changes alter ovarian activity in nonnesting adult and immature birds was not known. Ovarian follicular composition was examined in immature and nonnesting adult crows. Birds were divided into groups reflecting daylight hour exposure when captured: 12L, 12:30L, 13:30L, and 14L, representing early-, progressing-, peak-, and postbreeding seasons in southern California. Adult ovarian mass peaked in 13:30L and then decreased 65% by 14L. In contrast, immature ovarian mass peaked in 12L and decreased 58% by 14L. Whereas no change in adult follicle composition occurred, primordial follicle numbers increased 42%, and previtellogenic follicles increased 86% in immatures, resulting in an overall follicle number increase in immatures by 13:30L and 14L. Adult atretic follicles declined 68% by 14L, while immature atretic follicle numbers remained constant. Adult apoptotic transferase-mediated dUTP nick end labeling (TUNEL)-positive follicle numbers remained constant until a 52% decrease occurred in 13:30L. TUNEL-positive follicles declined 58% by 12:30L among immatures. These data are the first to demonstrate that follicular composition is differentially regulated between nonnesting adult and immature American crows. Seasonal ovarian activity alterations in nonbreeding adults may serve to prime individuals for potential mating.
authors.affiliation: Department of Biological Sciences, California State University, Long Beach, California 90840, USA.
authors.forename: Coventry O
authors.initials: CO
authors.lastname: Dougherty
authors.forename: Wallace L
authors.initials: WL
authors.lastname: Ross
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Young
mesh_terms: D000818:Animals; D001947:Breeding; D046368:Crows / Q000502:physiology*; D005260:Female; D010053:Ovary / Q000033:anatomy & histology / Q000502:physiology*; D012621:Seasons; D012741:Sexual Maturation / Q000502:physiology*; D013997:Time Factors