Meeting Abstract

140.3  Monday, Jan. 7  The effect of food availability on the seasonal reproductive development of birds DAVIES, S*; DEVICHE, P; Arizona State University; Arizona State University scott.davies@asu.edu

Birds use food availability to synchronize seasonal reproductive activity with local environmental conditions, but the mechanism(s) by which this cue affects the hypothalamus‐pituitary‐gonadal (HPG) axis remain(s) poorly understood. We examined the effect of food availability on the HPG axis of adult male Abert’s Towhees, Melozone aberti. We exposed captive birds to long days to stimulate reproductive development and assigned them to one of three groups: ad lib food, restricted food availability, in which they received 70% of ad lib consumption for four weeks, or two weeks of food restriction followed by two weeks of ad lib food. Two weeks of food restriction decreased body mass, furcular fat, and pectoral muscle. Food availability had no effect on the number, area, or optical density of gonadotropin‐releasing hormone (GnRH-I) cell bodies, or the optical density of GnRH-I fibers in the median eminence (ME). Treatment also had no effect on the number or optical density of gonadotropin‐inhibitory hormone (GnIH) cell bodies, or the optical density of ME GnIH fibers. However, the area of GnIH cell bodies was largest in ad lib birds and smallest in food restricted birds. Although paired testis masses and seminiferous tubule diameters were similar across groups, plasma testosterone (T) levels were higher in ad lib birds than in food restricted or reinstated ad lib birds, and there was no difference between food restricted and reinstated ad lib birds. The width of the cloacal protuberance (CP; an androgen-sensitive secondary sexual characteristic) was a function of food availability, with food restriction decreasing CP width and reinstating ad lib food increasing CP width. Thus, food availability affected the HPG axis, but this influence was specific to some components of the axis. Specifically, food restriction may affect the HPG axis by increasing GnIH secretion and decreasing T secretion.