Reproductive seasonality of the female Florida gar, Lepisosteus platyrhincus

Abstract

Our objective was to characterize the reproductive seasonality of a wild population of female Florida gar, Lepisosteus platyrhincus. We measured the gonadosomatic index, plasma estradiol, testosterone, and vitellogenin concentrations, and follicle diameters of fish collected from Orange Lake, Florida (USA). Additionally, the reproductive stage of the ovary was resolved histologically. We observed a seasonal pattern in reproduction. Following a quiescent period in the summer, there was an increase in sex steroid hormones during the fall, associated with the onset of vitellogenesis and active oogenesis. During the February collection, we directly observed ovulation in several females. This observation was supported by a sharp decrease in the gonadosomatic index between February and March as well as a decline in plasma hormones to basal levels during the summer months. Our data suggest the Florida gar has a group-synchronous ovary and the majority of females spawned during the early spring, followed by a general decrease in reproductive parameters to summer levels. While hormone and vitellogenin peaks may vary annually and variations in these reproductive patterns are expected for different collection sites, this study is important as it is the first characterization of the seasonal morphological and endocrinological reproductive pattern in a female holostean species. Moreover, it increases our understanding of basic reproductive biology of semitropical fishes in general, and nonteleost, bony fishes in particular.