Chronic kisspeptin administration stimulated gonadal development in pre-pubertal male yellowtail kingfish (Seriola lalandi; Perciformes) during the breeding and non-breeding season

The kisspeptin system is now accepted as a key regulator of vertebrate reproductive function, particularly the onset of puberty. In teleosts, the stimulatory effect of exogenous kisspeptins has been demonstrated mainly at the hypothalamic and pituitary levels of the reproductive axis, with very limited information pertaining to gonadal response. We determined the effect of chronic peripheral administration of the conserved kisspeptin decapeptides (YNLNSFGLRY or Kiss1-10; and FNFNPFGLRF or Kiss2-10) on gonadal development of pre-pubertal yellowtail kingfish (Seriola lalandi), a Perciform teleost, during the breeding and non-breeding season. We utilized slow-release implants to chronically deliver the synthesized peptides, which were based on the yellowtail kingfish kiss1 and kiss2 cDNA sequences that we isolated. The expression level of kiss2r and gnrh1 in the brain or hypothalamus did not vary between treated and control groups. Pituitary expression of fshβ and lhβ was upregulated only with Kiss1-10 treatment regardless of the season. Based on histological evidence, gonadal development was stimulated in male fish with either Kiss1-10 or Kiss2-10, with Kiss2-10 being more effective during the non-breeding period. Overall, our results suggest that kisspeptins modulate the early gonadal development of male yellowtail kingfish, however that may vary with the breeding season.