Endocrine Control of Lamprey Reproduction and Management Implications

The hypothalamic-pituitary (HP) system is considered to be a vertebrate innovation and seminal event that emerged prior to or during the differentiation of the ancestral agnathans and led to the neuroendocrine control of many complex functions including growth, reproduction, osmoregulation, stress and metabolism (Sower et al., 2009). We will report on some of our latest findings from the lamprey genome that includes the identification of lamprey(l) GnRH-II, two novel GnRH receptors (lGnRHR-2 and GnRHR-3), and gonadotropin-inhibiting hormone/lamprey RFamide and its related peptides (RP-1 and RP-2), lRFa-1 (18 aa), lRFa-1 (22 aa) and lRFa-2. From our comparative functional studies on these neuroendocrine peptides and respective receptors we propose that the lamprey can serve as a model for analysis of the evolutional mechanisms leading to emergence of the highly specialized gnathostome endocrine axis. Controlling reproduction either by improving efficiency or preventing population increases in commercially important and non-indigenous species, respectively, is of key importance to farmers and fish and wildlife biologists.  To control reproduction, it is critical to understand the underlying mechanisms of neuroendocrine control. In all vertebrates, GnRH is the “master or central control” of reproduction, and has provided the focus of decades of concerted and intensive research that has led to the development of current treatments for infertility, cancers of the reproductive system and for use in agriculture/aquaculture. We will delineate how these neuroendocrine findings can lead to the development of novel strategies for improving and controlling reproduction in fish. These underlying mechanisms of neuroendocrine control are likely conserved across vertebrates; therefore the information gained from these studies will likely be applicable to other cultured fish. This research was funded by  NSF IOS-0849569, NIH 5R21RR024477-02 and NH Agricultural Experiment Station H-332.