Meeting Abstract
Adipokinetic hormone (AKH) is a multifunctional neuropeptide in the gonadotropin-releasing hormone superfamily. In insects, AKH primarily acts to mobilize energy stores during times of high energetic demand, but it has been shown to have other effects. Data mining has recently shown the presence of AKHs within the lophotrochozoa, however, they remain poorly characterized. We have previously identified an AKH in an intertidal gastropod mollusk, the California sea hare (Aplysia californica), and named it ac-AKH. Our previous data showed ac-AKH induced acute weight loss, suggesting a role in volume regulation. The overarching goals of this study were to test the role of ac-AKH as a volume regulator and examine the mechanism by which ac-AKH induced the acute weight loss. Our results showed that ac-AKH reduced body mass, in part, through the reduction of hemolymph volume without altering hemolymph osmolality or specific osmolytes. The effect of ac-AKH on volume loss was enhanced by acclimation to a hyposaline condition. We further showed that ac-akh expression in a central ganglion was inhibited during a hyposaline challenge, and that the administration of ac-AKH partially reversed the increase in body mass, but not the hemolymph osmolality change, caused by a hyposaline challenge. These data collectively show that ac-AKH acts to regulate hemolymph volume, but not hemolymph osmolality, in A. californica. Importantly, our results highlight the functional divergence of this structurally conserved neuropeptide in the molluscan lineage.
