Diving behavior and movements of juvenile hawksbill turtles Eretmochelys imbricata on a Caribbean coral reef

Abstract As historically abundant spongivores, hawksbill turtles Eretmochelys imbricata likely played a key ecological role on coral reefs. However, coral reefs are now experiencing global declines and many hawksbill populations are critically reduced. For endangered species, tracking movement has been recognized as fundamental to management. Since movements in marine vertebrates encompass three dimensions, evaluation of diving behavior and range is required to characterize marine turtle habitat. In this study, habitat use of hawksbill turtles on a Caribbean coral reef was elucidated by quantifying diel depth utilization and movements in relation to the boundaries of marine protected areas. Time depth recorders (TDRs) and ultrasonic tags were deployed on 21 Cayman Islands hawksbills, ranging in size from 26.4 to 58.4 cm straight carapace length. Study animals displayed pronounced diel patterns of diurnal activity and nocturnal resting, where diurnal dives were signiWcantly shorter, deeper, and more active. Mean diurnal dive depth ( §SD) was 8 § 5 m, range 2-20 m, mean nocturnal dive depth was 5 § 5 m, range 1-14 m, and maximum diurnal dive depth was 43 § 27 m, range 7-91 m. Larger individuals performed signiWcantly longer dives. Body mass was signiWcantly correlated with mean dive depth for nocturnal but not diurnal dives. However, maximum diurnal dive depth was signiWcantly correlated with body mass, suggesting partitioning of vertical habitat by size. Thus, variable dive capacity may reduce intraspeciWc competition and provide resistance to degradation in shallow habitats. Larger hawksbills may also represent important predators on deep reefs, creating a broad ecological footprint over a range of depths

Epigenetic modulation of adult hippocampal neurogenesis by extremely low-frequency electromagnetic fields.

Throughout life adult neurogenesis generates new neurons in the dentate gyrus of hippocampus that have a critical role in memory formation. Strategies able to stimulate this endogenous process have raised considerable interest because of their potential use to treat neurological disorders entailing cognitive impairment. We previously reported that mice exposed to extremely low-frequency electromagnetic fields (ELFEFs) showed increased hippocampal neurogenesis. Here we demonstrate that the ELFEF-dependent enhancement of hippocampal neurogenesis improves spatial learning and memory. To gain insights on the molecular mechanisms underlying ELFEFs\u2019 effects we extended our studies to an in vitro model of neural stem cells (NSCs) isolated from the hippocampi of newborn mice. We found that ELFEFs enhanced proliferation and neuronal differentiation of hippocampal NSCs by regulation of epigenetic mechanisms leading to pro-neuronal gene expression. Upon ELFEF stimulation of NSCs, we observed a significant enhancement of expression of the pro-proliferative gene Hes1 and the neuronal determination genes NeuroD1 and Neurogenin1. These events were preceded by increased acetylation of H3K9 and binding of the phosphorylated transcription factor cAMP response element-binding protein (CREB) on the regulatory sequence of these genes. Such ELFEF-dependent epigenetic modifications were prevented by the Cav1-channel blocker nifedipine, and were associated with increased occupancy of CREB binding protein (CBP) to the same loci within the analyzed promoters. Our results unravel the molecular mechanisms underlying the ELFEFs\u2019 ability to improve endogenous neurogenesis, pointing to histone acetylation\u2013related chromatin remodeling as a critical determinant. These findings could pave the way to the development of novel therapeutic approaches in regenerative medicin