Daily electrical activity in the master circadian clock of a diurnal mammal

Daily or circadian rhythms in mammals are orchestrated by a master circadian clock within the hypothalamic suprachiasmatic nuclei (SCN). Here, cell-autonomous oscillations in gene expression, intrinsic membrane properties, and synaptic communication shape the electrical landscape of the SCN across the circadian day, rendering SCN neurons overtly more active during the day than at night. This well-accepted hallmark bioelectrical feature of the SCN has overwhelmingly emerged from studies performed on a small number of nocturnal rodent species. Therefore, for the first time, we investigate the spontaneous and evoked electrical activity of SCN neurons in a diurnal mammal. To this end, we measured the electrical activity of individual SCN neurons during the day and at night in brain slices prepared from the diurnal murid rodent Rhabdomys pumilio and then developed cutting-edge data assimilation and mathematical modelling approaches to uncover the underlying ionic mechanisms. We find that R. pumilio SCN neurons were more excited in the day than at night, recapitulating the prototypical pattern of SCN neuronal activity previously observed in nocturnal rodents. By contrast, the evoked activity of R. pumilio neurons included a prominent suppressive response that is not present in the SCN of nocturnal rodents. Our computational modelling approaches reveal transient subthreshold A-type potassium channels as the primary determinant of the suppressive response and highlight a key role for this ionic mechanism in tuning excitability of clock neurons and optimising SCN function to accommodate R. pumilio’s diurnal niche.

KEANEKARAGAMAN JENIS MAMALIA DIURNAL DI BEBERAPA TIPE HUTAN PADA AREAL IUPHHK-HT PT. HUTAN KETAPANG INDUSTRI KABUPATEN KETAPANG

Mammals are wild animals that are often considered as pests by the community, even though the existence of mammals has an important role in the preservation of forest ecosystem as soil fertilizers, pollinators, seed dispersers, and biological bugs control. Forest is habitat for flora and fauna, but now the forests in Kalimantan are starting to be degraded caused by land clearing of plantations, illegal logging and infrastructure development. Forest degradation is very influential on forest cover, especially mammals. Land clearing by plantation companies has an impact on the survival of animals and vegetation in the plantation area. Food sources and shelter for mammals is reduced. That makes mammals move to habitats that are good vegetation and ecosystems. This study aims to record the diurnal mammal species and find out the diversity of species of mammals diumal in several forest types in the IUPHHK-HT area of PT. Hutan Ketapang Industri district Ketapang. This research was conducted on 25 February 2019 until 23 March 2019 to obtain data on species of mammals diumal in a number of forest types in the IUPHHK-HT area of PT. Hutan Ketapang Industri district Ketapang. The results of this study are expected to provide data and information on the types of diurnal mammals and the diversity of diurnal mammal species in several forest types in the IUPHHK-HT area of PT. Hutan Ketapang Industri district Ketapang The results of observations in five habitat types were found as many as 8 species belonging to 6 families. In Kerangas forest 2 species were found with 7 individuals, Peat Swamp forest was found 5 species with 15 individuals, Lowland Dipterocarpa forest was found 7 species with 19 individuals, Riparian forest was found 3 species with 9 individuals. and Open Wetlands / Flood Plains are found 3 species with a number of individuals 11.Keywords: Mammals Diumal, Diversity, Five Habitat Types