The feeding habits of six pelagic and predatory teleosts in eastern Cape coastal waters (South Africa)

A four-year study of the feeding habits of six pelagic teleost species in eastern Cape coastal waters of South Africa is analysed. These predators are Lichia amia, Pomatomus sallatrix, Seriola lalandi, Atractoscion aequidens, Katsuwonus pelamis and Thunnus albacares. All species occur in inshore coastal water (< 1 -8 km from shore) for at least part of the year. The tunas were also sampled from the edge of the continental shelf (40–50 km from shore). The use of squid 'beaks' and fish otoliths allowed accurate prey identification and size estimates. Variations in prey taken are attributed to differences in locality, predator species and size. Three pelagic fish species are important to all the predators: Sardinops ocettata, Etrumeus teres and Engraulis capensis. The inshore squid, Loligo reynaudi, is another major prey item. Offshore tuna samples revealed a different prey spectrum, viz. oceanic squid and saury, Scomberesox saurus, being taken frequently.     

Daily rhythms of Fos expression in hypothalamic targets of the suprachiasmatic nucleus in diurnal and nocturnal rodents.

Little is known about the differences in the neural substrates of circadian rhythms that are responsible for the maintenance of differences between diurnal and nocturnal patterns of activity in mammals. In both groups of animals, the suprachiasmatic nucleus (SCN) functions as the principal circadian pacemaker, and surprisingly, several correlates of neuronal activity in the SCN show similar daily patterns in diurnal and nocturnal species. In this study, immunocytochemistry was used to monitor daily fluctuations in the expression of the nuclear phosphoprotein Fos in the SCN and in hypothalamic targets of the SCN axonal outputs in the nocturnal laboratory rat and in the diurnal murid rodent, Arvicanthis niloticus. The daily patterns of Fos expression in the SCN were very similar across the two species. However, clear species differences were seen in regions of the hypothalamus that receive inputs from the SCN including the subparaventricular zone. These results indicate that differences in the circadian system found downstream from the SCN contribute to the emergence of a diurnal or nocturnal profile in mammals.