The effect of different ambient temperatures on local sympathetic activity in rats

İki grup halinde yapılan deneylerde (5 ve 16 - saat) Wistar-Albino sıçanlar (200-260 gr) 5°C, 20°C, 36°C ve 42°C lerde tutularak idrarlarındaki katekolamin miktarı saptandı. Katekolamin yöntem tayini, idrardaki katekolaminleri uygun PH da alüminyum okside bağlamak ve sonra geri alarak okside edip, oksidasyon sırasında açığa çıkan fluoresans şiddetini spectrafotofluorometre'de ölçmek esasına dayanmaktadır. Bulgularımızda 5 saat 42°C lik ortamda tutulan sıçanların idrar miktarları, kontrol grubu olarak çalıştığımız 20°C lik ortamda tutulan sıçanların katekolamin miktarlarından yüksek bulundu. Aynı koşullarda 16 saat 5°C ve 42°C de tutulan sıçanların idrarlarındaki katekolamin miktarında da benzer oranda artış görüldü. Sarnıç olarak ısının, sıçanlarda sempatik sistemi, etkileyerek strese yol açtığı ve stresin de katekolamin miktarını arttırdığı düşünüldü

Foraging behaviour and habitat use by brown skuas Stercorarius lonnbergi breeding at South Georgia

Top predators are critical to ecosystem function, exerting a stabilising effect on the food web. Brown skuas are opportunistic predators and scavengers. Although skuas are often the dominant land-based predator at seabird colonies, this is the first detailed study of their movements and activity during breeding. The study was carried out at Bird Island, South Georgia (54°00′S, 38°03′W), in the austral summer of 2011/2012 and included GPS data from 33 breeding adults tracked during the late incubation and early chick-rearing periods. Brown skuas spent on average more than 80 % of time in the territory, and it was extremely rare for both partners to leave the territory simultaneously. Much more time was spent foraging at the coast than in penguin colonies and, based on saltwater immersion data, adults never foraged at sea. None of the tracked birds appeared to specialise in catching small petrels at night. Fewer foraging trips were made per day, and hence, more time was spent in the territory, during incubation than chick-rearing. Despite the pronounced sexual size dimorphism, there were no effects of sex on territorial attendance, foraging time or habitat use. Skuas at Bird Island show higher territorial attendance and are less likely to leave the territory unattended than those breeding elsewhere, suggesting closer proximity to more diverse or abundant food resources than at other colonies. The results tie in with previous diet studies, indicating that brown skuas at this site feed mostly on seal placentae and carrion and that birds may rely on a broader range of food resources as the season progresses