Ibrahim Magdy Hegab

Introduction Embryonic development and growth rate of avian chicks are influenced by environmental circumstances during incubation. The rate and quality of embryonic growth until hatch depends on various external factors such as temperature,

Around the world, climate change has impacted many species. In this study, we used bioclimatic variables and biophysical layers of Central Asia and the Asian Highlands combined with presence data of brown bear (Ursus arctos) to understand their current distribution and predict their future distribution under the current rate of climate change. Our bioclimatic model showed that the current suitable habitat of brown bear encompasses 3,430,493 km² in the study area, the majority of which (>65%) located in China. Our analyses demonstrated that suitable habitat will be reduced by 11% (378,861.30 km²) across Central Asia and the Asian Highlands by 2,050 due to climate change, predominantly (>90%) due to the changes in temperature and precipitation. The spatially averaged mean annual temperature of brown bear habitat is currently −1.2°C and predicted to increase to 1.6°C by 2,050. Mean annual precipitation in brown bear habitats is predicted to increase by 13% (from 406 to 459 mm) by 2,050. Such changes in two critical climatic variables may significantly affect the brown bear distribution, ethological repertoires, and physiological processes, which may increase their risk of extirpation in some areas. Approximately 32% (1,124,330 km²) of the total suitable habitat falls within protected areas, which was predicted to reduce to 1,103,912 km² (1.8% loss) by 2,050. Future loss of suitable habitats inside the protected areas may force brown bears to move outside the protected areas thereby increasing their risk of mortality. Therefore, more protected areas should be established in the suitable brown bear habitats in future to sustain populations in this region. Furthermore, development of corridors is needed to connect habitats between protected areas of different countries in Central Asia. Such practices will facilitate climate migration and connectivity among populations and movement between and within countries.

Effects of different durations of fasting/re-feeding bouts on growth, biochemical and histological changes in the digestive tract of Ganus golden trout (Oncorhynchus mykiss) | Xia Liu, Ibrahim Magdy Mohamed Hegab, Junhu Su, Xiaohua Du, Xiping Fan, Qiong Zhang, Yuan Gao, Haifang Wang | Agricultural Journals

Sexual dimorphism is prevalent in most living organisms. The difference in size between sexes of a given species is generally known as sexual size dimorphism (SSD). The magnitude of the SSD is determined by Rensch's rule where size dimorphism increases with increasing body size when the male is the larger sex and decreases with increasing average body size when the female is the larger sex. The unique underground environment that zokors (Eospalax baileyi) live under in the severe habitat of the Qinghai‐Tibetan Plateau (QTP) could create SSD selection pressures that may or may not be supported by Rensch's rule, making this scientific question worthy of investigation. In this study, we investigated the individual variation between sexes in body size and SSD of plateau zokors using measurements of 19 morphological traits. We also investigated the evolutionary mechanisms underlying SSD in plateau zokors. Moreover, we applied Rensch's rule to all extant zokor species. Our results showed male‐biased SSD in plateau zokors: The body‐ and head‐related measurements were greater in males than in females. Linear regression analysis between body length, body weight, and carcass weight showed significant relationships with some traits such as skull length, lower incisor length, and tympanic bulla width, which might support our prediction that males have faster growth rates than females. Further, the SSD pattern corroborated the assumption of Rensch's rule in plateau zokors but not in the other zokor species. Our findings suggest that the natural underground habitat and behavioral differences between sexes can generate selection pressures on male traits and contribute to the evolution of SSD in plateau zokors.

| The objective of the current study was to estimate the relationship between endogenous serum testosterone hormones and agonistic behavior in male Japanese quail. Forty healthy adult Japanese quails (30 males and 10 females) were randomly distributed into three experimental groups. The 1 st group (G 1 , n= 10 males) was housed individually, the 2 nd group (G 2 , 10 males and 10 females) was simultaneously housed in one cage, and the 3 rd group (G 3; n= 10 males) birds were housed together in a single cage. Serum testosterone concentration has been estimated alongside different behavioral (head banging, eyelid injuries, head plumage deterioration) and sexual (cloacal gland area, foam production, absolute and relative testes weight) traits. The results revealed that there was a highly significant difference ( p ≤0.001) among males housing status on testosterone levels. Serum concentrations of testosterone were significantly ( p ≤0.001) increased in males in G 2 and G 3 by 91.35 and 98.41 %, respectively than that of males in G 1 . In addition, the results demonstrated that highly positive correlations ( p =0.01) were found between serum testosterone concentration and each of head banging, eyelid injuries and head plumage deterioration, and moderate positive correlations ( p =0.225) with foam production. In contrast, negative correlations were found between testosterone concentration and each of absolute testes weight ( p =0.294), and cloacal gland area ( p =0.074). These results demonstrate that changing levels of testosterone in the blood may be due to male’s status. The present results may provide a role of testosterone towards aggressive pecking behavior among males when kept lonely or with females.