AHR is a transcription factor that is activated by the ligand. Two amino acid residues (Ile_Ser as high sensitivity, Ile_Ala as moderate sensitivity, and Val_Ala as low sensitivity) corresponding to the 324th and 380th positions in the ligand binding domain (LBD) of the chicken AHR1, could be an important factor determining susceptibility to dioxin in avian species. This study showed that ecological factors have driven natural selection pressures on the avian AHR genotypes in the evolutionary process. The association between ecological factors and avian AHR1 LBD genotypes was statistically analyzed. This paper reviews that combinations of certain ecological factors and differential sensitivity to DLCs in avian species could have enforced natural selection pressure on AHR1 genotypes in birds.

　Chlorinated dioxins and related compounds (DRCs) have been found in a variety of environmental matrices, due mainly to their high persistence and bioaccumulation. The regulation on DRCs emission in Japan has been introduced under the “Law Concerning Special Measures against Dioxins” implemented in 1999. Since 1998, the Ministry of the Environment has conducted a nationwide project “Survey on the State of Dioxins Accumulation in Wildlife” in order to understand contamination status and verify effectiveness in the regulation policies. As a part of this project, we investigated contamination status and effects of DRCs in common cormorants (Phalacrocorax carbo) and black-eared kites (Milvus migrans) collected from Lake Biwa and the Kanto district in Japan, respectively. Results showed that DRCs contamination was pronounced in cormorants. In contrast, DRC levels in kites were relatively low. We found congener-specific features of DRCs for hepatic sequestration, maternal transfer through egg-laying, and growth stage-dependent accumulation. In the cormorant liver, expression of cytochrome P450 1A (CYP1A) was induced by DRCs. The present study, together with the whole nationwide projects, showed that while there was a clear decline of the DRCs emission in Japan from the late 1990s as an outcome of the national regulation, tissue levels of DRCs in wild animals were fairly constant over time. Hence, there is a need for a continuous longitudinal monitoring study for accumulation of DRCs and their effects in wildlife.

　Nowadays, chemical hazards in bird have been reported worldwide, and above all, anticoagulant rodenticides for vertebrate pest control has frequently led to the unintentional exposures of non-target animals, especially birds. Several bird species, such as raptors, are suggested to be sensitive to anticoagulant rodenticides, however, the mechanism for this sensitivity has not yet been revealed. In wild rats, two causes are supposed to be possible reasons to explain the mechanism of rodenticide resistance; mutation of vitamin K epoxide reductase (VKOR) gene and acceleration in cytochrome P450-dependent detoxification. In case of wild birds, we reported that some of raptors have very low CYP-dependent warfarin metabolic activity relative to other avian species. In addition, we also showed Ki (inhibitory constant) for VKOR activity after warfarin treatment was 17- to 40-fold lower in ostriches or rats than in chickens. These facts were the first to indicate high warfarin resistance of chickens, and species difference in rodenticide sensitivity among birds.

　On Sakhalin Island (Russia), oil and natural gas exploitation called the Sakhalin Development is underway along the northeastern coastal area, the breeding ground of the endangered Steller’s Sea Eagle (Haliaeetus pelagicus). An ecological study of this species conducted since 2000, has found 300 breeding pairs and 1,000 nests around an extremely shallow lagoon, which communicates with the Sea of Okhotsk. There is a risk that if a pipeline laid in lagoon or coastal wetland breaks, the resulting oil contamination will destroy the ecosystem and the food resources of the eagle. Sakhalin Island also has fragile soils and active faults which undergo repeated freeze-thaw cycles. Pipeline ruptures in these areas could spread oil throughout the adjacent rivers, wetlands and lagoons, and even to the Sea. In February 2006, more than 5,500 petroleum contaminated sea birds were found dead on the Shiretoko Peninsula of Hokkaido. The oil, from an unknown source, may have drifted with the coastal eastern Sakhalin current to affect these birds. Oil contamination causes birds to lose buoyancy and insulation which leads to drowning and/or hypothermia. Many individuals had petroleum in their gastrointestinal tract, often ingested through feather preening. Two dead Steller’s Sea Eagles were found in the same area as the seabirds. The stomachs of these birds contained blackish-brown oil covered seabird feathers and bones. In addition, pathology associated with heavy oil ingestion, such as adrenal gland and thyroid enlargement, were found.

　Histological characterization of brachial gland in slow loris (Nycticebus coucang) is described. Histologically, and ultrastructurally, the brachial gland was similar to apocrine gland. It consists of excretory ducts which open to hair follicle and three distinct terminal portions. Immunohistochemically, the terminal portion was classified into two types. One terminal portion showed the positive to the apocrine-gland marker, but glandular-epithelium marker and eccrine gland marker were negative. Another showed the positive to all the markers. It is concluded that brachial gland in slow loris consists of three distinct terminal portions which has morphological characteristics of apocrine gland. However, these terminal portions were suggested that it were classified into apocrine gland, and the gland which has an immunohistochemical feature of both apocrine and eccrine gland.