Metallothionein levels in willow ptarmigan (Lagopus lagopus) populations with different natural loads of cadmium

Abstract

The tissues of willow ptarmigan in some Norwegian mountain areas contain elevated concentrations of cadmium (Cd). It is not known whether such high Cd levels would have negative impacts in otherwise healthy populations of this species. The aim of the current study was to clarify relationships between hepatic and renal metallothionein (MT) and Cd concentrations in willow ptarmigan to assess effects from this metal. The study reported here was undertaken on willow ptarmigan from the Kongsvoll area, with a naturally high Cd load, and the Essand area, with a naturally low Cd load. Cd values in liver and kidney in willow ptarmigan from Kongsvoll were significantly higher than in willow ptarmigan from Essand. The MT content in both tissues was also highest in willow ptarmigan from Kongsvoll. The MT concentration in kidney was twice that in liver for ptarmigan from both areas and at all times of the year. The MT level in both liver and kidney varied greatly throughout the season, with the highest content in spring (May). The variation was greatest in liver. The total material showed a significant linear relationship between Cd and MT levels in both liver and kidney, but a breakdown of the material into seasons and areas gave a varying degree of significance. MT in willow ptarmigan may be an important mechanism for detoxifying Cd, and populations exposed to high load may "respond" to the loads by increasing MT synthesis in tissues such as liver and kidney. There is no evidence that willow ptarmigan from areas with high natural Cd loads have reached a limit for MT synthesis in either liver or kidney.

Behavioural effects of cadmium (Cd) in free-living willow ptarmigan (Lagopus lagopus)

“…For mice, the halftime has been documented to be about 100-300 days (Friberg et al 1971). In accordance with previous studies in various bird species (e.g., Scheuhammer 1987;Pedersen and Hylland 2007), a significant correlation between the concentration of Cd and MT in kidney was found. Parental behaviour shown by willow ptarmigan hens is important for the survival of the chicks (Pedersen and Steen 1985).…”

“…However, in spite of an apparently well-developed ability to produce MT (Pedersen and Hylland 2007), reduced parental behaviour and increased chick mortality was reported after the experimentally increased exposure to Cd in willow ptarmigan from Kongsvoll (Pedersen and Saether 1999). The observed behavioural effect may be because willow ptarmigan at Kongsvoll were not able to produce sufficient MT to detoxify the additional load of Cd.…”

“…If this is the case, their inability to produce sufficient amounts of MT to counteract an additional load of Cd may be because Cd does not represent a strong selection pressure. On the other hand, their natural high baseline levels of MT (Pedersen and Hylland 2007) may reflect an evolutionary adaptation to the relatively high Cd concentrations of geological origin at Kongsvoll.…”

“…Indeed, it has been shown that MT levels were higher in willow ptarmigan from Kongsvoll as compared to another location in Norway where geological Cd levels are lower (Pedersen and Hylland 2007). Thus, in willow ptarmigan, MT may be an important mechanism for detoxifying Cd, and a population which experience high loads, for instance through a high intake of willow, may respond by increasing their MT production.…”

“…However, the reduction in parental behaviour and chick survival was not very strong. This might be because that particular study was undertaken in a location where willow ptarmigan have relatively high levels of Cd due to the geological characteristics of the area (Relling 1993;Pedersen and Hylland 2007).…”