Rhamphotheca as a useful indicator of mercury in seabirds

New insights on the use of bill sheath as a biomonitoring tool for mercury in two kingfisher species: A comparison with different tissues

“…rhamphotheca and claws), which have also been shown to be adequate indicators of THg body burden in birds. Moreover, our results support previous outcomes for the yellow-legged gull Larus michahellis (de Medeiros Costa et al, 2021) and endorse that rhamphotheca is a powerful approach to assessing Hg changes in bird colonies, as well as a proxy tor accurately measurement of Hg body burdens. Indeed, according to our results, feathers may be more useful for effects monitoring, or spatial patterns, where rhamphotheca may be more useful for temporal trends.…”

“…The use of the rhamphotheca as an indicator of environmental Hg has been recently suggested (de Medeiros Costa et al, 2021) because it is an organ basically composed of β-keratin (Seki et al, 2010), with compacted cells (Handel et al, 2010), presenting amino acid sequences homologous to those found in feathers (Frenkel and Gillespie, 1976;Wickham, 2009;Wickham, 2009), little interspecific variation (Frenkel and Gillespie, 1976;Wickham, 2009). Rhamphotheca is about 46% more rigid than feathers, which indicates a higher proportion of keratin (Barbosa et al, 2016).…”

“…Despite the large number of studies using feathers to assess environmental Hg levels, a scientific debate still exists on the suitable indicator for monitoring Hg in birds (Peterson et al, 2019). Similar to feathers and claws, the bill sheath, known as rhamphotheca, is composed of keratin, has continuous growth, receives circulating blood (Tattersall et al, 2017), and it has been proposed as an indicator for monitoring Hg in gulls (de Medeiros Costa et al, 2021), however its usefulness has not yet been demonstrated in other bird species.…”

Drivers of biomagnification of Hg, As and Se in aquatic food webs: A review

“…The bioaccumulation of Hg in seabirds and waterbirds species is also worrisome, because it affects the flight capacity and the health status of birds with different feeding habits (Ullah et al, 2014;Whitney and Cristol, 2017). This effect occurs because Hg has a high affinity to keratin in feathers and ramphoteca, rich in sulphur-containing amino acids (L-cysteine) (de Medeiros Costa et al, 2021). In this sense, blood Hg levels are influenced by feather growth and moulting (Condon and Cristol, 2009), therefore, depuration occurs more rapidly in molting birds and reduction of Hg concentrations can be up to 90% of the concentrations in the blood during the molting process (Whitney and Cristol, 2017).…”