信鸽瓶状囊耳石中磁性元素的电感耦合等离子体质谱分析

Abstract

Objective The macula lagena in birds is located at the apical end of the cochlea and contains many tiny otoliths.The macula lagena is innervated and has neural projections to the brainstem, but its physiological function is still unclear. It remains disputable that it is because otoliths in the lagena are rich in elements Fe and Zn that birds can obtain geomagnetic information for homing. To clarify this issue, we carried out a study to determine whether or not otoliths in the lagena of homing pigeons are richer in magnetic elements than those in the saccule and the utricle. Methods The contents of ferromagnetic elements (Fe, Co, Ni) and other metal elements in lagenal otoliths of adult homing pigeons were precisely analyzed with inductively coupled plasma mass spectrometry (ICP-MS) of high sensitivity, and then they were compared with those in saccular and utricular otoliths (all the contents were normalized to Ca). Results In adult homing pigeons, the contents of ferromagnetic elements (Fe, Co, Ni) in lagenal otoliths were less than 0.7% (normalized to Ca element) and were the same order in magnitude as those in saccular and utricular otoliths. The content of Fe in lagenal otoliths was not significantly different from that in utricular otoliths and was even lower than that in saccular otoliths. The content of Co in lagenal otoliths was lower than that in saccular otoliths and higher than that in utricular otoliths. The content of Ni in lagenal otoliths was not significantly different from that in saccular otoliths and was higher than that in utricular otoliths. The contents of other metal elements Na, Mg, K, Al, Mn and Pb in lagenal otoliths were not significantly different from those in utricular and saccular otoliths. The contents of metal elements Zn, Ba and Cu in lagenal otoliths were lower than those in saccular otoliths. ConclusionThe contents of magnetic elements in lagenal otoliths of homing pigeons are not much higher than those in utricular and saccular otoliths, which does not support the hypothesis that birds depend on high contents of Fe and Zn in lagenal otoliths for sensation of geomagnetic information. Similarities in morphology, element ingredient and element content between lagenal otoliths and utricular otoliths suggest that the two types of otolithic organs may play similar roles in sensing gravitational and acceleration signals.

No evidence for a magnetite-based magnetoreceptor in the lagena of pigeons

“…We acknowledge that our TEM screen may have failed to identify single superparamagnetic magnetite crystals smaller than 10 nm in size; however, such crystals could not serve as a torque-based magnetoreceptor that would provide information on the polarity of the magnetic fi eld [8]. Moreover, our fi ndings are consistent with that of Zhao et al [9], who performed mass-spectrometric analysis on the lagenar otoconia of pigeons and show a near absence of iron. How can these fi ndings be reconciled with the data that magnetic stimuli cause neuronal activation in the vestibular nuclei of pigeons?…”

Development of Spontaneous Activity and Response Properties of Primary Lagenar Neurons in the Chick

“…In a similar way, a recent finding about the similar contents of magnetic elements in lagenar otoliths of homing pigeons and those in utricular and saccular otoliths shows the similarity between the lagena and the other vestibular end organs in birds (Zhao et al 2009). …”

Cerebellar Projections of the Lagena (the Third Inner Ear Otolith Endorgan) in the Pigeon

“…According to the recently obtained data, the lagena in birds does not differ significantly in the content of ferromagnetics (Fe, Co, and Ni) in the sacculus and utriculus [33]. A great majority of lagenar otoconia are similar in their shape (regular cylindrical) to saccular and utricular ones [34]; this fact does not agree with the supposition of specificity of function of the apparatus of lagenar otoconia.…”