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Passerine migrants require light from the blue-green part of the spectrum for magnetic compass orientation; under yellow light, they are disoriented. European robins tested under a combination of yellow light and blue or green light showed a change in behavior, no longer preferring their seasonally appropriate migratory direction: in spring as well as in autumn, they preferred southerly headings under blue-and-yellow and northerly headings under green-and-yellow light. This clearly shows that yellow light is not neutral and suggests the involvement of at least two types of receptors in obtaining magnetic compass information, with the specific interaction of these receptors being rather complex. 相似文献
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One of the most useful diagnostic therian features is the division of the lateral surface of the scapula into two fossae separated by a scapular spine. A new model to describe this evolutionary innovation based on ontogenetic data is provided, consistent with information provided by recent fossil discoveries. The development of the scapula in three didelphid and one dasyurid marsupials using histological sections was studied. Only the ventral, acromial portion of the scapular spine, which originates from the anterior margin of the scapular blade, is preformed in cartilage. The major dorsal portion is formed at a later stage by appositional bone, which expands from the perichondral ossification of the scapula into an intermuscular aponeurosis between the supra-and infraspinatus muscles. This intermuscular aponeurosis inserts more or less in the middle of the lateral surface of the developing scapula. Thus, the floor of the supraspinous fossa is already present at the beginning of scapular development, simultaneous with the infraspinous fossa. The portion of the scapular spine that is situated dorsal to the acromial process is hypothesized to be a neomorphic structure of therians. The dorsal portion of the scapular spine evolved as additional attachment for powerful supraspinatus and infraspinatus muscles meeting near the middle of the lateral scapula. 相似文献
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