Independent evolution of striated muscles in cnidarians and bilaterians

Striated muscles are present in bilaterian animals (for example, vertebrates, insects and annelids) and some non-bilaterian eumetazoans (that is, cnidarians and ctenophores). The considerable ultrastructural similarity of striated muscles between these animal groups is thought to reflect a common evolutionary origin. Here we show that a muscle protein core set, including a type II myosin heavy chain (MyHC) motor protein characteristic of striated muscles in vertebrates, was already present in unicellular organisms before the origin of multicellular animals. Furthermore, 'striated muscle' and 'non-muscle' myhc orthologues are expressed differentially in two sponges, compatible with a functional diversification before the origin of true muscles and the subsequent use of striated muscle MyHC in fast-contracting smooth and striated muscle. Cnidarians and ctenophores possess striated muscle myhc orthologues but lack crucial components of bilaterian striated muscles, such as genes that code for titin and the troponin complex, suggesting the convergent evolution of striated muscles. Consistently, jellyfish orthologues of a shared set of bilaterian Z-disc proteins are not associated with striated muscles, but are instead expressed elsewhere or ubiquitously. The independent evolution of eumetazoan striated muscles through the addition of new proteins to a pre-existing, ancestral contractile apparatus may serve as a model for the evolution of complex animal cell types.     

非均匀光照下人脸眼睛的定位方法

考虑非均匀光照下人脸眼睛的检测问题，提出了一种利用高频信息模板匹配方法从复杂图像中定位人脸眼睛的方法。选取80幅光线较好的人脸图像，对它们做光线规范化，提取Gabor高频特征，构造模板。利用统计模式识别的原理，在眼睛的大致区域进行模板匹配，突出眉毛与眼睛这一整体的大致位置，然后进行二值投影，最终确定人眼的准确位置。大量实验表明，该算法具有很高的精度和很强的鲁棒性。