Spermatozoal ultrastructure of the taxon Enchytraeus (Annelida, Oligochaeta) and its significance for species discrimination and identification1,2
Spermatozoal ultrastructure of the taxon Enchytraeus (Annelida, Oligochaeta) and its significance for species discrimination and identification1,2
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类群 Enchytraeus（环节动物、寡毛类）的精子超微结构及其物种判别和鉴定的意义1,2
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发表时间：
2009
期刊：
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通讯作者：
K. Middendorf
中科院分区：
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作者：
W. Westheide;G. Purschke;K. Middendorf
寡毛纲Enchytraeus属的物种在形态上相当相似;它们在传统的光学显微镜方法上很难区分，甚至无法分开。对来自19个不同来源的种群和某些未知种属的个体的成熟精子的超微结构进行了研究。它们的形态测量和质量数据被用作形态分类特征。除了E. albidusc>，研究的材料来自遗传单态实验室近交系。线状精子的结构通常与该科已知的精子类型一致。使用的数字字符为1。顶体长度，2.螺旋状核的长度，3.核法兰的螺旋形尖顶的数量，4.凸缘近端和远端螺旋的周期性，5.凸缘与髓核纵轴的夹角，6.中间段的长度，7.线粒体螺旋状螺旋的数量，和8。鞭毛的长度。除了核的形状，顶体的复杂结构提供了进一步的具体的质的差异，如，初级顶体囊泡的长度比整个顶体，亚远端电子致密材料的延伸，和初级顶体囊泡下面的特定结构的存在或不存在。
八个人口显示出高度显着的差异，彼此之间的基础上，从其余人口的形态计量数据。此外，这些群体-在常规方法上可识别为不同的物种-也可以通过其精子的质量差异来区分。其他10个种群的精子似乎是高度相似的，由于其核的长度。然而，核螺旋的数量，顶体的长度，凸缘螺旋的周期性，特别是顶体的结构细节，将这10个群体分成两个显着不同的组，一个有6个物种，另一个有4个。这四个组，也被发现在平行，独立进行的非形态学调查，被认为是属于一个物种。某些形态学数据将六个组分为两组，每组三个，这也得到了非形态学方法和杂交实验的支持-两组都是不同的物种。
统计学比较通常表明，一个人的精子的形态测量数据没有或只有轻微的变化。遗传单态实验室培养物个体之间的变异性较高，但在任何情况下都不会妨碍种属鉴定。在E. albidus田间种群：在单酶模式上不同的个体的精子在它们的形态测定数据上显著地偏离，并且仅基于这些形态测定数据，它们与某些其它物种的精子是不可分离的。然而，质量特征不受影响，并且可以根据顶体结构容易地区分物种。
本例的精子比较表明的可能性和重要性，超微结构分析作为一种先进的形态学方法解决分类学问题的物种水平。
Species of the oligochaete genus Enchytraeus are morphologically rather similar; they are difficult to distinguish or even inseparable on conventional light microscopic methods. In individuals from 19 populations of different origin and in some cases unknown species identity the ultra-structure of mature spermatozoa was investigated. Their morphometric and qualitative data were used as morphological taxonomic characters. With the exception of a genetically polymorphic field population of E. albidussc>, the material investigated came from genetically monomorphic laboratory inbred strains. The structure of the thread-like spermatozoa generally conforms with the sperm type known for the family. Numerical characters used were 1. length of the acrosome, 2. length of the corkscrew-like nucleus, 3. number of helical spires of the nuclear flange, 4. periodicity of the flange spires proximally and distally, 5. angle of the flange to the longitudinal axis of the nucleus, 6. length of the midpiece, 7. number of mitochondrial helical spires, and 8. length of the flagellum. Besides the shape of the nucleus, the complex structure of the acrosome provides further specific qualitative differences such as, length ratio of primary acrosome vesicle to the entire acrosome, extension of a subdistal electron-dense material, and absence or presence of specific structures underneath the primary acrosome vesicle.
Eight populations show highly significant differences from each other and from the remaining populations on the basis of morpnometric data alone. In addition, these populations - recognizable as different species on conventional methods - can also be discriminated by qualitative differences of their spermatozoa. The spermatozoa of 10 other populations appear to be highly similar due to the length of their nuclei. Number of nuclear spires, length of acrosome, flange spire periodicity and especially structural details of the acrosome, however, separate these 10 populations into two significantly different groups, one with six species and the other with four. The group of four, which has also been found in parallel, independently conducted non-morphological investigations, are considered to belong to one species. Certain morphological data divide the group of six into two groups of three, which is also supported by non-morphological methods and crossbreeding experiments - both groups are distinct species.
Statistical comparisons generally show no or only slight variability of morphometric data for sperm of one individual. The variability between individuals of the genetically monomorphic laboratory cultures is higher but in no case does it prevent species identification. The greatest intraspecific variation has been observed in the E. albidus field population: spermatozoa of individuals differing in the pattern of single enzymes deviate significantly in their morphometric data, and on the basis of these morphometric data alone they are inseparable from spermatozoa of certain other species. However, qualitative characters are not affected and species can easily be discriminated on the basis of acrosomal structures.
The present example of a comparison of spermatozoa demonstrates the possibilities and importance of ultrastructural analysis as an advanced morphological method for solving taxonomical problems at the species level.