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鳝鱼,又名黄鳝,是我国南方各省区极为常见的鱼类。它不但营养丰富,食用价值很高,而且还可以药用,治疗颜面神经麻痹及中耳炎。但黄鳝的性别决定很特殊,在其个体发育中具有性反转现象。经实验解剖发现,黄鳝在体长200毫米以下时全为雌性,而体长530毫米以上的黄鳝则全为雄性。也就是说,黄鳝小时候是雌性的,长大以后就变成雄性的,下面就黄鳝的性反转现象作些分析,供同行参考。 首先,从性染色体来看,一般生物的性别是由性染色体决定的,如 XY型和ZW型性别决定。但长期以来,鱼类的性别决定和性染色体问题一直是悬而未决。在2万多种鱼类中,目前研究查明仅有30多种鱼类有异形的性染色体。一般的看法,鱼类性别的决定机制仍处于很原始状态,性染色体和常染色体在形态上很难区别。从目前对黄鳝的染色体组型分析及显带来看,其染色体数目为2n=24,染色体臂数为N·F=24,所有染色体为端着丝点染色体,没有具次缢痕和随体的染色体,也没有发现异形染色体。这里并不排除黄缮有性染色体的存在,因为黄鳝在鱼类进化上是一个已经特化的种类。但从黄鳝这种自然状态性反转来看,黄鳝是没有性染色体的。假设黄鳝属于XY型性别决定,有XY性染色体存在的话,那么具有XX和XY型性染色体的个体在其自然发育长为成体时应分别为雌性和雄性,这
Eel, also known as eel, is a very common fish in southern provinces of our country. It is not only nutritious, high food value, but also can be medicated, facial nerve paralysis and treatment of otitis media. However, the eel’s sex decision is very special, in its individual development has the phenomenon of sexual inversion. The experimental dissection found that the eel in the body length of 200 mm below the whole female, while the length of 530 mm above the eel are all male. In other words, eel as a child was female, grew up into a male, following the eel of the phenomenon of sexual inversion for some analysis for peer reference. First of all, from the sex chromosomes, the general biological sex is determined by the sex chromosomes, such as XY and ZW sex decisions. However, the sex determination and sex chromosomes of fish have long been unresolved. Of more than 20,000 species of fish, the current study identified only 30 kinds of fish have abnormal sex chromosomes. As a general rule, the mechanism for determining the sex of fish is still very primitive, and sex chromosomes and autosomes are difficult to distinguish morphologically. From the current eel genome analysis and banding, the number of chromosomes is 2n = 24, the number of chromosome arms is N · F = 24, all chromosomes are telocentric chromosomes, No chromosomal abnormalities were found. This does not rule out the presence of sex chromosomes in Huangshan because the eel is a specialized species in fish evolution. However, eel this natural state of reverse sex, eel is no sex chromosomes. Assuming that the eel belongs to the XY genotype, there are XY sex chromosomes, then individuals with XX and XY sex chromosomes should be female and male, respectively, when their natural development is adult