In karyotype of many organisms, chromosomes form two distinct size groups: macrochromosomes and microchromosomes. During cell divisions, the position of the macro- and microchromosomes is often ordered within metaphase plate. In many reptiles, amphibians, birds, insects of the orthopteran family Tettigoniidae and in some plants, a so called "reptilian" type organization is found, with microchromosomes situated in the center of metaphase plate and with macrochromosomes situated at the periphery. An opposite, "lepidopteran" type is known in butterflies and moths (i.e. in the order Lepidoptera) and is characterized by macrochromosomes situated in the center and by microchromosomes situated at the periphery. The anomalous arrangement found in Lepidoptera was previously explained by holocentric organization of their chromosomes. Here I analyse the structure of meiotic metaphase I plates in ithomiine butterfly, Forbestraolivencia (H. Bates, 1862) (Nymphalidae, Danainae, Ithomiini) which has a clear "reptilian" organization, contrary to previous observations in Lepidoptera. In this species large bivalents (i.e. macrochromosomes) form a regular peripheral circle, whereas the minute bivalents (i.e. microchromosomes) occupy the center of this circle. The reasons and possible mechanisms resulting in two drastically different spatial chromosome organization in butterflies are discussed.

中文翻译：

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蝴蝶（鳞翅目）中期板中的两种高度有序的微染色体和大染色体排列。

在许多生物的核型中，染色体形成两个不同的大小组：大染色体和微染色体。在细胞分裂过程中，大染色体和微染色体的位置通常在中期板上排列有序。在许多爬行动物，两栖动物，鸟类，直翅目科的昆虫和一些植物中，发现了一种所谓的“爬行动物”型组织，其微染色体位于中期板的中心，而大染色体位于外围。在蝴蝶和飞蛾中已知相反的“鳞翅目”类型（即鳞翅目），其特征在于位于中心的大染色体和位于外围的微染色体。鳞翅目中发现的异常排列以前是通过染色体的整体中心组织来解释的。在这里，我分析了依托米因蝴蝶Forbestraolivencia（H. Bates，1862）（Nymphalidae，Danainae，Ithomiini）减数分裂中期I板的结构，该组织具有明显的“爬行类”组织，这与鳞翅目先前的观察相反。在该物种中，大的二价（即大染色体）形成规则的外围圆，而微小的二价（即微染色体）占据该圆的中心。讨论了导致蝴蝶中两个空间染色体显着不同的原因和可能的机制。在该物种中，大的二价（即大染色体）形成规则的外围圆，而微小的二价（即微染色体）占据该圆的中心。讨论了导致蝴蝶中两个空间染色体显着不同的原因和可能的机制。在该物种中，大的二价（即大染色体）形成规则的外围圆，而微小的二价（即微染色体）占据该圆的中心。讨论了导致蝴蝶中两个空间染色体显着不同的原因和可能的机制。