| 高肌虫的个体发育及性双形特征 |
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| 引用本文： | 舒德干.高肌虫的个体发育及性双形特征[J].现代地质,1988,2(4):401. |
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| 作者姓名： | 舒德干 |
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| 摘 要： | 行蜕壳式增长的节肢动物个体发育及性双形特征的研究必须建立在其化石种群结构的恢复之上。简单的数理统计是揭示其种群结构特征的钥匙:鉴别是否属正常化石种群,确定蜕壳期数,解释早期幼壳高死亡率与其化石低保存牢的统一。高肌虫个体发育常表现为六至七期明显的蜕壳阶段,蜕壳期间壳体增长率常在性成熟期有显著的减小趋势。物种的正确鉴定及性双形特征的辨识也只有通过个体发育研究才能得到合理的解决;物种在个体发育过程中表现出来的性伏变化,为研究谱系的演化趋向提供重要依据。这种数理统计方法无疑对三叶虫、介形虫等其他节肢动物的个体发育及性双形研究也完全适用。
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| 关 键 词： | 高肌虫 个体发育 性双形 化石种群 数理统计分析 |
ONTOGENY AND DIMORPHISM OF BRADORIIDA |
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| Shu Began.ONTOGENY AND DIMORPHISM OF BRADORIIDA[J].Geoscience——Journal of Graduate School,China University of Geosciences,1988,2(4):401. |
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| Authors: | Shu Began |
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| Institution: | China university of Geosciences |
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| Abstract: | The study of ontogeny and dimorphism of arthropods which develop their carapaces by moulting should be based on the establishment of fossil population structures. Four factors are required to establish the population structure of a
species----all individuals should be: (1) similar to each other morphologically or
show a gradual modification in morphology from smaller individuals to larger ones. (2) autochthonous. (3) contemporaneous; (4) show no sorting. Among a natural population all the individuals of same age usually show normal distribution in a size-frequency histogram. Like survivorship curve of other oceanic invertebrates, the population structure of moulting organisms indicates that the carapace number of each instar is always greatly larger than that of the successive one. The fossil population structure is usually different from that of living organisms, because after the death of animals the residual carapaces were subjected to selective destruction from various agents, resulting in disappearance of most of smaller carapaces. As a result, the number of the carapaces of median size is much larger than that of the earlier instars and also the mature carapaces comprise only a very small part of the whole fossil population both theoretically and practically. As to these fossil populations having a great number of individuals, the mathematical statistics is the key to study the ontogeny and dimorphism.
The fossil population of Dabashanella hemicyclica containing many bothjuvenile and mature carapaces as well as some eggs are well-preserved. Its structural characteristics are typically as follows: 1. There is no allometric growth, i.e. height and length increase proportionally. 2. Among the seven instars, the third, fourth and fifth instars cover most of individuals of the whole population. 3. The growth rates during the earlier moults almost do not change at all. However, they slow down during the mature period. A kind of dimorphism can be seen in the last stages of life circle of Kunmingelloides bulbosus, which is represented by great difference in ratio of carapace height to length. The gradual modification in characters shown in the ontogeny of Zepaera pri?mitiva is of great significance for the explanation of evolutionary trends in a lineage. |
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| Keywords: | : Bradoriida ontogeny dimorphism fossil population mathema-tical statistics |
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