Ontogeny and evolution of electric organs in gymnotiform fish
Ontogeny and evolution of electric organs in gymnotiform fish
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DOI：
10.1016/j.jphysparis.2008.10.008
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发表时间：
2008-07-01
影响因子：
--
通讯作者：
Schwassmann, H. O.
中科院分区：
文献类型：
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作者：
Kirschbaum, F.;Schwassmann, H. O.
为了进一步了解新热带裸形鱼类电器官的进化，我们研究了八种鱼类电器官的个体发育。在 Eigenmannia virescens、Sternopygus macrurus、a 和 Apteronotus leptorhynchus 中，最早的电细胞位于下轴肌的肌纤维之间（A 型电细胞）。我们提出这些 A 型电细胞代表了拟形状态的论点。在 S. macrurus 中，除了下轴肌中的电细胞外，还在上轴肌中发现了额外的电细胞。在细喙猴中，除了早期的肌源性器官外，神经源性器官在个体发育后期还在下轴肌的内侧部分发育。在 E. virescens 中，下轴肌中的早期电细胞将在个体发育后期退化，并且该器官将在功能上被位于尾附属器和下轴肌下方的电细胞取代。在 Electrophorus electricus 中，两种 Gymnotus 物种：Rhamphichthys sp. 和 Brachyhypopomus pinnicaudatus，在下轴肌下方发现了第一个电细胞（B 型电细胞）；它们被认为是更衍生的阶段。在 R. sp. 和 B. pinnicaudatus 中，B 型电细胞直接发育成成体器官。在两个 Gymnotus ssp 中。在下轴肌的肌纤维之间的器官内侧部分也发现了电细胞。在电虫中，观察到发芽区与腹侧肌节分离。该区域不断产生电细胞，因此，电器官与肌肉的相对比例大大增加。在 45 毫米长的 E. electricus 中，观察到低压定向脉冲和高压脉冲序列（冲击）的分离。亨特器官首次出现于 140 毫米的电虫标本中。所有研究物种的第一次放电均为头部阳性，但 R. sp. 除外，它产生三相放电，但其主要成分为头部阳性。提出的论点表明，在 E. virescens、S. macrurus 和 A. leptorhynchus 中发现的 A 型电细胞代表了拟形条件。根据有关形成、细胞学外观和解剖位置的证据以及早期电记录，我们假设在裸形动物的进化过程中，波型物种首先进化，然后在第二步中进化出脉冲型物种。然而，这种观点仅得到一些系统发育假设的证实。 (C) 2008 Elsevier Ltd. 保留所有权利。
In order to further our understanding of the evolution of electric organs in the Neotropical gymnotiform fish, we Studied the ontogeny of the electric organs in eight species. In Eigenmannia virescens, Sternopygus macrurus, a and Apteronotus leptorhynchus the earliest electrocytes are located between muscle fibres of the hypaxial muscle (Type A electrocytes). We present arguments that these Type A electrocytes represent the plesiomorphic condition. In S. macrurus, in addition to the electrocytes in the hypaxial muscle, additional electrocytes were found in the epaxial muscle. In A. leptorhynchus a neurogenic organ develops later during ontogeny in the medial part of the hypaxial muscle in addition to the early myogenic organ. In E. virescens the early electrocytes in hypaxial muscle will degenerate later during ontogeny, and this organ will be replaced functionally by electrocytes located in the caudal appendage and below the hypaxial muscle. In Electrophorus electricus, two Gymnotus species, Rhamphichthys sp., and Brachyhypopomus pinnicaudatus the first electrocytes were found below the hypaxial muscle (Type B electrocytes); they are assumed to be the more derived stage. In R. sp., and B. pinnicaudatus the electrocytes of Type B developed directly into the adult organ. In the two Gymnotus ssp. electrocytes were also found in the medial part of the organ in-between muscle fibres of the hypaxial muscle. In E. electricus a germinative zone was observed to separate from the ventral myotome. This zone is generating electrocytes Continuously SO that, as a consequence, the relative proportion of electric organ to muscle increases greatly. In 45 mm long E. electricus a separation of low voltage orientation pulses and high voltage trains Of Pulses (shocks) was observed. A first appearance of Hunter's organ was found in 140 mm specimens of E. electricus. The first discharges of all species studied were head-positive, with the exception of R. sp., which produced a triphasic discharge, its main component, however, being head-positive. The arguments presented indicate that the Type A electrocytes found in E. virescens, S. macrurus, and A. leptorhynchus would represent the plesiomorphic condition. On the basis of the evidence regarding the formation, cytological appearance, and anatomical location, as well as the early electrical recordings, we Would hypothesise that during the evolution of gymnotiforms wave type species evolved first, and in a second step pulse type species followed. This view, however, is corroborated by only some phylogenetic hypotheses. (C) 2008 Elsevier Ltd. All rights reserved.