{"title":"三叶虫(pseudoagnostina, Trilobita?)的复杂表皮结构","authors":"E. B. Naimark, S. Yu. Chaika","doi":"10.1134/s0031030123070080","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The cuticle of <i>Pseudagnostus</i> ex gr. <i>cyclopyge</i>, a member of Agnostina, which is currently conditionally considered as an arthropod stem lineage, was studied using SEM. It has been believed so far that the agnostoid cuticle is simple and single-layered, differing in its primitive structure from other arthropods, both modern and extinct. However, our results showed that at least in this species, the cuticle has a very complex structure. Their carapace consisted of three layers, and each layer was characterized by its own features. The outer layer, which was a combination of a thin upper prismatic unit and a thick principal unit composed of relatively loosely packed lamellae, overlies the transitional layer. The transitional layer consists of stacks of thin lamellae, directed differently in each stack. On the thin inner layer there were numerous pits with a central element (peg). The peg pits create a specific profile of the inner layer, although the functions of these peg pits are not clear. The inner layer is underlain by a basal matrix of rhomboid fibrillar mesh possibly of chitin-protein nature. Specific cuticular sensilla were found both on the outer and inner layers. On the glabellar culmination there is a V-shaped groove with two rows of digitiform sensilla in the V-branches; campaniform sensilla were located along the symmetry axis between the branches. This sensory field apparently performed a mechanosensory function responding to currents outside an enrolled animal. Given the complexity of the integument of this species, further comparison with other agnostoid species, as well as with the cuticle of other arthropods, is needed. Such a comparison would be promising for understanding the phylogenetic position of Agnostina, as well as the evolution of the arthropod exoskeleton.</p>","PeriodicalId":19816,"journal":{"name":"Paleontological Journal","volume":null,"pages":null},"PeriodicalIF":0.7000,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"The Complex Structure of the Cuticle of Pseudagnostus (Agnostina, Trilobita?)\",\"authors\":\"E. B. Naimark, S. Yu. Chaika\",\"doi\":\"10.1134/s0031030123070080\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<h3 data-test=\\\"abstract-sub-heading\\\">Abstract</h3><p>The cuticle of <i>Pseudagnostus</i> ex gr. <i>cyclopyge</i>, a member of Agnostina, which is currently conditionally considered as an arthropod stem lineage, was studied using SEM. It has been believed so far that the agnostoid cuticle is simple and single-layered, differing in its primitive structure from other arthropods, both modern and extinct. However, our results showed that at least in this species, the cuticle has a very complex structure. Their carapace consisted of three layers, and each layer was characterized by its own features. The outer layer, which was a combination of a thin upper prismatic unit and a thick principal unit composed of relatively loosely packed lamellae, overlies the transitional layer. The transitional layer consists of stacks of thin lamellae, directed differently in each stack. On the thin inner layer there were numerous pits with a central element (peg). The peg pits create a specific profile of the inner layer, although the functions of these peg pits are not clear. The inner layer is underlain by a basal matrix of rhomboid fibrillar mesh possibly of chitin-protein nature. Specific cuticular sensilla were found both on the outer and inner layers. On the glabellar culmination there is a V-shaped groove with two rows of digitiform sensilla in the V-branches; campaniform sensilla were located along the symmetry axis between the branches. This sensory field apparently performed a mechanosensory function responding to currents outside an enrolled animal. Given the complexity of the integument of this species, further comparison with other agnostoid species, as well as with the cuticle of other arthropods, is needed. Such a comparison would be promising for understanding the phylogenetic position of Agnostina, as well as the evolution of the arthropod exoskeleton.</p>\",\"PeriodicalId\":19816,\"journal\":{\"name\":\"Paleontological Journal\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.7000,\"publicationDate\":\"2023-11-30\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Paleontological Journal\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1134/s0031030123070080\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"PALEONTOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Paleontological Journal","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1134/s0031030123070080","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"PALEONTOLOGY","Score":null,"Total":0}
引用次数: 0
摘要
摘要利用扫描电镜对目前有条件被认为是节肢动物茎系的假agnosteus ex gr. cyclopyge的角质层进行了研究。迄今为止,人们一直认为这种无知者角质层很简单,是单层的,其原始结构与其他节肢动物不同,无论是现代的还是灭绝的。然而,我们的结果表明,至少在这个物种中,角质层具有非常复杂的结构。它们的甲壳由三层组成,每一层都有自己的特征。外层覆盖在过渡层之上,由较薄的上层棱柱单元和由相对松散的片层组成的较厚的主单元组成。过渡层由一层层的薄片组成,每一层的方向不同。在薄的内层上有许多带有中心元件(钉)的凹坑。尽管这些钉坑的功能尚不清楚,但钉坑创造了内层的特定轮廓。内层为菱形纤维网状基底基质,可能为几丁质蛋白性质。外、内层均有特异的表皮感受器。在蝶弓顶部有一个v形沟槽,v形枝上有两排数字化感受器;钟形感受器沿树枝之间的对称轴分布。这个感觉场显然执行一种机械感觉功能,对实验动物外部的电流做出反应。考虑到该物种被皮的复杂性,需要与其他未知物种以及其他节肢动物的角质层进行进一步的比较。这样的比较将有助于了解Agnostina的系统发育位置,以及节肢动物外骨骼的进化。
The Complex Structure of the Cuticle of Pseudagnostus (Agnostina, Trilobita?)
Abstract
The cuticle of Pseudagnostus ex gr. cyclopyge, a member of Agnostina, which is currently conditionally considered as an arthropod stem lineage, was studied using SEM. It has been believed so far that the agnostoid cuticle is simple and single-layered, differing in its primitive structure from other arthropods, both modern and extinct. However, our results showed that at least in this species, the cuticle has a very complex structure. Their carapace consisted of three layers, and each layer was characterized by its own features. The outer layer, which was a combination of a thin upper prismatic unit and a thick principal unit composed of relatively loosely packed lamellae, overlies the transitional layer. The transitional layer consists of stacks of thin lamellae, directed differently in each stack. On the thin inner layer there were numerous pits with a central element (peg). The peg pits create a specific profile of the inner layer, although the functions of these peg pits are not clear. The inner layer is underlain by a basal matrix of rhomboid fibrillar mesh possibly of chitin-protein nature. Specific cuticular sensilla were found both on the outer and inner layers. On the glabellar culmination there is a V-shaped groove with two rows of digitiform sensilla in the V-branches; campaniform sensilla were located along the symmetry axis between the branches. This sensory field apparently performed a mechanosensory function responding to currents outside an enrolled animal. Given the complexity of the integument of this species, further comparison with other agnostoid species, as well as with the cuticle of other arthropods, is needed. Such a comparison would be promising for understanding the phylogenetic position of Agnostina, as well as the evolution of the arthropod exoskeleton.
期刊介绍:
Paleontological Journal (Paleontologicheskii zhurnal) is the principal Russian periodical in paleontology. The journal publishes original work on the anatomy, morphology, and taxonomy of fossil organisms, as well as their distribution, ecology, and origin. It also publishes studies on the evolution of organisms, ecosystems, and the biosphere and provides invaluable information on global biostratigraphy with an emphasis on Eastern Europe and Asia.