The Visual System and Paleoecology of the Silurian Ostracod Primitiopsis planifrons
The Visual System and Paleoecology of the Silurian Ostracod Primitiopsis planifrons
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DOI：
10.1666/08-124.1
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发表时间：
2009-05
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影响因子：
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通讯作者：
G. Tanaka;D. Siveter;A. Parker
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文献类型：
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作者：
G. Tanaka;D. Siveter;A. Parker
摘要本文报道了一种古生代介形类的眼睛和视觉系统的首次详细重建，即二型性的Primitiopsid(Palaeocopa)Primitiopsis Planifrons Jones，1887。从角质层晶状体的形态和它在瓣膜上的位置的证据表明，平纹夜蛾有一只无节体眼，这是甲壳类最常见的光学系统。眼睛的特征，如每个瓣膜上分离的角质层晶状体，晶状体及其直径的强钙化性质，与最近一些足足介形类的特征一致，其中存在分裂类型的无节幼体眼。原始足目动物重建的角质层晶状体的光线追踪显示出很强的球面像差和很长的焦距(与足足类动物的眼睛一样)，这意味着晶状体下方存在球面镜(绒毛膜)。对瓣膜厚度的个体发育变化的研究有助于推测平腹藻是内底栖动物。它的角质层晶状体相对于现存的足足介形虫的大小，以及这些新近出现的形态出现的水深，表明P.Planifrons可能生活在相对较浅、光照较好的环境中，例如深潮下带。这些解释与根据地质证据推测的古环境条件是一致的。因此，对眼睛的性质和相对大小的分析给出了一项独立的测试，以帮助识别早已灭绝的介形类的古环境参数。
Abstract Here we report the first detailed reconstruction of the eye and visual system of a Paleozoic ostracod, namely the dimorphic primitiopsid (Palaeocopa) Primitiopsis planifrons Jones, 1887. Evidence from the cuticular lens morphology and its position on the valve suggests that P. planifrons had a naupliar eye, which is the most common optical system in crustaceans. The characters of the eye, such as the separated cuticular lens on each valve and the strongly calcified nature of the lens and its diameter, are concordant with that of some Recent podocopid ostracods in which a divided type of naupliar eye is present. Ray tracing of the reconstructed cuticular lens of the primitiopsid species demonstrates strong spherical aberration and a very long focal length (as in the eye of podocopids), which implies the presence of a spherical mirror (tapetum) below the lens. Study of the ontogenetic change of the valve thickness aids the suggestion that P. planifrons was nektobenthic. The size of its cuticular lens in relation to that of living podocopid ostracods, and the water depth at which these Recent forms occur, indicates that P. planifrons may have lived in a relatively shallow, well lit environment such as the deep subtidal zone. These interpretations are consistent with supposed paleoenvironmental conditions derived from geological evidence. Thus, analysis of the nature and relative size of the eye gives an independent test to help identify paleoenvironmental parameters of long extinct ostracods.