Hammel Jörg U, Nickel Michael
Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Erbertstr. 1, 07743, Jena, Germany.
PLoS One. 2014 Nov 19;9(11):e113153. doi: 10.1371/journal.pone.0113153. eCollection 2014.
Demosponges possess a leucon-type canal system which is characterized by a highly complex network of canal segments and choanocyte chambers. As sponges are sessile filter feeders, their aquiferous system plays an essential role in various fundamental physiological processes. Due to the morphological and architectural complexity of the canal system and the strong interdependence between flow conditions and anatomy, our understanding of fluid dynamics throughout leuconoid systems is patchy. This paper provides comprehensive morphometric data on the general architecture of the canal system, flow measurements and detailed cellular anatomical information to help fill in the gaps. We focus on the functional cellular anatomy of the aquiferous system and discuss all relevant cell types in the context of hydrodynamic and evolutionary constraints. Our analysis is based on the canal system of the tropical demosponge Tethya wilhelma, which we studied using scanning electron microscopy. We found a hitherto undescribed cell type, the reticuloapopylocyte, which is involved in flow regulation in the choanocyte chambers. It has a highly fenestrated, grid-like morphology and covers the apopylar opening. The minute opening of the reticuloapopylocyte occurs in an opened, intermediate and closed state. These states permit a gradual regulation of the total apopylar opening area. In this paper the three states are included in a theoretical study into flow conditions which aims to draw a link between functional cellular anatomy, the hydrodynamic situation and the regular body contractions seen in T. wilhelma. This provides a basis for new hypotheses regarding the function of bypass elements and the role of hydrostatic pressure in body contractions. Our study provides insights into the local and global flow conditions in the sponge canal system and thus enhances current understanding of related physiological processes.
寻常海绵纲动物具有一种白枝型管道系统，其特点是由高度复杂的管道段和领细胞室网络构成。由于海绵是固着滤食性动物，它们的输水系统在各种基本生理过程中起着至关重要的作用。由于管道系统在形态和结构上的复杂性以及流动条件与解剖结构之间的强烈相互依存关系，我们对整个白枝型系统内流体动力学的理解并不完整。本文提供了关于管道系统总体结构的全面形态测量数据、流量测量结果以及详细的细胞解剖学信息，以帮助填补这些空白。我们专注于输水系统的功能性细胞解剖学，并在流体动力学和进化限制的背景下讨论所有相关细胞类型。我们的分析基于热带寻常海绵纲动物威廉粗皮海绵的管道系统，我们使用扫描电子显微镜对其进行了研究。我们发现了一种迄今为止未被描述的细胞类型，即网状顶孔细胞，它参与领细胞室内的流量调节。它具有高度多孔的网格状形态，并覆盖顶孔开口。网状顶孔细胞的微小开口呈现开放、中间和关闭状态。这些状态允许对顶孔总开口面积进行逐步调节。在本文中，这三种状态被纳入一项关于流动条件的理论研究中，该研究旨在建立功能性细胞解剖学、流体动力学情况与威廉粗皮海绵中常见的规则身体收缩之间的联系。这为关于旁路元件功能和静水压力在身体收缩中的作用的新假设提供了基础。我们的研究深入了解了海绵管道系统中的局部和整体流动条件，从而增进了当前对相关生理过程的理解。
