Pertsov White Sea Biological Station, Biological Faculty, Lomonosov Moscow State University, 129281, Leninskie gory 1-12, Moscow, Russia.
Pertsov White Sea Biological Station, Biological Faculty, Lomonosov Moscow State University, 129281, Leninskie gory 1-12, Moscow, Russia.
Zoology (Jena). 2022 Feb;150:125984. doi: 10.1016/j.zool.2021.125984. Epub 2021 Dec 7.
Sponges (phylum Porifera) are highly specialized filter-feeding metazoans, pumping and filtering water with a network of canals and chambers, the aquiferous system. Most sponges have a leuconoid aquiferous system, characterized by choanocytes organized in small spherical chambers connected with ambient water by a complex net of canals. Such organization requires substantial pressure difference to drive water through an elaborate system of canals, so the choanocytes in leuconoid sponges have several structural features to generate pressure difference. In contrast, it is generally accepted that asconoid and syconoid sponges with long choanocyte tubes or large choanocyte chambers have no similar structures in their choanocytes. The present study is devoted to the detailed ultrastructural analysis of the choanocytes and their filter apparatus in the asconoid calcareous sponge Leucosolenia variabilis. The general structure of L. variabilis choanocytes is similar to that described for other sponge species. However, the fixation with 0.1% ruthenium red allowed us to reveal for the first time a complex of glycocalyx structures (vanes on the flagella, a fine glycocalyx sealing microvilli in the collar, and a glycocalyx strainer, embedding the apical parts of neighboring collars) in the choanocytes of L. variabilis, which are traditionally associated with the pumping and filtration process in leuconoid demosponges. All revealed glycocalyx structures have dimensions and locations similar to those found in the choanocyte chambers of some demosponges. The data suggest that L. variabilis utilizes the principles of water pumping and filtration similar to those in demosponges and revealed glycocalyx structures are potentially crucial for these processes. It seems that sponges from distant phylogenetic lineages and with different body plans rely on common principles of choanoderm organization for effective pumping and filtration of water. However, while some adaptation for effective pumping and filtration of water have possibly arisen before the diversification of Porifera, others have appeared independently in different lineages.
海绵（多孔动物门）是高度特化的滤食性后生动物，通过一个由运河和腔室组成的网络——水腔系统，泵送和过滤水。大多数海绵具有白细胞样水腔系统，其特征是组织在小的球形腔室中的领细胞，通过一个复杂的运河网络与周围水相连。这种组织需要相当大的压力差来驱动水通过一个精心设计的运河系统，因此白细胞样海绵中的领细胞具有几种结构特征来产生压力差。相比之下，人们普遍认为，具有长领细胞管或大领细胞腔的柱骨海绵和丝盘海绵的领细胞没有类似的结构。本研究致力于详细的超微结构分析柱骨钙质海绵 Leucosolenia variabilis 的领细胞及其过滤装置。L. variabilis 领细胞的一般结构与其他海绵物种描述的结构相似。然而，用 0.1%钌红固定后，我们首次揭示了一种糖萼结构复合物（鞭毛上的叶片、微绒毛领部精细的糖萼密封、糖萼筛，嵌入相邻领部的顶端部分）在 L. variabilis 的领细胞中，这些结构传统上与白细胞样钙质海绵的泵送和过滤过程相关。所有揭示的糖萼结构的尺寸和位置与在一些钙质海绵的领细胞室中发现的相似。这些数据表明，L. variabilis 利用与 demosponges 相似的水泵送和过滤原理，并且揭示的糖萼结构对于这些过程可能至关重要。似乎来自不同系统发育谱系和具有不同身体计划的海绵依赖于共同的领细胞组织原则，以实现水的有效泵送和过滤。然而，虽然一些有效的水泵送和过滤的适应可能在多孔动物门多样化之前就已经出现，但其他适应是在不同的谱系中独立出现的。
