Uriz María-J, Turon Xavier, Becerro Mikel A, Agell Gemma
Center for Advanced Studies (CSIC), Girona, Spain.
Microsc Res Tech. 2003 Nov 1;62(4):279-99. doi: 10.1002/jemt.10395.
Silica deposition is a fundamental process in sponges. Most sponges in the Classes Demospongiae and Hexactinellida secrete siliceous elements, which can subsequently fuse, interlock with each other, or form three-dimensional structures connected by spongin. The resulting skeletal frameworks allow sponges to grow upwards and facilitate water exchange with minimal metabolic cost. Several studies on sponge skeletogenesis have been published. We are beginning to understand the mechanisms of spicule secretion and the role of spicules and skeletal frameworks in the biology, ecology, and evolution of sponges. Molecular techniques and ecological experiments have demonstrated the genetic control of the process and the contribution of environmental factors to the expression of a sponge spicule, respectively. However, other classic topics such as the role of membranes in silicon transport or whether spicules are formed in situ or secreted anywhere in the sponge mesohyl and then transported to the skeletal framework require further investigation. We review the process of silica deposition in sponges at the molecular and cellular levels, as well as the biological and ecological functions of spicules and skeletons. The genetic control of spicule shapes makes them useful in the reconstruction of sponge phylogeny, although recent experiments have demonstrated the influence of environmental factors in modulating spicule size, shape, and the presence or absence of one or more spicule types. The implications of such variations in sponge taxonomy may be important. Besides supporting sponge cells, spicules can help larvae stay buoyant while in the plankton or reach the bottom at settlement, enhance reproduction success, or catch prey. Conversely, the role of spicules and skeletons in deterring predation has not been demonstrated. Knowledge of several aspects is still based on a single or a few species and extrapolations should be made only with caution. With the advent of new molecular techniques, new lines of research are presently open and active in this field.
硅质沉积是海绵动物的一个基本过程。寻常海绵纲和六放海绵纲中的大多数海绵会分泌硅质成分，这些成分随后可能会融合、相互连锁，或形成由海绵硬蛋白连接的三维结构。由此产生的骨骼框架使海绵能够向上生长，并以最小的代谢成本促进水的交换。已经发表了几项关于海绵骨骼发生的研究。我们开始了解骨针分泌的机制以及骨针和骨骼框架在海绵动物的生物学、生态学和进化中的作用。分子技术和生态实验分别证明了该过程的遗传控制以及环境因素对海绵骨针表达的影响。然而，其他一些经典问题，如膜在硅运输中的作用，或者骨针是在原位形成，还是在海绵中胶层的任何部位分泌然后运输到骨骼框架，仍需要进一步研究。我们在分子和细胞水平上综述了海绵动物中硅质沉积的过程，以及骨针和骨骼的生物学和生态功能。骨针形状的遗传控制使其在海绵系统发育重建中很有用，尽管最近的实验表明环境因素对调节骨针大小、形状以及一种或多种骨针类型的有无有影响。这种海绵分类学上的变化可能具有重要意义。除了支撑海绵细胞外，骨针还可以帮助幼虫在浮游阶段保持漂浮状态，或在沉降时到达海底，提高繁殖成功率，或捕获猎物。相反，骨针和骨骼在抵御捕食方面的作用尚未得到证实。目前对几个方面的认识仍然基于单一物种或少数物种，进行推断时应谨慎。随着新分子技术的出现，该领域目前有新的研究方向正在开展且十分活跃。
