The biological utilization of dissolved silicon (DSi) influences ocean ecology and biogeochemistry. In the deep sea, hexactinellid sponges are major DSi consumers that remain poorly understood. Their DSi consumption departs from the Michaelis-Menten kinetics of shallow-water demosponges and appears particularly maladapted to incorporating DSi from the modest concentrations typical of the modern ocean. Why did sponges not adapt to the shrinking DSi availability that followed diatom expansion some 100 to 65 million years ago? We propose that sponges incorporate DSi combining passive (aquaglyceroporins) and active (ArsB) transporters, while only active transporters (SITs) operate in diatoms and choanoflagellates. Evolution of greater silicon transport efficiency appears constrained by the additional role of aquaglyceroporins in transporting essential metalloids other than silicon. We discuss the possibility that lower energy costs may have driven replacement of ancestral SITs by less efficient aquaglyceroporins, and discuss the functional implications of conservation of aquaglyceroporin-mediated DSi utilization in vertebrates.

溶解硅（DSi）的生物利用影响海洋生态和生物地球化学。在深海中，六线海绵是 DSi 的主要消费者，但人们对其知之甚少。它们的 DSi 消耗量与浅水海绵海绵的 Michaelis-Menten 动力学不同，并且似乎特别不适应吸收现代海洋中典型的中等浓度的 DSi。为什么海绵没有适应大约 100 至 6500 万年前硅藻扩张后 DSi 可用性的减少？我们认为海绵结合了被动（水甘油孔蛋白）和主动（ArsB）转运蛋白的 DSi，而硅藻和领鞭毛虫中只有主动转运蛋白（SIT）起作用。更高的硅运输效率的发展似乎受到水甘油孔蛋白在运输除硅之外的重要准金属方面的额外作用的限制。我们讨论了较低的能源成本可能促使祖先的 SIT 被效率较低的水甘油孔蛋白取代的可能性，并讨论了水甘油孔蛋白介导的 DSi 在脊椎动物中的保护的功能意义。