Quartz dissolution by the sponge Chondrosia reniformis (Porifera, Demospongiae)

Abstract

MANY marine organisms etch calcareous substrata¹. Indeed sponges, mainly of the genus Cliona, are important factors in the erosion of calcareous coasts^2,3. Among terrestrial organisms, only a few lichens are known to penetrate siliceous rocks^4,5, an ability unknown in the animal kingdom. The Demospongiae have a siliceous skeleton formed by spicules⁶ of various shapes and sizes, but several species also incorporate sand grains or foreign spicules^7,8. The demosponge Chondrosia reniformis Nardo has no autochtonous spicules but incorporates a wide range of foreign materials in its ectosome^9,10. Here we report that quartz particles are strongly etched and made uniform in size, quickly and with sharp selectivity, the hydrated silica (chalcedony and opal) remaining unaltered. The presence of a thick collagenous ectosome¹¹ suggests that ascorbic acid, the reducing agent in proline hydroxylation, might be involved in quartz etching by C. reniformis.