Circumferential spicule growth by pericellular silica deposition in the hexactinellid sponge Monorhaphis chuni

Abstract

SUMMARYThe giant basal spicule of the hexactinellid sponge Monorhaphis chuni represents the longest natural siliceous structure on Earth. This spicule is composed of concentrically arranged lamellae that are approximately 10m thick. In the present study, we investigated the formation of outer lamellae on a cellular level using microscopic and spectroscopic techniques. It is shown that the formation of an outermost lamella begins with the association of cell clusters with the surface of the thickening and/or growing spicule. The cells release silica for controlled formation of a lamella. The pericellular (silica) material fuses to a delimited and textured layer of silica with depressions approximately 20-30m in diameter. The newly formed layer initially displays 40m wide, well-structured banded ribbons and only attains its plain surface in a final step. The chemical composition in the depressions was studied using energy dispersive X-ray spectroscopy and by staining with Texas Red. The data suggest that those depressions are the nests for the silica-forming cells and that silica formation starts with a direct association of silicaforming cells with the outer surface of the spicule, where they remain and initiate the development of the next lamellae.

Spicule and flagellated chamber formation in a growth zone of Aphrocallistes vastus (Porifera, Hexactinellida)

“…if they were depositing new silica, and indeed new silica deposition was seen on megascleres and microscleres. Complete labeling of spicules by PDMPO during a short incubation period supports the prevailing model of silicification, that siliceous spicules grow in layers around an axial filament (reviewed by Uriz 2006;Schr€ oder et al 2007;Wang et al 2011). This differs from calcareous sponges in which spicules grow from a seed nucleus either from the center to the tips or from discrete calcification sites (Ilan et al 1996;Sethmann & W€ orheide 2008).…”

“…; Wang et al. ). This differs from calcareous sponges in which spicules grow from a seed nucleus either from the center to the tips or from discrete calcification sites (Ilan et al.…”

A candidate stem-group rossellid (Porifera, Hexactinellida) from the latest Ordovician Anji Biota, China

“…Spicule growth requires secretion by enveloping scleroblasts (Tabachnick et al 2017), and rossellid prostalial pentactins are secreted as hypodermalia before being extruded. A similar process occurs in the secretion of basalia, such as the giant basal spicules of Monorhaphis, in which biosilicification is continued by clusters of surface sclerocytes (Wang et al 2011); however, the Monorhaphis basalia are secreted within the body tissues, with the spicule extending upwards as the sponge grows (Wang et al 2008) over long times scales that can exceed ten thousand years (Jochum et al 2012). In amphidiscophorans and other lophophytous sponges (those anchored by a root tuft), the same process occurs, with the basalia secreted proximally within the body and continuously extruded (Tabachnick et al 2017).…”

Marine Skeletons: Towards Hard Tissue Repair and Regeneration

“…One of the most facinating porous structures belongs to marine sponges. Although they are not calcium carbonates they form excellent 3D structures for bone growth and are flexible if required [ 57 , 58 , 59 , 60 , 61 , 62 , 63 ]. Marine sponges share much in common with multi-cellular tissues ( Figure 3 ).…”