Dynamics of spicule production in the marine sponge Hymeniacidon perlevis during in vitro cell culture and seasonal development in the field

Abstract

To characterize the formation of silica spicules, the dynamics of spiculogenesis of an intertidal marine sponge Hymeniacidon perlevis (Montagu 1818) (Porifera: Demospongiae) were investigated by measuring the gene expression of silicatein (the enzyme responsible for spicule silicification) and the dimensional changes of spicules during the developmental process of individual sponges and in cell cultures of primmorphs of archaeocyte-dominant cell populations. The different developmental stages of spicules were documented by time-lapse microscopy and observed by transmission electron microscopy during a 1-month culture period. During its annual life cycle, H. perlevis has four different developmental stages: dormancy, resuscitation, bloom, and decline. Field-grown individual sponge samples at different stages were collected over 7 months (March to September 2005). The dimensions of the silica spicules from these samples were microscopically measured and statistically analyzed. This analysis and the material properties of the spicules allowed them to be classified into four groups representing the different developmental stages of spiculogenesis. Silicatein expression in the bloom stage was more than 100 times higher than that in the other stages and was correlated with the spicule developmental stage. The trend of spicule formation in field-grown sponges was consistent with the trend in cell culture. A new parameter, the maturation degree (MD) of spicules (defined as the ratio of actual to theoretical silica deposition of mature spicules), was introduced to quantify spicule development. Silica spiculogenesis during H. perlevis development was delineated by comparing MD and silicatein expression.

Analysis of silicatein gene expression and spicule formation in the demosponge Amphimedon queenslandica

“…This finding suggests that silicatein expression is not directly connected with number of spicules, although it should be recognised that these silicatein genes are expressed at high levels before the start of spicule formation. This delay seen in the early stages between silicatein expression and spicule number can be expected as spiculogenesis requires multiple steps before the initial silica deposition, including translation, phosphorylation and self-assembly (Cao et al 2007). This will confound the correlation of expression with spicule number, in addition to the variability observed in both data throughout development.…”

“…3.7). In Hymeniacidon perlevis, it was shown that silicatein expression changed depending on the sampling part of the individual, front, middle or back; each part affected by different micro-environment like water current flow capacity, higher flow resulted in higher expression (Cao et al 2007). Larvae in this study were from a pool of adult sponges collected in different parts of the reef.…”

“…The spicule preparation protocol was performed as described by Cao et al (2007), with some modifications. To maintain the original number of spicules, fixed embryos, larvae and postlarvae were transferred individually on a grid glass slide, in 1-2 µl of 70% ethanol.…”

“…Afterward, silicatein has been isolated from other marine sponges, including Petrosia ficiformis (Pozzolini et al 2004), Hymeniacidon perlevis (Cao et al 2007), Cratomorpha meyeri (Müller et al 2008b), Latrunculia oparinae (Kozhemyako et al 2009) and Geodia cydonium (Müller et al 2007c), as well as freshwater sponges including Lubomirskia baicalensis (Kaluzhnaya et al 2005;Kaluzhnaya et al 2011), Ephydatia fluviatilis (Funayama et al 2005;Mohri et al 2008) and Ephydatia muelleri (Kaluzhnaya et al 2011). …”

“…Silicatein is present specifically in siliceous sponges (demonsponges, hexactinellids and homoscleromorphs) and was first discovered in the axial filament of the demosponge Tethya aurantia where two genes have been isolated, silicatein α and silicatein β (Shimizu et al 1998). Silicatein genes have since been identified in other marine and freshwater sponges (Krasko et al 2000;Pozzolini et al 2004;Cao et al 2007;Kaluzhnaya et al 2005;Funayama et al 2005;Mohri et al 2008).…”