Select the search type
 
  • Site
  • Web
Search

Student Project

Minimize
Geodia globostellifera Carter, 1880
Species Factsheet: A focus on spicule morphology


Jenny Shiau 2018

Summary
I am steady as a rock, but I’m not a rock. I can move quickly when I’m small, yet I have no organs. What am I but a humble sponge. I am Geodia globostellifera, a sessile marine sponge that lives on the ocean floor and can be found in warm tropical and temperate waters of Australia (Cárdenas et al. 2011; Uriz 2002). This species of sponge belongs to the class of Demonspongiae and is nested within the Tetractinellida (Astrophorida) order (Cárdenas et al. 2011; Hooper and van Soest 2002). G. globostellifera are rough and hard in texture and can be a creamy white to dark brown in colour (Uriz 2002). The sponge’s hard outer layer is notoriously known to be covered in sterraster spicules, which are small glasslike skeletons of the sponge (Schoeppler et al. 2017). Identifying G. globostellifera can be hard. However, thanks to its diverse mineralised skeleton structure, G. globostellifera can be identified with the proper dichotomous key and description.

Although not much is known about this species, G. globostellifera is the first within its genera to be recently identified as having anti-cancer properties that can be used in biomedical science (Feussner et al. 2012; Tabudravu and Jaspars 2001). Additionally, current molecular studies still have much to reveal about the genera’s evolutionary history (Cárdenas et al. 2010). These advances in science are rapidly on the rise to answer questions of this cryptic species. G. globostellifera may not be the most attractive animal, but it certainly has the most potential of them all.
1
Figure 1

Physical Description

Overall
General Appearance 
G. globostellifera are massively encrusting sponges that can be found in different shapes and sizes (Soest and Beglinger 2008). Their sizes can range from several cm in diameter (Carter 1880; Soest and Beglinger 2008; Uriz 2002). They often can be found with shells, coral rubbles, stones and typical detritus embedded on the surface of the sponge along with signs of biofouling (Fig. 1)(Carter 1880; Łukowiak 2015; Soest and Beglinger 2008; Uriz 2002). These sponges are rough to the touch with a relatively smooth surface with oxea spicules (see spicule analysis) protruding from the surface (Fig. 2). Generally, these sponges have a cream to a greyish colour, however, the colour can range from white to dark brown depending on the amount of light exposure (Uriz 2002). G. globostellifera may not seem all too exciting, yet they have the amazing ability to produce strong outer ectosomal layer to protect their internal bodies from harm (Bergquist 1978; Hooper 2000; Uriz 2002).

The Ectosomal Layer
The outer layer of the sponge, or the ectosomal layer, is made up of a dermal cortex that is 0.5 to 1.5mm in thickness (Fig. 3A) (Bergquist 1978; Carter 1880; Hooper 2000; Soest and Beglinger 2008; Uriz 2002). In particular, G. globostellifera have a special organisation of ectosomal skeleton or microscleres that are bound together by epithelial cells that inhabit this region for rigidity (Soest and Beglinger 2008; Uriz 2002). Within this layer lies the exhalant and inhalant holes (oscules) that allows the sponge to use its aquiferous system to filter feed (Fig. 3B, C) (Bergquist 1978; Hooper 2000; Hooper et al. 2002; Soest and Beglinger 2008). These oscules often form separate clusters for exhalant (oscula) and inhalant (ostia) pores called sieve-plates (Hooper 2000). It is also within the separate arrangement of oscules that makes G. globostellifera having a cribriporal orifices that are crucial in characterising this species (Uriz 2002). Likewise, the internal anatomy and arrangement are also used to characterise G. globostellifera.