MASTER THESIS Biomimetic potential of sponge ... - IAP/TU Wien

spicules has somewhat paradoxically been focused almost exclusively on hexactinellid
sponges (Kulchin et al., 2009) (Aizenberg et al., 2004) (Sundar et al., 2003), but (cf. (Müller et
al., 2009a) due to their larger size.
In demosponges, however, the light transmitting properties of spicules are allegedly
involved in far more complex systems than simple guidance of light to “feed” symbionts: A
photosensory system involving spicules has been proposed (Müller et al., 2010). Spicules do
not transmit light with wavelengths shorter than 580 nm (Müller et al., 2010). In this
context, it is interesting to observe some technical details relating to light reception. It was
shown that in seawater light sources and light receivers are most efficiently coupled in a
wavelength region far from the absorption- maximum of the receiver (D'Sa et al., 1999).
Additionally, coupling of emitter and absorber can be tuned more sensibly and more
efficiently at wavelengths far from the maxima of absorption and emission (Müller et al.,
2010). Observing these principles the wavelength spectrum from 580 nm to 600 nm seems
very well suited to be used for a sensitive photoreception system. Further hints to the
importance of these wavelengths come from behavioural experiments: larvae of siliceous
sponges react to light at 440 nm and 600 nm approx. (Leys et al., 2002). More recently, a
luminescent system (luciferin/luciferase) that emits light in the range between 400 nm and
600 nm has been found in sponges (Müller et al., 2006a). Having found a cryptochrome-like
protein (related to a photoreception protein in humans) in Suberites domuncula, Müller and
colleagues (2010) felt confident to propose a sensory system based on three to four
elements: Sunlight or the luminescent system as light sources, the spicular network as
waveguides transmitting light, and cryptochrome as photoreceptor. It should be mentioned
that this sensory systems would not be limited to sunlight as input, since luminescence can
be triggered by various stimuli.
Hierarchical architecture and emerging properties
Principles
One of the highlight principles found in siliceous spicules is structural hierarchy. The
benefits of hierarchical architecture have been recognized early on by engineers, although
no general trend to more stratified structures in engineering seems to exist (Lakes, 1993).
With respect to hierarchy, materials and structures can be classified starting with a
continuum (order 0) to a simple structure (order 1). Real hierarchical architecture therefore
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