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Sponges are among the most ancient of multicellular animals still living on our blue planet today.
Ecologically and economically, they are among the most highly successful life forms that have ever
existed. First known from the Precambrian, with first reef-building forms appearing in the Cambrian,
they were the major reef builders during the Palaeozoic and Mesozoic Eras. Nowadays they are highly
diverse and we estimate about 15,000 species living in all Recent marine and freshwater habitats
worldwide.
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Phylum Porifera (sponges) are basal metazoans that possess choanocyte chambers, containing flagellated
cells that produce a water current through a system of canals and pores. Sponges lack a differentiation
in distinct tissues and all functions of the body are carried out by mobile cells. They possess
siliceous or calcitic spicules in many but not all species.
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The thought-to-be "class" Sclerospongiae (or coralline sponges as we like to call them) is now
considered to be polyphyletic, with the coralline basal skeleton clearly shown to be a convergent
feature. However, coralline sponges were important reef-building organisms throughout the Earth's
History and provide a "window into the past" for studying e.g. ancestral biocalcification processes.
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Four sponge classes are currently recognised. However, the monophyly and existence of 'Phylum Porifera'
has recently been challenged by genetic data. Three classes have Recent species:
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- Hexactinellida; characterized by a syncytial choanoderm, discrete cells and pinacoderm, siliceous
triaxone spicules, occuring mostly in deeper water.
- Demospongiae; characterized by discrete cells and siliceous monaxone or tetraxone spicules, or
total absence of a mineral skeleton.
- Calcarea; characterized by discrete cells and calcareous spicules
- Archaeocyatha; an important group of sessile marine organisms during the Cambrian, with a rigid
calcareous skeleton. Now presumed to be extinct.
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My research interests concern mainly (see subheadings on top):
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- Calcarea
- GBR Calcarea
- Coralline Sponges
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