Porifera Hexactinellida

• The 'glass' sponges
• Variation from basic sponge - silica spicules form framework between which living tissue is suspended like a cobweb, with mesophyll absent/minimal, no pinacoderm and no choanocytes
• Skeleton made of 4 and 6 pointed siliceous spicules
• mainly pale and deep sea
• long lived (more than 15000 years)
• Pheronema sp. at 1200m depth in the porcupine sea bight, NE Atlantic

  It is so productive at these depths that the sediment at the seabed is composed of siliceous sponges.
• Darwin’s Paradox (1842): How can such high production flourish in such nutrient poor conditions?2013: Dutch scientists showed that the immense filtering capacity of reef sponges effectively recyclednearly all the nutrients and organic matter produced by other reef organisms by capturing it andturning it into sponge tissue that was then grazed on by molluscs, crustaceans and fish!