Microfossil of the Month: Sponge Spicule
Something a little bit different - this month I have an image of a siliceous sponge spicule! This show up occasionally in my phytolith slides, and are very distinctive. Sponges, or poriferans to give them their scientific name, are characterised by an unusual feeding system that involves drawing water in through little pores in the outer walls, and filtering food from the water as it moves around their bodies, before being pumped back out again. This flow of water occurs in one direction and is driven by beating flagella. Sponge spicules provide structural support and protection from predators. They come in all sorts of shapes each with a different name - the single spike shape that you can see looks like a monaxon, though it is also possible that is has broken off a larger 'polyaxon' type. The formation of spicules seems to be better understand than that of my other favourite siliceous microfossil, the phytolith, and is controlled largely genetically, but with environmental c...