I really like this shot. It's an interesting perspective on an object. I would have considered perhaps three changes... Possibly remove the small plant in front of the mushroom, possibly use some tin-foil or something similar to reflect a little more light under the mushroom, and possibly remove the out-of-focus object in the lower left corner.
A lot of people are drawn to brighter objects and in this photo it is the top of the mushroom and the out-of-focus object in lower left. Removing this object and lighting the underside of the mushroom slightly would have kept my focus on the mushroom more - it looks like there is a lot of detail and texture underneath to look at but it's a little difficult.
Some variety of Boletus? Impressive composition, focus, and exposure considering the "setup." As I remember you're in competition with some worms/larvae which seem to be already resident in the mushroom even as it sprouts.
Great shot! dof and everything, i cant find anything wrong. But! since there are almost 300 submissions, its hard to place high, not to say that you wont. 8