Wednesday, March 4, 2009

Life Photo Meme: Honor an Invert

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Order: Nautilida

Family: Nautilidae

This nautilus is a strange but beautiful member of the cephalopod family. Unlike its relatives, the squids, cuttlefish, and octopus, the nautilus has an external shell. It also possesses far more tentacles, (up to 90) that have no suckers or hooks of any sort. The hood on top of the nautilus's head is actually made from tow specialized tentacles, and acts as an operculum, or lid, for the shell.

They don't expend much energy swimming, as they relay on the gas filled chambers to keep them afloat. Because of this, they only need to feed once a month. They hunt small fishes and shrimp in the water column but scent. Although they have eyes, their vision is very poor.

Their eyes are a simple pinhole eye without a lens. The lack of a lens means light and images are not focused well on the retina, and water can actually pass into the inside of the eye!

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