Spineless life forms

Invertebrate animals are strange things - some have skeletons outside their bodies like insects, lobsters, sea urchins, and spiders, and others have some kind of skeleton inside themselves, such as squids and some slugs. Others have none at all (think worms and jelly fishes), and then there are those that build their own house like a skeleton around them (corals).

The drawing above is by one of my favorite biological artists, Ernst Haeckel, who lived at the end of the 19th century. He was an accomplished scientist and drew both animals and plants, and both large and small things. This drawing is of nudibranches, 'naked slugs' or sea slugs, that live in the ocean and often have elaborate appendages on their colorful bodies. I love these animals, and they often look out of this world. There are over 9000 nudobranch photos on Flickr to explore and there are more than 3000 species of sea slugs in the world.  They can be pink, yellow-pointed, dotted, look like plastic toys, or like bursts of icicles. Amazing creatures.