Desert Muck Leech

The Desert Muck Leech was a race of simplistic leech creatures living in a puddle on Mars, a puddle which was later paved over for a car park for the new Mars Vegas.

These Leeches are descendants of the Dark Ones, who fought in the Arms Race of Evolution but only one survived the paving of the puddle that they lived in. This one later killed Frida Waterfall and Hutch Waterfall, but it would be killed by an Encyclopod and then gone forever after being eaten by Dr. Zoidberg.

Trivia

 * The Latin name given for the creature is "Cyprinodon martius", which comes from also or in Latin, "Cyprinodon salinus".  The "martius" in the Desert Muck Leech is purely a reference to the fact that it is on Mars.
 * Ken Keeler, writer (specifically of the plot it was involved in), had a personal likeness for this pupfish, which could survive very harsh environments.