Jovian Skywhale

Submission for the 2016 Creature Cabal
And, yes, even though it was colored on a computer, the base was an ink drawing.
Unbeknownst to most observers, life is really very hardy. If it can gain a foothold, it can endure pretty much anything anywhere. Nowhere is this more observant than on the worlds without a solid ground, like our own planet Jupiter.
It's impossible to say how the first microbes spawned here, considering that, as a gas planet, there is no ocean nor volcanic activity. Somehow, though, it started, and from a small few survivors came a wild menagerie of different creatures suited to life off the ground.
This, depicted above, is the largest yet seen. Four hundred feet long, its thick exoskeleton provides protection against the planet's hostile pressures below the cloudline. There, it feeds off of the rich methane and ammonia deposits, as well as the occasional straggler from pods of other animals. When full, it rises upwards to bathe in the rich radiation, causing the chemicals to react and release their energy into the animal's system. Then it submerges, restarting the process and bringing more terror to the onlookers below.

Rendered in Ink, Edited in Photoshop