Small, Medium, Big - 3 Species Helping Each Other To Survive
The Big - "Seelan"
These big animals spend their whole life in the clouds. They born and die there. Their organisms can produce Helinium - this element is lighter than air, so they can just hang in the air without moving. Seelans are predators, but when they grow up, they are too big to hunt for birds or other flying organisms. They are just to slow for that. Luckily, when they are getting bigger, they look for some kind of "guests". Old Seelans usually have many organisms living on their body. Frequently these are K'rats and Wozits. They help big creatures to survive in the clouds getting in return a private "island" to live.
[Place to live]

The Medium - "K'rat" aka "Long Neck"
These strange organisms are some kind of parasites. They can be found on big, old Seelans usually attached on their neck. They feed on remains of the big creature' food in exchange for assistance in hunting. They have many eyes to watch the sky, and their saliva can glow with intensive light that lure other flying creatures.
[Luring]

The Small - "Wozit"
These insects are like private fighter squadron. Maybe they are small, but they have very toxic venom in their stings. They can easily kill if it's necessary. Thanks to Seelans they have place to live, so they protect their big living home. They make small nests in the ossified part of the Seelan's skin [usually on the giants' neck]. They fly in around their home looking for threat and also other small organism that are their food.
[Protection]