This is part of a series of questions about biological hydraulics, the fist one being here.
My tetrapods have hydraulics in the thighs of their hind legs. To push or pull fluid from closed chambers in the legs, muscles are going to contract either in the legs themselves or the abdomen.
As hydraulic fluid, I am thinking of using either blood or lymph from the circulatory or lymphatic system, as both are closed. Alternatively, there could be a reservoir for the sole purpose of storing hydraulic fluid, but I am unsure over the efficiency with this.
All of them have the following in common:
- Four chambered heart
- Warm blood
- A closed circulatory and a separate closed lymphatic-like system
- A two chambered lymphatic heart-like organ below the true heart to pump lymph
- Small, rigid lungs with a unidirectional pattern of breathing
- Four respiratory airsacs
- Endoskeleton with four limbs, a skull, and one to two tails
Arthropods and some other invertebrates do use their hemolymph to push themselves, but I am unsure of whether this will change for vertebrates with complex hearts and closed circulatory systems.