Tardigrades have a dorsal brain atop a paired ventral nervous system. (Humans have a dorsal brain and a single dorsal nervous system.) The body cavity of tardigrades is an open hemocoel that touches every cell, allowing efficient nutrition and gas exchange with no need for circulatory or respiratory systems according to "plpnemweb".
- Weak body tendencies, nervous system has large dorsal cerebral ganglion, sub-esophageal ganglion and paired ventral nerve chords
- In addition, they have Brains with lateral lobes connected by two circumpharyngeal cords to a subpharyngeal ganglion.
- Sense organs:
- (1. A pair of red or black pigment eyespots on the head.
- (2. Tactile cirri on head.
- On your left here you can see an Organization of the Nervous System in the Tardigrade Macrobiotus.
- Also to your left, you can see a detailed scan of a Tardigrades Brain.