List out eight characteristics that help distinguish a fish from the other vertebrates.

A fish can be distinguished from other vertebrates by possessing the following characteristic features.

• Fishes are completely aquatic animals.
• Locomotion is assisted by paired and unpaired fins.
• Presence of two chambers, branchial or venous heart.
• Single circulation occurs in which the blood passes only once through heart in each complete circuit.
• Presence of meninx primitiva, the only meninx enveloping the central nervous system.
• Presence of well-developed lateral- line sensory system. 
• Eyes are without eyelids and each eyeball is protected by a nictitating membrane.