posterior root the posterior, or sensory, division of each spinal nerve, attached centrally to the spinal cord and joining peripherally with the anterior root to form the nerve before it emerges from the intervertebral foramen; each posterior root bears a spinal ganglion that conveys sensory fibers to the spinal cord.he sensory division of each spinal nerve, attached centrally to the spinal cord and joining peripherally with the ventral root to form the nerve before it emerges from the intervertebral foramen.
Most published information about the life span of saltwater fish are from public aquariums where the fish are kept in the best possible conditions. Many saltwater fish succumb to illness early in life due to poor husbandry. Some saltwater species only live an average of 2 to 4 years.
Some of them, at a later stage, form large groups living together, but normally are solitary, and some of them act as cleaner fish. Sexual maturity is reached after about 1 year of life. Butterflyfish lifespan is about 3 or more years, with bigger species living longer. The home range of butterflyfish depends on the species, varying from a few square meters to very large territories, which is mainly dependent on food availability.