sea lamprey – NOAA
MADRID, April 18 (EUROPA PRESS) –
In Nature magazine Evidence has been presented for the presence of a rudimentary sympathetic nervous system in lampreys, which was thought to be exclusive to jawed vertebrates.
The finding may prompt us to rethink the origins of the sympathetic nervous system, which operates without the need for conscious thought and controls the fight or flight reaction: a physiological response to the perception of harm, attack, or threat to survival.
The sympathetic nervous system is thought to have evolved in jawed vertebrates and, as such, lampreys were thought to lack one. However, Marianne Bronner of the California Institute of Technology and her colleagues have discovered pairs of sympathetic neuron bundles that extend down the trunk of the sea lamprey larva in a chain-like arrangement.
This rudimentary sympathetic nervous system is derived from an embryonic structure called the neural crest, they show. The neural crest is a transient population of migratory stem cells that gives rise to many key vertebrate structures.
Although many of these features were present in ancestral jawless vertebrates, it is generally believed that others, such as jaws and the sympathetic nervous system, emerged laterin vertebrates with jaws.
The findings here challenge the view that the sympathetic nervous system arose in vertebrates with jaws and lamprey and other jawless vertebrates stand out as important models to understand the emergence of complex vertebrate characteristics.
