Neural control of the pyloric region in the foregut of the shrimp Penaeus (Decapoda: Penaeidae)

Abstract

Pyloric pattern-generating neurons that control the pyloric region of the foregut were identified in the stomatogastric ganglion of the most primitive decapod genus Penaeus. Five types of motor neurons and one interneuron are involved in generation of pyloric motor pattern. One cell type of motor neurons innervates muscles of both the gastric mill and the pylorus like the gastric motor neurons in Cancer, but unlike those in Panulirus. These identified neurons are connected to each other either by electrical or inhibitory chemical synapses to construct the neural circuit. This pyloric circuit is similar to the homologous circuit of other crustacean species though some differences are seen in synaptic connections, supporting the hypothesis that the basic design of the neural circuit has been conserved during evolution of the Malacostraca, and that differences have occurred in the synaptic connectivity as the foregut structure has become complex. The motor neurons use either acetylcholine or glutamate as a neurotransmitter like in reptantians. The foregut structure, the number of the pyloric cells, muscle innervation, neurotransmitters, and circuitry are compared among malacostracan crustaceans to provide insight into how the neural circuits change and evolve to produce the motor patterns mediating behaviour.