Journal of Applied and Natural Science 2(2):251-257(2010)
Origin and peripheral distribution of the thoracic and abdominal median nerves in the fifth instar larva of the silkworm, Bombyx mori (Lepidoptera: Bombycidae)
Department of Zoology, Smt. N.P.S. Government College for Women, Chittoor-517 002 (A.P.), INDIA
Abstract : The origin and peripheral distribution of the median nerves of the prothoracic and sixth abdominal ganglia have been traced using methylene blue staining technique. Each median nerve (MN), after originating from the posterior part of the ganglion, bifurcates into two transverse nerves (TN) that extend laterally into the right and left halves of the hemi- segment. The TN of thoracic median nerve bears two motor branches that innervate spiracular muscles and dorsolateral muscles, while the TN of sixth abdominal ganglion bears five motor branches and two sensory branches. Its motor branches innervate three groups of muscles, namely, musculi laterales interni, musculi dorsales interni laterales and musculi dorsales interni mediales, while its sensory branches extend over the body wall in the ventrolateral and dorsolateral areas of the hemi-segment. The median nerves are connected to ganglionic nerves by median nerve connectives that facilitate intersegmental coordination. The functional role of median nerves in respiration, blood circulation and intersegmental coordination is discussed keeping in view their projections and innervations.
Keywords : Bombyx mori , Innervation, Median nerve, Silkworm, Transverse nerve