The peripheral nervous and muscular systems of the tick Argas arboreus

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Abstract
The peripheral nervous system of A. arboreus females was described from transverse and longitudinal serial sections of whole ticks. The muscle and integumental discs also were described and numbered, since the former constitute major nerve terminations; the latter serve as sites for muscle attachment and important topographical landmarks. There were 11 cranial nerves and 2 noncranial nerves. The medial nerve was formed as a result of the union of branches from the 5th, 6th, 7th, 8th, 9th and 10th cranial nerves. The lateral nerve resulted from the union of branches from the 1st and 8th cranial nerves and from the medial nerve. All the nerves were paired except the pharyngeal nerve which was single. All nerves supplied nerve branches to muscles. Richly innervated structures of the body included the junction between the dorsal and ventral integument, the vaginal wall, the salivary gland, the ventral optic organ, the stomach wall and the anal region. The ovary, the glandular part of Gene''s organ and the glandular part of the coxal organ appeared to receive no direct nerve supply. Besides a fibrous supply from the neuropile, the neurilemma received a nerve branch from the salivary division of the palposalivary nerve. A nerve branch from the 2nd pedal nerve terminated in the viscerocoelomic space between the 2 membranes constituting the perineural sinus wall. Another branch from the 2nd pedal nerve supplied an integumental acellular corpuscular structure located in the ventral integument between coxae I and II. More than 10 ganglia were associated with the optic nerve, 7 with the palposalivary nerve, 6 with each of the 4 pedal nerves, 2 with the cheliceral nerve and 1 with each of the opisthosomal and esophageal nerves. In 2 cases ganglia provided attachment for muscles. The esophageal ganglion and 1 cheliceral ganglion provided insertion sites for 1 perineural sinus muscle and 1 cheliceral muscle both of which had their origin in the integument. Aggregates of cells, possibly neuronal, were detected at the terminal ends of the cheliceral, pharyngeal, palpal division of the palposalivary and pedal nerves; fibers appeared to extend from these cells to more distal surface structures. Comparable aggregates of cells with no apparent nerve supply were also detected along the side of the buccal canal and the hypostome with their fibers also extending to more distal surface structures.