Summary
The innervation of the aesthetasc hairs ofParagrapsus gaimardii differs slightly from that of other decapods described. Each outer flagellum bears from 160 to 170 aesthetascs each of which is innervated by approximately 130 bipolar sensory neurons. Distally the dendrite from each neuron bears two cilia at a ciliary junction. Each ciliary junction lies within an extracellular space and is situated below the base of the aesthetascs. The cilia have a 9+0 structure in their basal region. Just distally this structure becomes disorganized, the A- and B-subfibres separate and the dendrites increase in diameter. There is evidence for the branching of the cilia resulting in approximately 500 sensory endings per aesthetasc.
No cellular processes are present in the distal 3/4 of the aesthetasc lumen. No pores were found in the aesthetasc walls which are “spongy” in appearance and permeable to crystal violet along the distal 3/4 of their length. The environmental significance of the “spongy” wall and the possible function of the cilia in early transmission of stimulus energy are discussed.
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The author is indebted to Prof. B. Johnson and Dr. I. S. Wilson for much helpful discussion and reading the early manuscript and to Prof. D. M. Ross, Dr. K. G. Pearson and Dr. J. C. Tu for reading the final manuscript.
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Snow, P.J. Ultrastructure of the aesthetasc hairs of the littoral decapod,Paragrapsus gaimardii . Z.Zellforsch 138, 489–502 (1973). https://doi.org/10.1007/BF00572292
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DOI: https://doi.org/10.1007/BF00572292