Conservation of a Tritonia Pedal peptides network in gastropods

Authors

  • Michael J. Baltzley,

    Corresponding author
    1. Biology Department, St. Mary's College of Maryland, St. Mary's City, Maryland, USA
    Current affiliation:
    1. Biology Department, Western Oregon University, Monmouth, Oregon, USA
    • Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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  • Allison Sherman,

    1. Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, USA
    Current affiliation:
    1. Department of Biological Sciences, California State University, Hayward, California, USA
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  • Shaun D. Cain,

    1. Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, USA
    2. Department of Biology, Eastern Oregon University, La Grande, Oregon, USA
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  • Kenneth J. Lohmann

    1. Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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Author for correspondence. E-mail: baltzlem@wou.edu

Abstract

Adults of the nudibranch mollusc Tritonia diomedea crawl using mucociliary locomotion. Crawling is controlled in part by the large Pedal 5 (Pd5) and Pedal 6 (Pd6) neurons that produce TritoniaPedal peptides (TPeps). TPeps elicit an increase in ciliary beat frequency, thereby increasing crawling speed. In adults of T. diomedea, an extensive network of TPep-containing neurites adjacent to the basement membrane of the pedal epithelium delivers TPeps to the ciliated cells. In this study, we show that diverse nudibranchs all have a pattern of TPep-like immunoreactivity similar to that of T. diomedea, with thin tracts of TPep-like immunoreactive (TPep-LIR) neurites projecting to the epithelial layer. We also show that members of two non-nudibranch gastropod species have a pattern of TPep-innervation similar to that of the nudibranchs. In addition, we characterized two pairs of motor neurons in adults of the nudibranch Armina californica that are possible homologues of the Pd5 and Pd6 cells in T. diomedea. Activity in one of these pairs, the Pedal Peptidergic Dorsal 1 (PPD1) cells, was correlated with mucociliary locomotion. The second pair, the Pedal Peptidergic Ventral 1 cells, shared synchronous synaptic input with the PPD1 cells, a pattern consistent with the shared synaptic input of the T. diomedea Pd5 and Pd6 cells. These findings suggest that the roles of the Pd5 and Pd6 cells as mucociliary motor neurons in nudibranchs are conserved evolutionarily. Additionally, the extensive network of TPep-LIR neurites seen in the foot of T. diomedea appears likely to be a common feature among gastropods.

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