Peripheral sensory cells in the cephalic sensory organs of Lymnaea stagnalis

Abstract

The peripheral nervous system in gastropods plays a key role in the neural control of behaviors, but is poorly studied in comparison with the central nervous system. Peripheral sensory neurons, although known to be widespread, have been studied in a patchwork fashion across several species, with no comprehensive treatment in any one species. We attempted to remedy this limitation by cataloging peripheral sensory cells in the cephalic sensory organs of Lymnaea stagnalis employing backfills, vital stains, histochemistry, and immunohistochemistry. By using at least two independent methods to corroborate observations, we mapped four different cell types. We have found two different populations of bipolar sensory cells that appear to contain catecholamines(s) and histamine, respectively. Each cell had a peripheral soma, an epithelial process bearing cilia, and a second process projecting to the central nervous system. We also found evidence for two populations of nitric oxide-producing sensory cells, one bipolar, probably projecting centrally, and the second unipolar, with only a single epithelial process and no axon. The various cell types are presumably either mechanosensory or chemosensory, but the complexity of their distributions does not allow formation of hypotheses regarding modality. In addition, our observations indicate that yet more peripheral sensory cell types are present in the cephalic sensory organs of L. stagnalis. These results are an important step toward linking sensory cell morphology to modality. Moreover, our observations emphasize the size of the peripheral nervous system in gastropods, and we suggest that greater emphasis be placed on understanding its role in gastropod neuroethology.

Intrinsic and extrinsic innervation of the heart in zebrafish (Danio rerio)

“…To visualize the intracardiac projections and termination patterns of axons in the cardiac rami of the vagosympathetic trunks, we used a combination of the actively transported neurotracer neurobiotin (SP1120, nlx_152485; RRID AB_2313575; Vector Laboratories, Burlingame, CA; Wyeth and Croll, 2011) and a fluorescent styryl dye, FM1-43X (F35355; Life Technologies). This dye, which appears to label the membranes of recycled synaptic vesicles, becomes concentrated in active synaptic terminals over time (Betz et al, 1992) and so accumulates in the intracardiac terminals of extracardiac axons when those axons are electrically stimulated.…”

Histamine Immunoreactive Elements in the Central and Peripheral Nervous Systems of the Snail, Biomphalaria spp., Intermediate Host for Schistosoma mansoni

“…In the pulmonate snails Lymnaea stagnalis and Helix pomatia , the distribution, uptake, release properties, and possible physiological actions of HA were studied by Hegedus et al [17], who found HA-like immunoreactive (HA-Lir) neuronal cell bodies in most ganglia and fibers in the neuropil of each ganglion, in all connectives, commissures, peripheral nerves, and in several peripheral tissues. Numerous sensory cells in the tentacles, lip, and statocysts of Lymnaea also displayed HA-like immunoreactivity [17][18][19], while administration of an HA antagonist disrupted behaviors involved in the orientation to gravity [19]. …”

Heterochronies in the formation of the nervous and digestive systems in early postlarval development of opisthobranch mollusks: Organization of major organ systems of the arctic dorid Cadlina laevis

“…Nerve CA er fibers innervate the musculature of the body wall, foot, and pharynx. It is obvious that in juve nile specimens of C. laevis, catecholamines can already actively participate in regulation of sensory functions, in the work of musculature and the digestive system, and in feeding behavior, as in the previously studied adult representatives of some species of gastro pods (Quinlan et al, 1997;Hernádi and Elekes, 1999;Croll, 2001;Wyeth and Croll, 2011, et al). A considerable number of epidermal receptor cells, as well as of nerve fibers innervating the musculature of the body wall and notum of the mollusk, are ChAT im.…”