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Barbara Zielinski2, Réjean Dubuc3, Weiming Li4
2Dept. of Integrative Biology and Great Lakes Institute for Environmental Research,
University of Windsor, Windsor, ON, N9B 3P4
3Dept. of Neuroscience, Université de Montréal, Montréal, QC, H3P 3P8
4Dept of Fisheries and Wildlife, Michigan State University. East Lansing, MI 48824
The goal of this project was to provide new biological tools for sea lamprey population management, by establishing which molecules are most effective at activating the different solitary chemosensory cell (SCC) populations and inducing motor behaviour. Neural activity was recorded from cutaneous papillae containing SCCs located around the mouth, nasal pore, gill and on the dorsal tail fin (1, 2, 3). Chemo-stimulatory substances included sialic acid, glycine, proline, serine, glutamate, histidine, taurocholic acid, as well as water in which dead trout had been thawed (“dead trout water”). The neural stimulation of brain regions that regulate movement was investigated by recording neural activity from reticulospinal cells of the middle rhobencephalic reticular nucleus (1). Activity in this brain region was observed following the electrical stimulation of cutaneous papillae containing SCCs or papillar nerves – the glossopharyngeal nerve and the vagus nerve (2). The application of the dead trout water onto these papillae also stimulated reticulospinal cell responses. Neuronal tract tracing of the pathway from the neural inputs in the papillae to brain locomotor command neurons confirmed that there is a prominent neural link between these chemosensory cutaneous papillae and locomotor control centers in the brain. This is a di-synaptic neural connection that utilizes the neurotransmitter glutamate (3). The chemostimulatory molecules within the “dead trout water” were identified through activity-guided fractionation. The bile acid, taurocholic acid and 498 g/mol bile acid derivatives (taurodeoxycholic acid, taurohyodeoxycholic acid, taurochenodeoxycholic acid or tauroursodeoxycholic acid) as well as possibly the fatty acid 2-hydroxyocatdecanoic acid were identified in fractions prepared from this dead trout water (3). Synthetic analogues of each compound elicited robust neural responses from the dermal papillae (3). Components of the lamprey alarm substance (creatine, hypoxanthine and inosine) also evoked chemosensory neural responses from the dermal papillae. These neural chemosensory responses suggest that lampreys utilize chemosensory input from dermal papillae for regulating movement during feeding, spawning migration and reproduction. This project describes a non-olfactory chemosensory modality that sea lamprey abatement strategies can utilize as a method of attracting or repelling sea lampreys either independently or in conjunction with previously developed th olfactory-based strategies.