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Functional Evaluation of Olfactory Pathways in Living Xenopus Tadpoles
Published on: December 11, 2018
Olfactory projections in the lepidosirenid lungfishes
1Laboratory of Comparative Neurobiology, Scripps Institution of Oceanography and Department of Neurosciences, School of Medicine, University of California San Diego, La Jolla, CA 92093-0201, USA. rgnorthcutt@ucsd.edu
Brain, Behavior and Evolution
|November 10, 2011
Summary
Olfactory bulb projections in lungfish reveal a primitive pattern in bony fishes. This study maps neural pathways, showing extensive connections that are reduced in amphibians.
Area of Science:
- Neuroscience
- Comparative Anatomy
- Evolutionary Biology
Background:
- Understanding olfactory system evolution is key to vertebrate neurobiology.
- Lungfish represent a crucial link between aquatic and terrestrial vertebrates.
Purpose of the Study:
- To experimentally determine olfactory nerve and olfactory bulb projections in lepidosirenid lungfishes.
- To compare lungfish olfactory circuitry with that of other vertebrates, particularly amphibians and bony fishes.
Main Methods:
- Neural tracers (DiI) were used for unilateral injections into the olfactory nerve and accessory and main olfactory bulbs.
- Experimental tracing mapped projections within the brain, including telencephalic, diencephalic, and midbrain centers.
- Cladistic analysis was employed to interpret the evolutionary significance of observed projection patterns.
Main Results:
- Olfactory nerve injections labeled main and accessory olfactory bulbs and terminal nerve fibers projecting to medial hemispheric wall, pallia, and preoptic nuclei.
- Accessory olfactory bulb projections targeted the ipsilateral medial amygdalar nucleus.
- Main olfactory bulb projections innervated most of the ipsilateral telencephalon and showed secondary projections to contralateral olfactory bulb, diencephalon, and midbrain.
Conclusions:
- Lepidosirenid lungfish olfactory projections are extensive and represent a primitive pattern for bony fishes.
- The observed pattern contrasts with the simplified olfactory projections found in amphibians, suggesting a derived state.
- This research provides insights into the evolutionary trajectory of olfactory systems in vertebrates.
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