Ascending spinal systems in the fish, Prionotus carolinus

Area of Science:

• Neuroscience
• Comparative Anatomy
• Sensory Biology

Background:

• Sea robins (teleostei) possess pectoral fin rays equipped with chemosensory organs.
• These organs are innervated by spinal nerves, connecting to unique accessory spinal lobes in the rostral spinal cord.

Purpose of the Study:

• To investigate the neural connectivity of the accessory spinal lobes and associated ascending systems in the sea robin, Prionotus carolinus.
• To compare spinal cord pathways in sea robins with those in other vertebrates.

Main Methods:

• Anterograde and retrograde tracing using horseradish peroxidase (HRP) and diI.
• Detailed examination of fiber terminations within the spinal cord, brainstem, midbrain, and thalamus.

Main Results:

• Dorsal root fibers primarily terminate in accessory lobes; some ascend to the lateral funicular complex.
• The lateral funicular complex projects to the medial lemniscus, which ascends through the brainstem, with projections to the inferior olive, reticular formation, torus semicircularis, optic tectum, and thalamus.
• A significant spinocerebellar system projects to the cerebellum.

Conclusions:

• The connectivity of the sea robin spinal cord shows striking similarities to other vertebrates.
• Despite utilizing spinal chemosensation for feeding, sea robins rely on the medial lemniscal system, a pathway common in other vertebrates, for processing this sensory information.