Morphological examination of the cirri and papillae in the oyster toadfish, Opsanus tau

The oyster toadfish, Opsanus tau, has been an important model organism for biomedical studies on muscle and sensory physiology.  However, the function of large, fleshy multilobed protuberances called cirri that project from the head and jaw of the fish remains unknown. Additionally, the role of more simplified protuberances termed papillae that project from the head and are localized around neuromasts on the anterior lateral line has yet to be determined.  Preliminary research using light microscopy has indicated that the cirri, especially those protruding from the mandibular surface, may play a role in gustatory function. Bulk labeling of the nerves innervating these cirri, revealed that the nerves project to the gustatory nuclei. The papillae do not appear to serve in a gustatory role but seem to protect putative canal neuromasts of the anterior lateral line that would normally be imbedded throughout the epidermis. Scanning electron micrographs reveal that the hair cells are oriented perpendicular to the axis of the papillae, indicating that the papillae may act to channel the water over the neuromasts, allowing these superficial neuromasts to function in the same way as canal neuromasts. It is hypothesized that the canal neuromasts project to the surface to prevent being impacted by the mud and silt of the toadfish habitat and that the papillae aid in keeping these neuromasts free of sediment.