Meeting Abstract
Nudibranchs rely on mechanosensory and chemosensory detectors for foraging, homing, and location of conspecifics. Despite the studies focused on odor driven behaviors, little is known about the invaginated and ciliated grooves on the oral veil. Prior work indicates that nudibranchs primarily detect odor and flow cues for navigation towards food, mates, and predators with their rhinophores. Our study focuses on the ciliated grooves, a potential boundary-layer sniffing organ that might use similar sensory mechanisms as the rhinophores. Many species of nudibranchs generate ciliary-driven currents between the branches of the clavus of the rhinophore that allows the animal to sample media from up to 5mm away from the organ, likely reducing the olfactory impact of the boundary layer. The ciliated grooves along the oral veil are placed in front of the animal facing downward towards the substrate such that odors trapped in the boundary layer might be actively pulled out of the layer and into the groove. Our results showed that inside the grooves at the lateral ends of the oral veil are dense beds of motile cilia similar to those found on the rhinophores and foot. Video of the ciliated groove using particle image velocimetry shows active particle movement through beating of the cilia. We were able to back trace the nerves from the ciliated groove to the cerebral-pleural complex and the pedal ganglia in Triopha catalinae. Nerves from the cerebral and from the ventral, anterior pedal ganglia innervate the oral groove ipsilaterally. Preliminary recordings and stimulation of the Pd7 neurons in the pedal ganglia have given insight to how the particle flow speed down the grooves may be controlled by modulating the beat frequency of the cilia.
