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Melibe Swimming

Pattern Generation and Neuromodulation
In order to produce a rhythmic behavior, such as swimming, feeding and walking, neurons are wired together into central pattern generating networks or CPGs. Invertebrate nervous systems are particularly well suited for studies of CPGs because discrete ganglia can be studied in vitro and the neurons in these ganglia are very large and identifiable. This makes it possible to investigate the same cells and networks from one animal to the next.

At the present time, along with students in my laboratory, I am investigating the CPGs which produce rhythmic feeding, swallowing and swimming behaviors in the nudibranch, Melibe leonina. We have identified the CPGs in the brain and buccal ganglia which produce the swimming and swallowing behaviors but the location of the feeding CPG is still in question.

Once we have identified the neural networks that produce a given behavior it becomes possible to study how these networks interact with each other (behavioral choice) and how they are modulated and turned on and off.

Swimming behavior
A number of different molluscs swim and the neural basis of swimming has been investigated in several different species, such as Clione, Tritonia, Pleurobranchaea and Aplysia brasiliana. Swimming in Melibe is different from all of these species because they use lateral bending motions to propell themselves, rather than flapping their parapodia or undulating in a dorsal-ventral direction. These two movies below show illustrate two examples of Melibe swimming:

movie 1
movie 2

Melibe swim spontaneously, and in response to contact with a potential predatory, such as a predatory starfish. Spontaneous swimming appears to be influenced by light, and time of day (see figure). Swimming, in intact animals and isolated brains, appears to be inhibited by light (see Figure 5).