Behavioral Neuroscience, lecture on Aplysia and its behavior
USD Department of Biology
Behavioral Neuroscience
Summers
Aplysia Behavior
Sensory Stimulation of Siphon Withdrawl
Motor Output driving Siphon Withdrawal
Gating
Conditioning & Memory
Aplysia Siphon and Gill text:Kandel pages 1248-1257
Glu
Acetylcholine (ACh)
5-HT
Aplysia and Siphon Withdrawl
Siphon Withdrawl Circuitry
end     Acronyms/Abbreviations     Syllabus
Defensive Behaviors - Siphon Withdrawal
I. Aplysia 			

	A. Sea Hares
	
		1.  Aplysia californica, A. brasiliana, A. dactylomela, A. depilans
			A. extraordinaria, A. fasciata, A. punctata, A. oculifera, 
	
	B. Global Marine invertebrate - mullusca - subclass opisthobranch - order Aplysiacea
	
		1. Low rocky intertidal habitat
		
			a. Herbiverous - feeds on larger algae
		
		2. Large size (> 5 inches), reduced shell (buried in mantle)
		
			a. mantle cavity with gill and siphon
		
			b. purple ink - defensive response
			
		3. Cephalic tentacles - 2 pairs
		
		4. Hermaphroditic
		
			a. both male and female roles in copulation
			
				i. up to 500 million eggs laid at a time
	
	C. Nervous system contains ~20,000 neurons
	
		1. cell bodies mostly in paired bilateral ganglia
		
			a. rostral to caudal: buccal, cerebral, 
			    pleural - dorsal / pedal - ventral, 
				fused abdominal (left)/fused viseral (right)
	
II. Behavior - Siphon withdrawal reflexes

	A. Gill and Siphon reside in Mantle cavity
	
		1. gills absorb O2 from sea H2O
		
			a. also excrete CO2 and ammonia products (NH3)
			
		2. siphon draws oxygenated H2O across gill
		
			a. pumps wastes away from gill
			
	B. Gill and Siphon may be muscularly withdrawn into the mantle to protect them
	
		1. Withdrawal reflex elicited by tactile sensory input
		
			a. electrical stimulation also causes withdrawal
		
	C. Reflex
	
		1. Simplest behavioral response - requires only 3 neurons
		
			a. sensory input
			
				i. often specialized sensory organ
				
					(1) input signal may be graded
				
				ii. afferent (toward central nervous system)
				
			b. interneuron(s)
			
				i. gating
				
				ii. this site is the only possibility for modifying the behavior
				
				iii. enhancing, limiting, delaying, 
				     repeating, priming, learning
				
					(1) may require additional circuits
					
					(2) may require hormonal or 
					    neuropeptide modulation
					
			c. motor output = efferent (away from CNS)
			
				i. always cholinergic (ACh) in vertebrates
	
	D. Tail - Siphon withdrawal reflex
	
		1. defensive response
		
		2. also stimulated by tactile or electrical sensory stimulation

III. Sensory Input