Lab 5 - Roach Escape Behavior (1)
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School
University of California, Merced**We aren't endorsed by this school
Course
BIO 170L
Subject
Biology
Date
Dec 19, 2024
Pages
5
Uploaded by bruhsgg
Bio 170 Escape behaviors in Cockroaches Introduction The predominant characteristics of the cockroach central nervous system (CNS) are its segmented nature and decentralization of control processes. The brain, thoracic, and abdominal ganglia are joined together by paired interganglionic connectives to form the ventral nerve cord (VNC). The ability of the cockroach to detect and suddenly respond to an approaching predator (foot, hand, etc.) has been attributed to a reflex circuit that consists of the cerci and giant fiber system. The cerci are a pair of horn-like, wind-sensitive structures located on the end of the abdomen (Figure below). The ventral surface of each cercus contains filiform (thread) hairs that are organized into columns. These columns can be consistently identified in different animals according to the response properties of the associated receptor cell and axon. Each hair is in a socket that allows it to bend most readily in one plane that is column specific. Movement of the hair in one direction along its plane induces a depolarization in the receptor cell and a burst of action potentials (APs) in the sensory neuron. Movement in the opposite direction inhibits any ongoing spontaneous APs. The preferred plane of deflection and directionality of the response is different in each column. Thus, the filiform hair-receptor complexes are responsible not only for detecting the movement of air but also for 'coding', in the form of APs, the direction from which the air current originated. Processing of this information by the CNS results in an 'appropriate' escape response. This functional, columnar specificity of the sensory hairs is preserved from animal to animal. The behavioral latency of the escape response of cockroaches is one of the shortest of any animal. Behavioral latency is the time between the arrival of a stimulus at a mechanoreceptor and the initiation of an escape response. In experiments using high speed cinematography to record the attempted escape from an attacking toad, the cockroach was observed to begin its turn away from the toad in about 40 msec (time) from beginning of tongue extension to cockroach movement. Using controlled wind puffs, the behavioral latency could be reduced to 11 msec. Other experiments revealed that a minimum wind puff velocity of 12 mm/msec (with an acceleration of 600 mm/msec2) can evoke an escape response, while even lower velocities (3 mm/sec) caused slowly walking cockroaches to stop moving. The strong correlation that typically exists between giant fiber systems and escape behavior has been well documented. In instances where a particular cell is necessary and sufficient to evoke a particular behavior the cell is referred to as a command neuron. Giant interneurons (GIs) in the wind escape circuit of roaches are not necessary for the reflex. Animals that have experimentally ablated GIs still exhibit the escape behavior therefore these GIs are not considered command neurons. Severing cervical connectives that are rostral to the sensorimotor circuit also influences the behavior, indicating that descending input from the brain has an effect on the direction of escape. These aspects of fine control and redundancy are paramount to the organism's survival and are complemented by neurochemical modulation via biogenic amines. Text and figure from: Titlow, J. S., Majeed, Z. R., Hartman, H. B., Burns, E., Cooper, R. L. Neural Circuit Recording from an Intact Cockroach Nervous System. J. Vis. Exp. (81), e50584, doi:10.3791/50584 (2013).
Materials Live Dubia roaches Gum orthowax or beeswax Two electrodes (Teflon-coated wires with stripped tips) Hypodermic needle Plastic forceps, dissecting foreceps, dissecting scissors Oscilloscope Dissecting scope Pre-amplifier and cable Hot plate 50ml beaker Pipette and serological tip Protocol 1.Begin by melting beeswax in a 50ml beaker using a hot plate. 2.Retrieve a roach from the container. Using tweezers or your fingers, hold the roach upside down. 3.Pour enough molten hot wax on the inside of a petri dish to cover a large enough area to encompass the roach, but not deep enough to submerge it. 4.Immediately after pouring, place the roach face up on the cooled, but still molten, wax. Position it so that the cerci are not submerged in the wax. 5.Ensure that the roach’sthorax and abdomen are not submerged and still accessible once the wax hardens. 6.Using a hypodermic needle, poke through the exoskeleton in the abdomen and thorax area, and insert the electrodes into the roach. See appendix for diagram of roach neural bundles. 7.Ensure the following settings are selected for the oscilloscope and pre-amplifier: Pre-amplifier: •Lead wires attached to G2 (black wire) and COM (white wire). •Filters: Low = 300 Hz High = 10 kHz •Amplification (Gain): 10 •Cable attached from pre-amplifier OUT to oscilloscope Chanel 1 IN Oscilloscope: •Mode: Channel 1 •Input setting: AC •Volts/Delay: 5 ms
8.Puff air in the direction of the cerci, and observe changes in the amplitude on the oscilloscope screen as roaches respond to the stimulus. Record observations. 9.Touch the cerci with a pipette tip, and observe changes. Record observations.
Once a successful preparation is made and experiments are performed, use the recorded observations to answer the following questions: 1.How do different stimuli affect the frequency and amplitude of nerve impulses? Describe the different stimuli tested and the results. Frequencies that were recorded during the process resulted in similar nerve impulse amplitudes, when you take the stimulus away the amplitude in the graphs had shown to be reduced. 2.What role do the cerci play in the evasion response of cockroaches? Cerci detect movement caused by changes to air, as they are sensitive to air pressure changes, so they can track movement and evade at the same time. 3.What feature of the cerci help roaches to determine the direction of possible predators? The hair sensors on the cockroaches’cerci are what helps in the determination of direction 4.Why is the 6thabdominal ganglion examined in the experiment? Observation of the 6th abdominal ganglion is what helps in the controlling of motor movement , so we can use it observe how cockroaches would react to motor movement stimulus.
Appendix