Behavioral study of P. californica turn behavior
Performed by a team of undergraduates J.K. Wenzel, C.W. Anthony and L. Lane
and a graduate student L.S. Yafremava
Pleurobranchaea Feeding Orientation
Diverse studies have elucidated the computations for directional behavior in arthropods and fish, but few have examined elements of foraging behavior in molluscs. Further, to our knowledge none have quantitatively studied the interactions of sensation and internal state for which these model systems are useful.
We used the predatory sea-slug Pleurobranchaea californica to study the relationships between stimulus location, stimulus amplitude and modality, and internal state on orienting and avoidance turns. Pleurobranchaea is an opportunistic predator on numerous invertebrates, including conspecifics, whose abilities to track appetitive chemotactile stimuli and to recognize and avoid potentially dangerous stimuli must be most critical to the animal’s eventual reproductive success. This species generally inhabits deeper waters (from 20 to >1000 meters) characterized by constantly changing currents. Without external eyes and imaging vision, it depends largely on chemotactile cues as it interacts with the environment.
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Orientation to Betaine Stimuli (5.2 Mb) Experiments were conducted to determine if a relationship exists between the stimulus locus on the chemosensory oral veil to the angle of the animal's orienting turn. Gelatin cubes of 3-5 mm on a side infused with various stimulants were used for chemotactile stimulation. Red food color (Red #40) was added to improve visibility for video data analysis. Chemotactile stimuli were applied to nine distinct points on the oral veil. While applying a stimulus, the animal's turn was video recorded, and after the data was gathered, the video recordings were analyzed. Two kinds of experiments were conducted: single-point applications and two-point applications. One representative recording of a two-point application is shown in this movie. |
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To study both orienting and avoidance, two kinds of
chemical stimuli were used to make the gelatin cubes: appetitive (betaine)
and aversive (taurine) ones. I case of one-point applications a linear relationship
was found to exist between the application locus x and the angle of
turn a for
both stimulants (betaine: correlation coefficient r=0.99, n=9, p<0.001,
taurine: r=-0.93, n=9, p<0.001) |
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The data also indicate that with high level of confidence (P>=90%) there is a correlation between the slope of the linear relationship and concentration of betaine. (correlation coefficient r = 0.91, n = 5, p = 0.0326) |
