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First published online February 29, 2008
Journal of Experimental Biology 211, 989-999 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.013078
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Is a convergently derived muscle-activity pattern driving novel raking behaviours in teleost fishes?

Nicolai Konow* and Christopher P. J. Sanford

Department of Biology, 114 Hofstra University, Hempstead, NY 11549, USA


Figure 1
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  		Fig. 1. Diagram of the tongue-bite apparatus (TBA) in a generalized teleost head model, illustrating the five muscles sampled using electromyography in this study. The cleithrobranchial ligament [CBL; situated within the sternohyoideus (SH) muscle] and the positions where two sonomicrometric crystals (1, 2) were sutured to monitor relative CBL distance during feeding in O. mykiss are shown. Other muscle labelling: AM, adductor mandibularis; EP, epaxialis; HP, hypaxialis; PH, protactor hyoideus. Bone labelling: bh, basihyal; co, coracoid; md, mandible; nc, neurocranium; pcl, post-cleithrum; scl, supracleithrum; v, vertebral column.

 

Figure 2
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  		Fig. 2. Rectified electromyograms representing typical raw data from feeding behaviours in O. mykiss (left) and S. jardinii (right). Data for five sampled muscles are shown: SH, sternohyoideus; PH, protractor hyoideus; AM, adductor mandibularis; EP, epaxialis; HP, hypaxialis. Measured variables are indicated with brackets: a, activity onset time, relative to EP activity onset (vertical dotted lines); b, activity duration; c, activity mean amplitude [in analyses corrected with highest muscle-specific amplitude (spike) during an experiment]; d, integrated area, an intensity measurement of the area defined by the rectified curve and the baseline of the muscle activity signal (grey shading). In O. mykiss, SH dist. is sonomicrometry data on strain, measured with two piezoelectric electrodes sutured to the ventral coracoid and urohyal keels, at the sternohyoideus origin and insertion. Note that in some rakes (rake 1) SH activity does not equal contraction and SH stretching results from HP or PH activity. In other rakes, exhibiting greater SH activity (rake 2), the initial stretching is compensated for by much higher levels of SH activity. In S. jardinii, isolated chewing behaviour is uncommon and not illustrated, whereas raking is preceded by muscle activity driving a ubiquitous prey repositioning behaviour with EMG profiles closely resembling chewing EMG profiles (see O. mykiss). We only analysed raking EMG data that were clearly distinguished from this early behaviour (by at least 50 ms pause in activity for all muscles; rake A). Less discreet behaviour complexes (rake B) were omitted from analysis.

 

Figure 3
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  		Fig. 3. Box plot of the taxon-specific behavioural muscle-activity data. O. mykiss: (A) strike; (B) rake; (C) chew. S. jardinii: (D) strike, (E) rake. Boxes depict mean data values for one muscle: AM, adductor mandibularis; EP, epaxialis; HP, hypaxialis; PH, protractor hyoideus; SH, sternohyoideus. Horizontal axis: Onset-time (left box margin) relative to EP onset (vertical dotted line) and muscle-activity duration (right box margin). Vertical axis: top dark box, integrated area; bottom light box, mean amplitude as a percentage of maximum muscle burst per implant. Whiskers indicate s.e.m.

 

Figure 4
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  		Fig. 4. (A) Scatter plot of PC1 and PC2 from a principal component analysis on trout data, showing the relationship between prey capture (striking), chewing and raking behaviour MAPs in O. mykiss. (B) PC1 factor scores for each individual (N=5) across all three feeding behaviours, illustrating the stereotypy of raking relative to strike and chew. For muscle abbreviations, see List of abbreviations; on, onset; dur, duration.

 

Figure 5
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  		Fig. 5. Scatter plot of PC1 and PC2 from a principal component analysis on raking data, investigating the behavioural differences between O. mykiss and S. jardinii. For muscle abbreviations, see List of abbreviations; on, onset; dur, duration.

 

Figure 6
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  		Fig. 6. Scatter plot of PC1 and PC2 from a principal component analysis on the covariance matrix of the full dataset showing the distribution and occupation of MAP two dimensional space by the five species-specific behaviours analysed. For muscle abbreviations, see List of abbreviations; on, onset; dur, duration.

 




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