Figure 1.
Panel A shows a single frame from a high-speed movie of a 14 dpf larva that is pursuing a prey item, in this case a paramecium. In panel B, ten landmarks have been manually placed on the larva and prey. Panel C shows the resulting point-and-line representation of the larva and prey, with numbers automatically assigned to each point. The XY coordinates of each point are shown in panel D, along with automatically extracted information on the larva's fins, tail, and position relative to the paramecium. Panel E shows a portion of the overall pursuit and capture event, indicating the tail bend, extension of each fin, and distance and bearing to the paramecium through time. The arrow indicates the frame represented in panels A–D. Scale bar in A represents 1 mm.
Figure 2.
Overall structure of larval startle.
The bearing (0° at t = 0), tail bend angle, and pectoral fin extensions are shown for the entirety of a response to a startling auditory stimulus (Panel A). Individual frames from the behavior are shown in Panels B–I), with accompanying timestamps. The approximate time for each of these frames is indicated by an arrow in Panel A. This startle event is composed of three phases, a rapid high-amplitude bend of the tail (C-bend), a strong counter bend and tail beat (fast swim), and then a slower, less dramatic alternating tail beat accompanied by pectoral fin extensions (slow swim). Scale bar in B represents 1 mm. The larva shown is 7 dpf.
Figure 3.
Pectoral fin involvement in long-latency, but not short-latency startle.
Charts representing typical short-latency (Panel A) and long-latency (Panel B) startle responses are shown. In short-latency startle responses, the fins remain adducted during the C-bend and counter bend. Both pectoral fins are abducted and adducted in unison during the C-bend and counter bend of long-latency startles. Individual frames from a short-latency (Panel C) and a long-latency startle (Panel D) are shown, with the approximate times of the frames indicated by the arrows in Panels A and B. Panel E shows a scatter plot of startle events with and without fin involvement, and the latency to respond to the stimulus. n = 9 for responses with active fins and 10 for inactive fins, and p<0.0001 (two-tailed unpaired t-test). Scale bars in C and D indicate 1 mm. The larvae shown are 7 dpf.
Figure 4.
The chart in panel A shows a larva's pursuit and capture of a paramecium (arrow, B). The individual elements of the behavior are indicated by red lines. Panels B–I show individual frames from the movie of this sequence, with approximate times of the frames indicated by arrows in Panel A. The paramecium is indicated with an arrow in panel B, and all panels show the same field of view. Panels B and C show opposite tail bends of a forward swim, with extensions of the outside pectoral fin in each case. The larva pauses in panel D. Panel E shows the unilateral tail bend typical of a J-turn, with the outside pectoral fin extended. An S-bend is seen in panel F, which leads to the capture of the paramecium in panel G. Strong abductions of both pectoral fins are seen immediately after capture (Panel H), before the larva turns and swims away (Panel I). Time stamps are shown for each panel. The scale bar in B represents 1 mm. The larva shown is 7 dpf.
Figure 5.
Pectoral fin movements in prey tracking.
Panel A shows the kinematics of a larva swimming toward a paramecium. The forward swim takes the form of shallow, roughly symmetrical tail bends, with extension of the outside pectoral fin. This results in alternating extensions of the fins. The distance to the paramecium decreases as a result of this maneuver. A J-turn is represented in Panel B. The tail bends in a single direction (left, or negative, in this case), and the pectoral fins beat in unison. The bearing to the prey drops, but the distance to the prey remains unchanged. There is a strong relationship between the degree of the tail bend and the size of the bearing change (Panel C, p<0.001 (unpaired t-test with Welch's correction), linear regression R2 = 0.78), while the activities of the fins have no direct effect on the magnitude of the turn (Panel D, p>0.05 in all cases, unpaired t-test with Welch's correction).
Figure 6.
Pectoral fin abduction scales with strike velocity.
Panels A, B and C show the movements of the tail and both pectoral fins for strikes of increasing velocity. The velocity of the larva is shown in blue. The moment of capture (t = 0) is indicated by a vertical dotted line. Panel D shows the correlation that exists between strike velocity and the total fin adduction that occurs following the strike (n = 8; unpaired t-test with Welch's correction, p<0.001; linear regression, R2 = 0.70). The events shown in panels A, B, and C are indicated.