First published online August 22, 2008
Journal of Experimental Biology 211, 2849-2858 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.016394
Antennule morphology and flicking kinematics facilitate odor sampling by the spiny lobster, Panulirus argus
Matthew A. Reidenbach*,
Nicole George and
M. A. R. Koehl
Department of Integrative Biology, University of California, Berkeley, CA
94720-3140, USA
View larger version (104K):
[in this window]
[in a new window]
|
Fig. 1. (A) Face-on view of a spiny lobster, Panulirus argus. The arrows
point to the lateral flagellum of the antennule bearing rows of aesthetascs.
(B) Scanning electron micrograph (SEM) of a three-quarter view of a P.
argus antennule, showing (1) aesthetascs, (2) mechanosensory hairs and
(3) guard hairs. The guard hairs on the left side of the image were removed to
show the zig-zag pattern of the tips of the aesthetascs. The aesthetascs and
guard hairs line the ventral side of the lateral flagellum. (C) Side view SEM
of a lateral flagellum of an antennule. (SEM photos by J. A. Goldman.)
|
|
View larger version (63K):
[in this window]
[in a new window]
|
Fig. 2. (A) Side view of video images of the downstroke flick (lasting 100 ms) by
the lateral flagellum of a P. argus antennule, showing its position
at the start (1) and end (2) of the flick as it passes through an odor plume.
The lateral flagellum of the antennule appears light because it was flicking
in a plane illuminated by a sheet of laser light. The medial flagellum of the
antennule, which did not move during the flick, appears black because it was
not in the plane illuminated by the laser. The lobster was facing upstream in
a flume (flow from left to right) and the antennule was flicking in a
turbulent plume of odor mixed with fluorescent dye (fluorescein), which
appears as pale filaments swirling in the water around the antennule. (B)
Diagram of a cross-section of the lateral flagellum, showing the orientation
(angle between dotted lines) of the aesthetascs with respect to the direction
of the rapid antennule downwards flick (left diagram) and slower upwards
return stroke (right diagram). The direction of water motion relative to the
antennule, which changes as a result of the antennular motion is indicated by
the solid arrows.
|
|
View larger version (111K):
[in this window]
[in a new window]
|
Fig. 3. (A) Ventral and (B) side views of the scaled model (40:1) of the midsection
of the lateral flagellum of the antennule of a P. argus. The distal
end of the antennule is to the left, and proximal end is to the right in the
image. The guard hairs and aesthetascs were made from Pyrex© glass to
match the index of refraction of mineral oil used as the viscous fluid in the
towing tank. The lateral flagellum of the antennule to which the hairs were
attached was fabricated using Sculpy© modeling compound.
|
|
View larger version (33K):
[in this window]
[in a new window]
|
Fig. 4. Schematic diagram of towing-tank. The model of the antennule was attached
to a computer-controlled motorized rail table (Daedal MC6023) positioned over
the top of the tank and towed through the mineral oil. Neutrally buoyant
marker particles (Potter Industries© 11 µm silver-coated hollow glass
spheres) in the mineral oil were illuminated by a sheet of laser light and
imaged using a Redlake Motionscope PCI 1000s video camera at 60 frames per
second. The camera was mounted directly above the tank on the same towing rig
as the model, and thus captured images of the particle motion relative to the
model. The model was towed in both a horizontal (as shown) and vertical
orientation. Towing the model from right to left simulates an antennule in the
`downward' flicking orientation, while a slower tow from left to right
simulates an antennule in the `upstroke' return orientation.
|
|
View larger version (56K):
[in this window]
[in a new window]
|
Fig. 5. PIV measurements of water velocities relative to a dynamically scaled model
of the midsection of the lateral flagellum of the antennule of a P.
argus during (A) the downward (to the left) flick and (B) the upward (to
the right) return stroke. Black arrows indicate direction of antennule motion.
Small yellow arrows in the fluid represent the water velocity vectors relative
to the antennule lateral flagellum. The model operated at the same Re
as the real antennule, and the velocities shown here have been converted to
the velocities that would occur relative to the real lobster antennule, which
flicks downward at 9 cm s–1 and returns upward at 2.0 cm
s–1. Background color indicates velocity magnitude.
Velocities were computed as the average of 90 measurements at each location.
The locations of the guard hairs are shown by wide white curves, and of the
aesthetascs by a box outlined with a narrow white line. In A, location 1 is
referred to as the ventral side of the hair array, and location 2 is referred
to the dorsal side of the hair array.
|
|
View larger version (60K):
[in this window]
[in a new window]
|
Fig. 6. Magnified view of PIV velocity measurements relative to the aesthetasc
array during a flick downstroke (details described in
Fig. 5). Flick direction is
from right to left. The velocity transects shown in
Fig. 7 were taken along the
mid-line of the aesthetasc array (highlighted in red). The surrounding white
box indicates the location of the aesthetasc hair array.
|
|
View larger version (30K):
[in this window]
[in a new window]
|
Fig. 7. (A) Side and (B) ventral view of a model of the midsection of the lateral
flagellum of a P. argus antennule, which has been painted black so
that the zig-zag arrangement of the aesthetascs can be easily seen. Lines
labeled 1–3 indicate three locations where velocity transects were taken
at right angles to the surface of the antennule flagellum, with corresponding
velocity measurements shown in graph in C. In total, 20 transects were made at
different locations through the aesthetasc array. All distances and velocities
have been converted to those for a real antennule. A distance of 0 mm
corresponds to the base of the aesthetascs next to the lateral flagellum of
the antennule; 0.8 mm corresponds to the tips of the aesthetascs. High flow
occurs both near the tips of the aesthetascs and at specific locations within
the array where gaps in the zig-zag hair arrangement occur.
|
|
View larger version (5K):
[in this window]
[in a new window]
|
Fig. 8. Mean velocity of fluid within the aesthetasc hair array as a function of
Reynolds number (calculated using aesthetasc diameter; L). The
natural flick occurs at a Re=2. Twenty velocity transects were
obtained at different locations within the aesthetasc array (as shown in
Fig. 7). Mean velocity was
computed as the area-averaged velocity along the mid-line of the 20 transects.
Error bars indicate one standard deviation.
|
|
View larger version (37K):
[in this window]
[in a new window]
|
Fig. 9. (A) PIV measurements of water velocities relative to the aesthetascs of a
dynamically scaled model of the lateral flagellum of the antennule of a P.
argus during a flick downstroke (from right to left, details described in
Fig. 5). The aesthetascs in
this case point in the same direction as antennule motion, rather than being
oriented 32° from the direction of the oncoming flow relative to the
antennule (see Fig. 2). (B)
Peak velocity along the mid-line of the aesthetasc array (transect shown in
red) and the mean velocity. Mean velocity was computed as the area-averaged
velocity for the 20 transects made through the array. Peak velocity was the
maximum velocity measured at a given distance from the lateral flagellum along
any of the transects.
|
|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
© The Company of Biologists Ltd 2008
