Two sniffing strategies in palinurid lobsters
J. A. Goldman* and
S. N. Patek
Biology Department, Duke University, Durham, NC 27708, USA
* Present address: American Institute of Biological Sciences, 1444 Eye Street,
NW, Suite 200, Washington, DC 20005, USA
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Fig. 1. The antennules and flagella of Palinurus elephas. (A) An anterior
view of P. elephas (carapace length 138 mm) showing the location of
the antennae (ant) and antennules. The antennules are composed of antennular
peduncles with three segments (p1, p2 and p3) and antennular flagella (af).
Scale bar, 26 mm. (B) The antennular flagella with the medial flagellum (mf)
towards the top of the figure and the lateral flagellum (lf) below. Note the
discrete aesthetasc tuft (at; length 8 mm) on the lateral flagellum. Scale
bar, 1.7 mm. (C) An orthogonal view of the diffuse array of aesthetasc tips
with the guard hairs removed.
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Fig. 2. Illustration of the video analysis technique used for tracking antennule
movement. (A) Video images of a flicking right antennule show the motion of
the lateral flagellum (lf) during the closing phase; the medial flagellum (mf)
remains stationary. The location of the antennule edge was determined by
superimposing a line tangent (tl) to the motion of the arc swept by the
lateral flagellum. To clearly show the lateral flagellum's motion, this
illustration presents images and tangent lines at the start (tl0)
and end (tl1) of a 22 ms time period (images were actually sampled
every 2 ms). Scale bar, 4.9 mm. (B) The pixel intensity profile from the
tangent line (tl) was used to locate the lateral flagellum's edge and to
calculate position and speed during a flick. For illustration purposes, we
show a small number of pixels with an intensity profile including only white
(background) or dark stippling (flagellum) rather than the hundreds of pixels
and continuous shades of gray actually used in the analyses. Times
tl0 and tl1 correspond to the tangent lines denoted as
tl0 and tl1 in panel A. Arrows indicate the moving edge
of the lateral flagellum.
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Fig. 3. Scanning electron micrographs of the setae found on the lateral and medial
flagella of Palinurus elephas. The lateral flagellum (A-D) has an
aesthetasc tuft, which is flicked through the water. The medial flagellum
(E-F) remains stationary during the flick. Distal is towards the left of the
page in images A-E. (A) The lateral region of the aesthetasc tuft shows the
aesthetascs (ae), which form paired rows on each annulus (an) of the
flagellum. A single guard hair (g) per annulus flanks both medial and lateral
edges of the aesthetasc tuft. Paired simple companion hairs (sc) only are
located on the lateral side of the aesthetasc tuft. Scale bar, 0.5 mm. (B)
Paired plumose companion hairs (pc) are found only on the medial region of the
aesthetasc tuft. Scale bar, 0.5 mm. (C) The ventro-lateral side of the lateral
flagellum shows the positions of setae along the aesthetasc tuft. The
asymmetric setae (as) are found on the lateral side of the aesthetasc tuft
just proximal to the guard hairs (g). Scale bar, 0.5 mm. (D) The lateral
region of the aesthetasc tuft is shown with guard hairs and companion hairs
removed so that the paired arrangement of aesthetasc rows per annulus is
visible. Scale bar, 0.5 mm. (E) Long plumose setae extend along the medial
flagellum. Scale bar, 0.5 mm. (F) Each plumose hair on the medial flagellum
has an array of setules extending along its axis. Scale bar, 0.01 mm.
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Fig. 4. A cross-sectional view of the antennule flagella and setae during a flick.
The lateral flagellum is rapidly flicked ventrally during the closing phase
(towards the bottom of the figure) and opened more slowly. Aesthetascs are
aligned such that fluid flows between rows. The medial flagellum is not
actively moved and its plumose setae remain slightly below the lateral
flagellum during the flicks. The location of the medial flagellum's simple
setae shifts medio-laterally along the length of the flagellum.
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Fig. 6. Comparisons of lateral flagellum length (A) and peduncle length (B) for a
given body size (carapace length) across lobster species. Circles represent
individuals from the Panulirus genus. Squares represent members of
the Palinuridae other than Panulirus. Triangles represent members of
the Scyllaridae and Nephropidae.
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Fig. 7. Kinematic chronology of four representative flicks produced by a
Palinurus elephas individual. (A) The lateral flagellum is shown at
the starting position (arbitrarily set as zero) in which it is opened at a
maximum distance from the medial flagellum. Then, the flagellum rapidly closes
(red bracket) and slowly opens (blue bracket) four times. (B) The closing
phase (red bracket, negative speed values) is faster and of shorter duration
than the opening phase (blue bracket, positive speed values) of each
flick.
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Fig. 8. Sampled water area ( ) varies dramatically with small increments in
lateral flagellum length. Panulirus species (circles) sample orders
of magnitude larger water area per one degree of a closing phase than do other
palinurid species (squares) and nephropid and scyllarid lobsters
(triangles).
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© The Company of Biologists Ltd 2002
