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First published online November 19, 2007
Journal of Experimental Biology 210, 4083-4091 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.008664

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The flow generated by an active olfactory system of the red swamp crayfish

P. Denissenko^1,*, S. Lukaschuk¹ and T. Breithaupt²

¹ Fluid Dynamics Laboratory, University of Hull, HU6 7RX, UK
² Department of Biology, University of Hull, HU6 7RX, UK

View larger version (21K): [in this window] [in a new window]   Fig. 1. (A) Location of fan organs and major chemoreceptors (antennules) of crayfish. The fan organs are multisegmental flagellae (exopodites) of the mouthparts (maxillipeds) and are feathered distally (B). (B,C) Scanning electron micrographs taken during the power stroke (B), showing the extended feathered hairs. During the recovery stroke (C) the feathered hairs are folded in. Scale bars, 1 mm. Reprinted from Breithaupt (Breithaupt, 2001) with permission of The Biological Bulletin.

View larger version (23K): [in this window] [in a new window]   Fig. 2. Experimental setup. A crayfish is suspended above the treadmill (TM). A lasersheet is generated by a laser (L). A PIV camera is set to the position C1 (C2) and the lasersheet is aligned along the plane LS1 (LS2) to measure the two components of velocity field in horizontal (vertical) planes (blue broken boxes). A video camera (VC) is used to monitor the crayfish fanning activity.

View larger version (62K): [in this window] [in a new window]   Fig. 3. Ink visualization of the jets generated by the crayfish fan organs. Bilateral jets directed at 25° and 40° upwards (A) and horizontally (B); unilateral jet directed horizontally (C). Water-based ink for a fountain pen was used. After the animal had been observed fanning for about 1 min, the ink was slowly released from a pipe of 0.6 mm i.d. placed in front of the animal fan organs. Caution was taken to prevent the ink from getting in contact with the animal's chemoreceptors. The photo in A was acquired 5 s, and in B and C, 30 s, after the beginning of the ink injection.

View larger version (11K): [in this window] [in a new window]   Fig. 4. The flow generated by crayfish fan organs consists of the jets and the inflow (A). The inflow converges towards the jets' origin and towards jets' axes. At a distance larger than the jets' length the flow is virtually unaffected by a crayfish fanning activity. The jets are generally out of horizontal plane, so the sketch shows a projection. To mimic the flow created by a crayfish, an assembly of an inlet and two outlet nozzles (B) was designed. The water was pumped through a closed loop providing fluid conservation, which is obviously the case for a crayfish.

View larger version (40K): [in this window] [in a new window]   Fig. 5. Right, the flow field measured at the crayfish plane of symmetry (vertical laser sheet LS2 in Fig. 2) averaged over 30 instantaneous measurements (30 s). The fluid converges towards the fan organs in the plane of measurements and escapes in the form of jets in a perpendicular direction (not shown). Reference segment at the bottom, 2 cm; reference vector, 1 cm s–1. The negative image of the crayfish cut from a PIV image is shown for reference. The broken line indicates the contour of the blindfold which is shaded from the laser sheet and thus is not visible in the image. The animal's appendages are denoted on the left; LR1A, lateral right antennule; R2A, right second antenna; L2A, left second antenna; MR1A, medial right antennule; LL1A, lateral left antennule; ML1A, medial left antennule; FO1, FO2, FO3, extended exopodite of fan organs 1 to 3; RM, LM, endopodite of right and left third maxilliped. Note that lateral antennules LR1A and LL1A are lowered in front of the fan organs, exposing chemoreceptors to the inflow.

View larger version (77K): [in this window] [in a new window]   Fig. 6. Examples of the velocity field generated by a crayfish measured in a horizontal plane LS1 (Fig. 2). (A) The instantaneous velocity field (B–D) averages over 30 instantaneous measurements taken at 1 s time intervals. Velocity field A is one of those used to obtain the field C. Fields A–C were recorded from a female animal; the field D was recorded from a male. The fluid converged towards the animal head region, escaping within the jets located outside the plane of measurement. Negative images of the animal cut from a PIV image are shown for a reference. Reference segments at the bottom left, 2 cm; reference vector, 1 cm s–1. The jets created by the animal are outside the plane of measurement and thus are not observed in the vector field. Profiles of the horizontal fluid velocity along the enumerated streamlines (broken lines) are correspondingly plotted in Fig. 8A–D.

View larger version (74K): [in this window] [in a new window]   Fig. 7. Velocity field generated by the mechanical model (Fig. 4B) measured in a horizontal plane LS1 (Fig. 2). Negative images of the device cut from a PIV image are shown for a reference. The positions of the jets produced by a model are indicated by bold red arrows. Two jets directed to the sides (C), 45° backwards (A), 45° upwards, off the plane of measurement (B), a single jet directed to the left (D). Reference segment at the bottom left, 2 cm; reference vector, 1 cm s–1. Short arrows at jet locations and over the model correspond to the `noise' of image processing software and are not indicating any real values of fluid velocity. Profiles of the horizontal fluid velocity along the enumerated streamlines (broken lines) are correspondingly plotted in Fig. 9A–D.

View larger version (23K): [in this window] [in a new window]   Fig. 8. Absolute value of fluid velocity plotted vs distance from the crayfish fan organs along the corresponding enumerated streamlines in Fig. 6A–D. Broken lines correspond to the velocity inversely proportional to the distance, as in Eqn 1.

View larger version (22K): [in this window] [in a new window]   Fig. 9. Absolute value of fluid velocity vs distance from the jets origin along the enumerated streamlines corresponding to those in Fig. 7A–D. Broken lines correspond to the velocity inversely proportional to the distance, as in Eqn 1.