The comparative hydrodynamics of rapid rotation by predatory appendages.
Countless aquatic animals rotate appendages through the water, yet fluid forces are typically modeled with translational motion. To elucidate the hydrodynamics of rotation, we analyzed the raptorial appendages of mantis shrimp (Stomatopoda) using a combination of flume experiments, mathematical modeling and phylogenetic comparative analyses. We found that computationally efficient blade-element models offered an accurate first-order approximation of drag, when compared with a more elaborate computational fluid-dynamic model. Taking advantage of this efficiency, we compared the hydrodynamics of the raptorial appendage in different species, including a newly measured spearing species, Coronis scolopendra The ultrafast appendages of a smasher species (Odontodactylus scyllarus) were an order of magnitude smaller, yet experienced values of drag-induced torque similar to those of a spearing species (Lysiosquillina maculata). The dactyl, a stabbing segment that can be opened at the distal end of the appendage, generated substantial additional drag in the smasher, but not in the spearer, which uses the segment to capture evasive prey. Phylogenetic comparative analyses revealed that larger mantis shrimp species strike more slowly, regardless of whether they smash or spear their prey. In summary, drag was minimally affected by shape, whereas size, speed and dactyl orientation dominated and differentiated the hydrodynamic forces across species and sizes. This study demonstrates the utility of simple mathematical modeling for comparative analyses and illustrates the multi-faceted consequences of drag during the evolutionary diversification of rotating appendages.
Department of Ecology & Evolutionary Biology, 321 Steinhaus Hall, University of California, Irvine, Irvine, CA 92697-2525, USA.
M J
MJ
McHenry
Department of Biology, Duke University, Durham, NC 27708, USA.
P S L
PS
Anderson
Department of Biology, Universiteit Antwerpen, Universiteitsplein 1, Antwerpen 2610, Belgium.|Département d'Ecologie et de Gestion de la Biodiversité, UMR 7179 CNRS/MNHN, 57 rue Cuvier, Case Postale 55, Paris Cedex 05 75231, France.
S
S
Van Wassenbergh
Department of Biology, University of Massachusetts Amherst, Amherst, MA 01002, USA.
D G
DG
Matthews
Friday Harbor Laboratories, University of Washington, 620 University Rd., Friday Harbor, WA 98250, USA.
A P
AP
Summers
Department of Biology, Duke University, Durham, NC 27708, USA snp2@duke.edu.
S N
0000-0001-9738-882X
SN
Patek
D000825:Animal Structures / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D033364:Decapoda / Q000033:anatomy & histology* / Q000502:physiology*; D057446:Hydrodynamics; D008954:Models, Biological; D009068:Movement; D011235:Predatory Behavior / Q000502:physiology*; D012399:Rotation; D013045:Species Specificity; D019415:Torque
Drag; Feeding; Kinematics; Phylogenetic comparative methods; Scaling; Torque