Aerial and aquatic feeding in the silver arawana, Osteoglossum bicirrhosum
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Environmental Biology of Fishes (2005) 73: 453–462 DOI 10.1007/s10641-005-3214-4
Aerial and aquatic feeding in the silver arawana, Osteoglossum bicirrhosum Dayv Lowrya, Alpa P. Wintzera,b, Michael P. Matotta,c, Lisa B. Whitenacka, Daniel R. Hubera, Mason Dean & Philip J. Mottaa a Department of Biology, University of South Florida, SCA 110, 4202 East Fowler Avenue, Tampa, FL 336205200, U.S.A b U.S. Fish and Wildlife Service, 4001 North Wilson Way, Stockton, CA 95205, U.S.A c Eckerd College, Natural Sciences Collegium, 4200 54th Avenue South, St. Petersburg, FL 33711, U.S.A. d Ecology and Evolutionary Biology, University of California Irvine, 321 Steinhaus Hall, Irvine, CA 92697, U.S.A Received 12 November 2004
Accepted 7 February 2005
Key words: leaping, kinematics, Osteoglossomorpha, feeding behaviour, feeding ecology Synopsis The silver arawana, Osteoglossum bicirrhosum, hunts along shorelines and within flooded forests in the Amazon River basin and supplements its limited consumption of aquatic vertebrates by leaping from the water to obtain terrestrial and arboreal prey. We offered O. bicirrhosum prey both suspended above and submerged below the surface of the water. From high-speed digital recordings, we measured kinematic variables associated with the jaws, cranium, pectoral fins, and body during orientation and prey capture. Aquatic and aerial feeding events were kinematically distinct, with aerial events generally involving faster, larger movements and a distinct delay in the onset of lower jaw depression until the head had left the water. The comparatively large gape during leaping may facilitate prey capture by overcoming variability in the apparent position of the prey due to refraction, while the delayed onset of mouth opening may serve to reduce the effects of drag. This distinctive leaping behaviour allows exploitation of the terrestrial prey base, especially during seasonal inundation of the Amazon River basin when the aquatic food base is widely dispersed.
Introduction Studies of prey capture in lower vertebrates typically focus on organisms that feed exclusively in either aquatic or terrestrial environments throughout their lives. Many organisms, however, exploit prey in both aquatic and terrestrial environments. Such versatility in feeding behaviour can exist concomitantly with discrete metamorphic stages (Gans & Gorniak 1982, Nishikawa & Cannatella 1991, Reilly 1996), or within a single life-history stage (Summers et al. 1998, Deban & Marks 2002, Luiselli et al. 2002). Few kinematic and behavioural studies have focused specifically
on fishes that feed in both aquatic and aerial environments during the same life history stage (Hyatt 1971, Zahl et al. 1977, Seghers 1978, Sponder & Lauder 1981). The employment of a feeding repertoire that exploits disparate prey bases can expand an organismÕs ecological niche, potentially granting a competitive advantage in nutrient acquisition capacity. Exploitation of non-aquatic food items by fishes has been documented in species that knock prey items into the water
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