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Litoria Nasuta ) Author(S): Rob S Division of Comparative Physiology and Biochemistry, Society for Integrative and Comparative Biology Explosive Jumping: Extreme Morphological and Physiological Specializations of Australian Rocket Frogs ( Litoria nasuta ) Author(s): Rob S. James and Robbie S. Wilson Source: Physiological and Biochemical Zoology, Vol. 81, No. 2 (March/April 2008), pp. 176-185 Published by: The University of Chicago Press. Sponsored by the Division of Comparative Physiology and Biochemistry, Society for Integrative and Comparative Biology Stable URL: http://www.jstor.org/stable/10.1086/525290 . Accessed: 04/11/2015 22:42 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press and Division of Comparative Physiology and Biochemistry, Society for Integrative and Comparative Biology are collaborating with JSTOR to digitize, preserve and extend access to Physiological and Biochemical Zoology. http://www.jstor.org This content downloaded from 23.235.32.0 on Wed, 4 Nov 2015 22:42:16 PM All use subject to JSTOR Terms and Conditions 176 Explosive Jumping: Extreme Morphological and Physiological Specializations of Australian Rocket Frogs (Litoria nasuta) Rob S. James1,* chanics, and locomotor performance (Marsh 1994; Rome 2002; Robbie S. Wilson2,† Toro et al. 2003; James et al. 2005, 2007). The relative simplicity 1Department of Biomolecular and Sport Sciences, Faculty of of this locomotor system allows ballistics formulas to be used Health and Life Sciences, Coventry University, Coventry CV1 to calculate kinematic and kinetic variables of jump perfor- 5FB, United Kingdom; 2School of Integrative Biology, mance and to highlight the relationships between morpholog- University of Queensland, St. Lucia, Queensland 4072, ical, physiological, and kinematic variables. Jump distance can Australia be calculated from takeoff velocity and takeoff angle, variables that can be readily determined using video analysis and force Accepted 6/25/2007; Electronically Published 1/11/2008 platform data (Eq. [1]). Jump distance is also found to be dependent on morphological and physiological variables (Eq. [2]; Marsh 1994). In theory, jump distance in geometrically similar animals is independent of body size (Hill 1950). How- ABSTRACT ever, considerable variation in body form between species re- Anuran jumping is an ideal system for examining the rela- sults in variation in maximum jump distance with body size, 0.20 tionships between key morphological, physiological, and ki- typically yielding a between-species scaling exponent of Mb nematic parameters. We used the Australian rocket frog (Litoria (Marsh 1994; James et al. 2007). Anuran jumping is an ideal nasuta) as a model species to investigate extreme specialization system for examining the relationships between these variables of the vertebrate locomotor system for jumping. We measured because the contractile properties of frog hindlimb muscle have the ground reaction forces applied during maximal jumps using been extensively studied, and there is large interspecific vari- a custom-designed force platform, which allowed us to calculate ation in jump performance that appears to be related to spe- instantaneous measures of acceleration, velocity, power output, cialization in morphology (Zug 1978; Marsh 1994; James et al. and total jump distance. We quantified the mechanical prop- 2007). erties of the plantaris longus muscle using the work loop tech- nique. We found that L. nasuta achieved the second-longest v2 sin2a d p ,(1) relative jumping distance for any anuran (55.2 body lengths g for one individual) and the highest published anuran values for isolated net mean muscle power output measured using Ϫ1 where d is the horizontal displacement of the center of mass, work loops (93.5 W kg muscle mass), hindlimb length to essentially the distance jumped (e.g., m),v is takeoff velocity snout-vent length ratio (2.02), and relative hindlimb muscle (e.g., m sϪ1), a is takeoff angle, and g is the acceleration due mass (33% of body mass). Litoria nasuta also had a higher ratio to gravity (approximately 9.8 m sϪ2). of tibia length to snout-vent length than 19 related species. We found that the mean power output expended during the takeoff 2/3 W˙ # L sin2a phase of jumping in the individual that jumped the farthest d p # ,(2) ()Mg was about three times greater than our estimate of available b muscle power output. where d is the horizontal displacement of the center of mass, W˙ is the average power generated/required for the jump (the kinetic energy at takeoff divided by the time required to attain Introduction this energy), L is distance from the center of mass to the tip of the toes, and Mb is body mass of the animal (Marsh 1994). Jumping performance is commonly used as a model to inves- Equation (2) suggests that any species capable of extreme tigate relationships between morphology, skeletal muscle me- jumping performance probably exhibits a number of morpho- logical and/or physiological adaptations (Emerson 1985; James * E-mail: [email protected]. et al. 2007), such as increasing relative hindlimb length (to †E-mail: [email protected]. increase L and/or L : Mb ratio), increasing the proportion of Physiological and Biochemical Zoology 81(2):176–185. 2008. ᭧ 2008 by The body mass devoted to skeletal muscle mass used to power jump- ˙˙ University of Chicago. All rights reserved. 1522-2152/2008/8102-07030$15.00 ing (to increaseWW and/or : Mb ratio), altering muscle me- DOI: 10.1086/525290 chanics to increase muscle power output (to increaseW˙ ), and This content downloaded from 23.235.32.0 on Wed, 4 Nov 2015 22:42:16 PM All use subject to JSTOR Terms and Conditions Specializations for Extreme Frog Jumping Performance 177 increasing elastic strain energy used to enhance muscle power using a force platform to determine acceleration, takeoff ve- output (to increaseW˙ ). Both relative hindlimb length (hind- locity, and jump distance; calculate total power output used in limb length : body length) and relative hindlimb muscle mass the jump; determine the muscle mechanics of one of the pri- (muscle mass : body mass) have been found to vary among mary jumping muscles; analyze gross morphology and amount species and to affect jump performance. Frog (Emerson 1978) of muscle devoted to jumping; estimate the likely contribution and mammal species (Emerson 1985) that are jump specialists of elastic potential energy to jumping performance; compare have relatively longer legs. Also, frog (Rand 1952; Zug 1972; measurements made on this extreme specialist to those made Choi and Park 1996; Choi et al. 2003) and lizard species (Losos previously on other anurans. The likely mechanisms involved 1990; Toro et al. 2003) with relatively longer hindlimbs have in the extreme jumping performance of the rocket frog will generally been found to achieve greater jump distance and/or then be evaluated using an appropriate anuran phylogeny where takeoff velocity. Hindlimb muscle mass in frogs (Emerson 1978) possible. and mammals (Alexander et al. 1981) varies as a proportion of body mass, with jumping species having proportionally Material and Methods larger extensor muscles than nonjumping species. In addition, Animals anurans with relatively greater thigh muscle mass have been found to achieve relatively higher jump takeoff velocity (ex- Fourteen calling male Australian striped rocket frogs (Litoria pressed relative to body mass; Choi et al. 2003). nasuta Gray, 1842) were collected in the areas surrounding The total power available for a jump may also be improved Brisbane, Australia. All frogs were immediately returned to the by modifications in muscle contractile dynamics. It seems likely University of Queensland and maintained in30 # 30 # 30 -cm that during maximal jumping performance extensor muscles aquariums containing freshwater and several shelters. Jumping are maximally activated while shortening at an optimal velocity performance of frogs was recorded within 24 h of capture, while and while working over a range of sarcomere lengths for op- muscle mechanics experiments were performed within 5 d of timal power generation (Lutz and Rome 1994). However, the collection. All experiments were approved by the University of mechanical properties of frog skeletal muscle vary among spe- Queensland Animal Ethics and Experimentation Committee cies, among individuals within a species, and between muscles (SIB/821/05/UQ) and Queensland National Parks and Wildlife within an individual as a result of variation in muscle com- Permits (WISP03763706). position (Putnam and Bennett 1983; Marsh 1994). For example, there is significant variation in frog muscle fiber type propor- Jumping Performance tions between different muscles within individual Rana pipiens (Lutz et al. 1998). The muscles used to power jumping are Maximum jumping performance was determined for eight L. mainly (86%) composed of muscle fibers that contain only type nasuta between 2.7 and 8.8 g body mass at 25ЊC using a custom- 1 (the fastest and most powerful) myosin heavy chain, whereas designed force platform. The design of the force platform was in the nonjumping muscles, 29% of muscle fibers contained based on that outlined by Katz and Gosline (1993) for mea- only type 1 myosin heavy chain (Lutz et al. 1998). Therefore, suring the jumping performance of locusts, and our design and jumping performance could be maximized via an increased validation of this equipment is described in detail by Wilson percentage of fast muscle fibers resulting in higher available et al. (2000a). Ground reaction forces during takeoff were re- muscle power output. corded at a frequency of 1,000 Hz using a Powerlab data ac- The August Krogh principle states that “for many problems quisition system.
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