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First published online April 18, 2008
Journal of Experimental Biology 211, 1386-1393 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.014688

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The effects of acute temperature change on swimming performance in bluegill sunfish Lepomis macrochirus

Emily A. Jones, Arianne S. Jong and David J. Ellerby^*

Department of Biological Sciences, Wellesley College, 106 Central Street, Wellesley, MA 02481, USA

^* Author for correspondence (e-mail: dellerby{at}wellesley.edu)

Accepted 26 February 2008

Many fish change gait within their aerobically supported range of swimming speeds. The effects of acute temperature change on this type of locomotor behavior are poorly understood. Bluegill sunfish swim in the labriform mode at low speeds and switch to undulatory swimming as their swimming speed increases. Maximum aerobic swimming speed (U_max), labriform-undulatory gait transition speed (U_trans) and the relationships between fin beat frequency and speed were measured at 14, 18, 22, 26 and 30°C in bluegill acclimated to 22°C. At temperatures below the acclimation temperature (T_a), U_max, U_trans and the caudal and pectoral fin beat frequencies at these speeds were reduced relative to the acclimation level. At temperatures above T_a there was no change in these variables relative to the acclimation level. Supplementation of oxygen levels at 30°C had no effect on swimming performance. The mechanical power output of the abductor superficialis, a pectoral fin abductor muscle, was measured in vitro at the same temperatures used for the swimming experiments. At and below T_a, maximal power output was produced at a cycle frequency approximately matching the in vivo pectoral fin beat frequency. At temperatures above T_a muscle power output and cycle frequency could be increased above the in vivo levels at U_trans. Our data suggest that the factors triggering the labriform–undulatory gait transition change with temperature. Muscle mechanical performance limited labriform swimming speed at T_a and below, but other mechanical or energetic factors limited labriform swimming speed at temperatures above T_a.

Key words: gait transition, muscle mechanics, swimming, temperature