Performance of motor systems in Antarctic fishes

Abstract

Velocities of swimming and eye movements were measured in several species of nototheniid fish living at −1.9 °C in McMurdo Sound, Antarctica. 1. The most common mode of swimming was labriform. The speed of labriform swimming inPagothenia borchgrevinki, a cryopelagic species, was a linear function of pectoral fin beat frequency, reaching a maximum of 38 cm s−1 (1.8 L s−1) at a fin beat frequency of about 2 Hz (Fig. 2). 2. Subcarangiform swimming was employed for short dashes and escape responses. In this modeP. borchgrevinki attained a maximum swimming speed of 110 cm s−1 (4.9 L s−1) at a caudal fin beat frequency of 5.7 Hz. 3. The maximum amplitude of saccadic eye movements was about 20° inP. borchgrevinki, and 30° in the benthic speciesTrematomus bernacchii andT. centronotus. In all 3 species, amplitude was correlated with saccade velocity (Fig. 6). 4. Saccade velocities were variable compared with those of mammals. Outward saccades (away from the resting position of the eye) were slower than return saccades of the same amplitude. The maximum velocity of outward saccades was about 50 deg s−1; that of return saccades was about 120 deg s−1. 5. Maximum swimming speeds in antarctic fish are close to speeds predicted by extrapolation to the same temperature from temperate fishes, but saccade velocities are higher than predicted. The difference is attributed to a relative lack of temperature compensation in muscle, while there is a greater degree of compensation in the central nervous system.