Effect of ontogenetic increases in body size on burst swimming performancein tadpoles of the striped marsh frog, Limnodynastes peronii

The effect of ontogenetic increases in total length on burst swimming perfo rmance was investigated in tadpoles of the striped marsh frog (Limnodynaste s peronii) over the total-length range of 1.5-4 cm and Gosner developmental stages 25-38. The burst swimming performance of tadpoles at 10 degrees and 24 degrees C was determined by videotaping startle responses with a highsp eed video camera at 200 Hz and analysing the sequences frame by frame. Maxi mum swimming velocity (U-max) and acceleration (A(max)) increased with tota l length (L) at a rate that was proportionally greater than the increase in total length (i.e., positive allometry; exponents >1) and was described by the allometric equations U-max = 0.061L(1.34) and A(max) =1.15L(1.11) at 1 0 degrees C and U-max = 0.114L(1.34) and A(max) = 1.54L(1.11) at 24 degrees C. Stride length increased with a total-length exponent of approximately 1 bur was unaffected by temperature. Tail-beat frequency was not affected by total length and increased from 7.8 +/- 0.2 Hz at 10 degrees C to 21.7 +/- 0.7 Hz at 24 degrees C. Developmental stage did not significantly influenc e the relationship between total length and U-max or A(max). Furthermore, t emperature and the associated changes in water viscosity did not affect the relationship between total length and burst swimming performance. At their U-max, Reynolds numbers ranged from approximately 1,500 in the smaller tad poles up to 50,000 for the larger animals at 24 degrees C We suggest the po sitive allometry of U-max in larval L. peronii was due in part to the incre ases in tail width (TW) with total length (TW= -1.36(1.66)), possibly refle cting the increasing importance of burst swimming performance to survival d uring larval development.