Abstract
Tadpoles of two sympatric anurans, Bufo gargarizans Cantor, 1842 and Rana zhenhaiensis Ye, Fei & Matsui, 1995, were used as model organisms to examine the effects of different levels of tail loss on swimming performance and survival. On average, B. gargarizans tadpoles were shorter and had smaller tails and body mass than R. zhenhaiensis. After 75% tail loss, the survival rate of experimental and control B. gargarizans tadpoles, and of experimental tadpoles of the two species, differed significantly; the number of tadpoles surviving a complete impairment of their swimming ability did not differ between B. gargarizans and R. zhenhaiensis. After 50% tail loss, the swimming performance (swimming speed, maximum distance and number of stops) of the two species was significantly affected. However, the adverse influence of tail loss on the swimming speed of B. gargarizans tadpoles was greater compared to R. zhenhaiensis tadpoles. Our data indicates that a 50% tail loss results in swimming costs for B. gargarizans and R. zhenhaiensis tadpoles, and that 75% tail loss decreases the survival rate of B. gargarizans tadpoles. Therefore, we conclude that tadpoles of different species and with the same degree of tail loss use distinctive strategies to improve individual fitness in the face of predator pressure.
Highlights
The tail of anuran tadpoles is viscoelastic and fragile
The mean value for developmental stage did not differ between the E and C tadpoles, nor between the two species; the mean value for body length in B. gargarizans tadpoles was significantly smaller than in R. zhenhaiensis tadpoles; the mean values for tail length and body mass were significantly smaller in B. gargarizans tadpoles than
After accounting for body length, our results showed that intact tails of B. gargarizans tadpoles were significantly smaller than of R. zhenhaiensis tadpoles (Table I)
Summary
The tail of anuran tadpoles is viscoelastic and fragile. When a larva is grasped by an aquatic predator, its tail will stretch and tear apart (MORIN 1985, DOHERTY et al 1998). A high frequency of tail damage has been observed in natural populations of tadpoles, which indicates that B. gargarizans tadpoles can only escape from an aquatic predator if their tail is grabbed first (BLAIR & WASSERSUG 2000, DOHERTY et al 1998). It remains to be investigated whether mortality risk is really lower when the tadpole is attacked by the tail, and whether a larger tail works against the prey by calling the attention of aquatic predators (VAN BUSKIRK et al 2003). The swimming speed and maximum distance traveled by Hyla chrysoscelist tadpoles were significantly affected when more than 50% of their tail was cut off (FIGIEL & SEMLITSCH 1991)
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