Critical Tail Autotomy for Reduction of Maximal Swimming Performance in a Plethodontid Salamander (Desmognathus quadramaculatus)
Although tail autotomy often has an immediate survival benefit, tail loss may subsequently hinder locomotion and the ability to escape from predators. Maximal locomotor performance can be reduced after tail autotomy in the plethodontid salamander Desmognathus quadramaculatus. The loss of a large proportion of the tail length (>60%) is costly for this semiaquatic species in terms of a reduction in maximal swimming performance (i.e., burst speed is about 50% less after such autotomy). However, the minimal amount of tail loss that causes a significant reduction in swimming performance (i.e., the “critical tail autotomy” for locomotion) is unknown. I examined the effect of partial tail loss (either 15% or 30% of tail length) on burst swimming performance. After the loss of about 15% of tail length in one experimental group (N = 15), burst speeds for individuals were not significantly different from preautotomy burst speeds. After the loss of about 30% of tail length in a second experimental group (N = 15), burst speeds for individuals were significantly less than preautotomy burst speeds. These results indicate that the critical tail autotomy for reduction of maximal swimming performance is between 15% and 30% of tail length. About 50% of individuals in the field (N = 69) experienced tail autotomy and most (80%) of these individuals lost more than 30% of their tails. This study shows that tail autotomy often results in a reduction in maximal swimming performance and thus a locomotor cost for individuals of this species.Abstract
Effect of tail autotomy on swimming burst speed in the salamander Desmognathus quadramaculatus. In the control group, speeds of individuals (N = 15) were measured before and after sham autotomy (i.e., no tail loss after a light grasp and release of the tail). In the 15% loss group, speeds of individuals (N = 15) were measured before and after the loss of about 15% of the tail length from autotomy. In the 30% loss group, speeds of individuals (N = 15) were measured before and after the loss of about 30% of the tail length from autotomy. Means ± SE are presented. Results from paired t-tests that compared the before and after speeds of individuals in each group are presented above bars. *P < 0.01.
Relationship between body length and tail length for individuals of Desmognathus quadramaculatus with tail loss in the field. Regression for small individuals with body length <75 mm was y = 4.603x0.538 (r2 = 0.320, F = 6.109, P = 0.028, N = 15) and regression for large individuals with body length ≥75 mm was y = 14.322x0.342 (r2 = 0.157, F = 3.347, P = 0.084, N = 20). ANCOVA demonstrated that the tails were relatively longer for large than for small individuals (F = 12.58, P = 0.001), which indicates that the amount of tail loss was less for large individuals.
