Costs Of Tail Autotomy Research Articles

Effect of temperature, photoperiod, and feeding on the rate of tail regeneration in a semiaquatic plethodontid salamander

Salamander tail autotomy improves survival, but loss of the tail can subsequently be costly. For example, burst swimming speed is significantly slower after autotomy in desmognathan salamanders, which may increase predation risk in aquatic habitats. However, any long-term cost of tail loss is contingent on the rate of tail regeneration. To examine variation among seasons and environments in the cost of tail autotomy, we tested the effect of temperature, photoperiod, and feeding on tail-length re-growth in the semiaquatic plethodontid salamander Desmognathus conanti. Eight experimental groups (n=15 each, equivalent in body size) were tested. After acclimation for four weeks at one of two temperatures (either 10°C or 20°C) and one of two photoperiods (either L:D 9.5:14.5h or 14.5:9.5h), 60% of the tail length was autotomized for each individual. After autotomy, each experimental group was maintained under unique conditions of temperature (either 10°C or 20°C), photoperiod (either L:D 9.5:14.5h or 14.5:9.5h), and feeding (either fasting or weekly feeding). The length of the regenerated tail portion for each individual was measured each week until the group with the fastest re-growth had regenerated 50% of the lost tail length. Low temperature had a large, negative effect, fasting had a small, negative effect, but photoperiod had no significant effect on tail re-growth. The large thermal effect resulted from a combination of delayed initiation of tail-length re-growth and reduced regeneration rate thereafter at low temperature. We conclude that the cost of salamander tail autotomy differs among seasons and environments based on variation in temperature and food availability.

Sex, Reproductive Status, and Cost of Tail Autotomy via Decreased Running Speed in Lizards

AbstractAutotomy, voluntary shedding of body parts to permit escape, is a theoretically interesting defense because escape benefit is offset by numerous costs, including impaired future escape ability. Reduced sprint speed is a major escape cost in some lizards. We predicted that tail loss causes decreased speed in males and previtellogenic females, but not vitellogenic females already slowed by mass gain. In the striped plateau lizard, Sceloporus virgatus, adults of both sexes are subject to autotomy, and females undergo large increases in body condition (mass/length) during vitellogenesis. Time required for running 1 m was similar in intact autotomized males and previtellogenic females, but increased by nearly half after autotomy. Vitellogenic females were slower than other lizards when intact, but their speed was unaffected by autotomy. Following autotomy, speeds of all groups were similar. Thus, speed costs of autotomy vary with sex and reproductive condition: decreased running speed is not a cost of autotomy in vitellogenic females or presumably gravid females. Costs of autotomy are more complex than previously known. Speed and other costs might interact in unforseen ways, making it difficult to predict whether strategies to compensate for diminished escape ability differ with reproductive condition in females.

Some vaguely explored (but not trivial) costs of tail autotomy in lizards

Lizard tail autotomy is considered an efficient anti-predator strategy that allows animals to escape from a predator attack. However, since the tail also is involved in many alternative functions, tailless animals must cope with several costs following autotomy. Here we explicitly evaluate the consequences of tail autotomy for two costs that have been virtually unexplored: 1. we test whether the anatomical change that occurs after tail loss causes a reduction in the role of the tail as a distraction mechanism to predators; 2. we analyzed whether tail synthesis comprises an energetically costly process in itself, by directly comparing the cost of maintenance before and after autotomy. We found that original tails displace further and at greater velocity than regenerated tails, indicating that the anti-predation responses of a lizard probably changes according to whether its tail is original or regenerated. With regard to the energetic cost of tail synthesis, we observed a significant increase in the standard metabolic rate, which rose 36% in relation to the value recorded prior to tail loss. This result suggests that the energetic cost of tail synthesis itself could be enough to affect lizard fitness.

Inter‐populational variation in the cost of autotomy in the metallic skink (Niveoscincus metallicus)

AbstractMany species of lizard use tail autotomy to escape from potential predators. While frequency of tail loss is an unreliable indicator of predation intensity it may enable inter‐populational comparisons of predation costs. This reasoning was applied to a study of the metallic skink Niveoscincus metallicus. A total of 368 lizards was sampled from across four populations to compare the frequency and position of tail loss and ultimately to examine whether the implications of tail autotomy differ between populations. The overall frequency of tail loss was 72%, although between populations the incidence of tail autotomy varied from 61.4% (Laughing Jack Lagoon) to 78.2% (Dynnyrne). No sexual differences were observed in the frequency of tail loss; however, the incidence of autotomy increased with age. The estimated position of tail loss did not vary between the sexes, although individuals from Dynnyrne experienced more proximal tail breaks than the other populations. This resulted in the predicted energetic cost of tail loss being significantly higher in the Dynnyrne population and, when combined with a high frequency of tail loss and relatively smaller body size, suggests that this population incurs relatively high costs as a result of autotomy. Overall, measures of tail loss in N. metallicus were found to be useful for examining inter‐populational variation in the cost of tail autotomy.

Costs associated with tail autotomy in an ambush foraging lizard, Cordylus melanotus melanotus

Tail autotomy is a widespread method of escape among lizards and can be costly. Most studies on the effects of tail loss have focused on active foraging lizards, but few data exist for ambush foraging lizards. We investigated potential costsassociated with tail autotomy in an extreme ambush foraging cordylid lizard, Cordylus melanotus melanotus. We induced tail autotomy in free ranging male Cordylus m. melanotus and measured potential shifts in behaviour (movements, foraging behaviour, time exposed and average distance to a potential refuge), and responses to an approaching human compared to marked individuals with complete tails. Tailed and tailless lizards behaved in a similar fashionfor all measured variables although power tests could not rule out the possibility of falsely accepting the null hypothesis in some cases. We also measured locomotory performance (maximum sprint speed) for tailed and tailless lizards in the lab. Locomotory performance was also not compromised by tail loss. Finally, we measured the energetic content of tails as a proportion of total energetic content using bomb calorimetry. The cost of tail autotomy was approximately 12 % of the totalbody energy (wet weight). Our results suggest that the major cost of tail loss in Cordylus m. melanotus is energetic.

Sexual Dimorphism in the Ease of Tail Autotomy: Uta stansburiana with and without Previous Tail Loss

relative costs and benefits. The same may be true for the development of tail autotomy in the two sexes of the same species. We examined the ease of tail autotomy of male and female Uta stansburiana. Correcting for tail thickness, males lose their tail significantly less easily than females and retain it even more strongly as they grow larger from sexual maturity on. Although both sexes lose social status after tail loss, females may have available an alternative, subordinate, social role in which they can retain some reproductive success. Males do not have such an alternative strategy, and since they need both a complete tail and high social status for reproductive success, they require more stimulus to autotomize their tail (i.e., the cost of tail autotomy is higher in males than in females). For both males and females, lizards with incomplete tails from a previous autotomy have reduced antipredator defense via tail autotomy. We predicted that second-time autotomy would occur more readily, as compensation. But females did not show this compensation and autotomized the tail with equal ease the first and second times. Males autotomized more easily the second time, but we do not interpret this change as compensation for a shorter tail. For males, the cost of tail loss is much reduced after a prior tail autotomy; they have already lost their social status following autotomy, and further tail loss is less consequential. At the second autotomy, males reduced their ease of tail autotomy to equal that of females, and females did not show facilitated second-time autotomy. Therefore, males, like females, did not show easier tail autotomy as compensation for an incomplete tail.

Lack of respiratory “cost” of tail autotomy in the lungless salamander, Oedipina uniformis

Tail autotomy, an effective antipredator adaptation that enhances survival, may have attendant costs for the surviving prey. One potential cost not previously addressed in long-tailed, lungless salamanders that sacrifice the majority of their body mass by tail autotomy is the substantial reduction in respiratory surface area (RSA). We have tested the respiratory cost of tail autotomy in the bolitoglossine salamander, Oedipina uniformis, by (1) comparing resting and post-exercise oxygen consumption (VO2) in tailed and tailless Oedipina, and (2) comparing the tissue composition of bodies and tails. Metabolic studies indicated no significant effect of tail condition (pre- vs. post-autotomy) on resting VO2, the duration of exercise prior to exhaustion, or post-exercise VO2; aerobic recovery from exercise was also independent of tail condition. Tissue analyses (water and ash content, carbohydrate, lipid, and protein fractions) revealed that Oedipina bodies and tails are similar in composition (both high in muscle, low in lipid); thus the tail is largely a metabolically-homogeneous extension of the body. Our data suggest that tail autotomy in Oedipina does not alter the ratio between metabolically-active tissue mass and RSA, and that a respiratory cost of tail autotomy is of minor importance.