Lack of functional link in the tadpole morphology induced by predators

Abstract

Most studies of predator-induced plasticity have focused on documenting how prey species respond to predators by modifying phenotypic traits and how traits correlate with fitness. We have previously shown that Pleurodema thaul tadpoles exposed to the dragonfly Rhionaeschna variegata responded strongly by showing morphological changes, less activity, and better survival than non-exposed tadpoles. Here, we tested whether there is a functional link between morphological plasticity and increased survival in the presence of predators. Tadpoles that experienced predation risk were smaller, less developed, and much less active than tadpoles without this experience. Burst speed did not correlate significantly with morphological changes and predator-induced deeper tails did not act as a lure to divert predator strikes away from the head. Although we have previously found that tadpoles with predator-induced morphology survive better under a direct predator threat, our results on the functional link between morphology and fitness are not conclusive. Our results suggest that in P. thaul tadpoles (1) burst speed is not important to evade predators, (2) those exposed to predators reduce their activity, and (3) morphological changes do not divert predator attacks away from areas that compromise tadpole survivalEE. Our results show that morphological changes in P. thaul tadpoles do not explain burst speed or lure attraction, although there was a clear reduction of activity, which itself reduces predation. We propose that changes in tadpole activity could be further analyzed from another perspective, with morphological change as an indirect product of behavior mediated by physiological mechanisms.

Embryonic and larval defensive responses of agile frog (Rana dalmatina) to alien crayfish

“…Secondly, activity and morphology being highly integrated traits (Bourdeau & Johansson, 2012), morphological defenses may be a by-product of changes in prey behavior. Consistently, tadpoles from BC were more reactive to disturbance, as assessed by recording "bursts," and tail broadening has been reported to improve swimming and acceleration during predator escape (Van Buskirk Perotti, Pueta, Jara, Ubeda, & Azocar, 2016). Interpopulation variation in defensive responses may depend on adaptations to local environmental conditions-such as refuge availability, water turbidity, riparian and aquatic vegetation cover, and the composition of the predator community (Lima & Dill, 1990;Van Buskirk et al, 1997)-which are likely to affect risk perception by tadpoles.…”

Is thermal sensitivity affected by predation risk? A case study in tadpoles from ephemeral environments

“…Among ectotherms, anuran tadpoles are known to be good models for analyzing thermal sensitivity and thermal tolerance (Burggren & Warburton, 2007; Taylor et al, 2021), either because of their sensitivity to temperature as ectotherms or because of their ease of captive rearing, with locomotion being one of the traits used for estimating performance at different temperatures (Angilletta, 2009). Moreover, in anurans, swimming plays a fundamental role in survival, allowing them to escape from predators: they can either remain still, avoiding detection, or take the risk of being detected by escaping at full speed (Arendt, 2009; Dayton et al, 2005; Katzenberger et al, 2014; Perotti et al, 2016; Watkins, 1996).…”

Stress hormone-mediated antipredator morphology improves escape performance in amphibian tadpoles

“…Increased tail muscle depth has been hypothesized to improve escape swimming velocity (i.e., startle response) during a predator attack, a hypothesis that has received mixed support 21 – 25 . A concurrent increase in tail surface area also may lure strikes away from the more vital parts of the body 26 , a hypothesis that has received empirical support in ranids and other genera 23 , 27 .…”