Adaptive acceleration in growth and development of salamander hatchlings in cannibalistic situations

Abstract

Summary 1.In most animal species, the hatchling stage is a highly vulnerable life-history stage. In many fish and amphibian species, hatchling abundance varies substantially among sites and years, with the result that selection strength in conspecific interactions such as cannibalism is also variable. The variability of selection leads species to evolve phenotypic plasticity, and adaptive trait changes in hatchlings that depend on the density of conspecifics can therefore be expected. However, plasticity strategies in response to cannibalistic interactions in this vulnerable life-his tory stage have received little attention. 2. Because cannibalism success is dependent on the size balance between predator capturing organ and prey body, and also on the prey-capturing ability of the cannibal and the escape ability of its prey, we hypothesize that hatchlings will exhibit faster growth and development in response to conspecific interactions. We performed a series of experiments to test this hypothesis, using pre-feeding larvae of a cannibalistic salamander (Hynobius retardatus). 3. Many traits of the hatchlings reared with conspecifics were larger than the same traits in those reared alone, because the former hatchlings grew faster and were more advanced developmentally. The time to the beginning of feeding was shorter, and swimming speed as an indicator of escape performance was faster, for hatchlings reared with conspecifics. 4. Hatchlings reared with conspecifics more successfully cannibalized small hatchlings and were also highly resistant to being cannibalized by large conspecifics, compared with hatchlings reared alone. These differences in cannibalism success and avoidance of cannibalization were well explained by differences in gape and head size, respectively, between the interacting hatchlings. Therefore, acceleration of growth and development of hatchlings in the proximate presence of conspecifics may confer significant fitness advantages on hatchlings in a high-density cannibalistic situation. 5. Developmental and growth plasticity may thus be a powerful adaptive mechanism that allows individuals to respond to the dynamic character of salamander populations in nature.

Foraging traits of native predators determine their vulnerability to a toxic alien prey

“…In Experiment 3, we found that H. retardatus salamander larvae were 83% more likely than R. pirica frog tadpoles to attack and consume the accessible toad hatchling (Result 3.1.1). This is reasonable considering that H. retardatus salamander larvae specialise in consuming amphibian larvae (Kishida, Tezuka, Ikeda, Takatsu, & Michimae, 2015;Kishida, Trussell, & Nishimura, 2009;Wakahara, 1995;Yamaguchi, Takatsu, & Kishida, 2016), in contrast to the opportunistic R. pirica frog tadpoles. Nevertheless, we found that the consumption rate of frog tadpoles was 338% greater than that of salamander larvae in the aquarium experiment (Experiment 2, .…”

Trade‐offs affect the adaptive value of plasticity: stronger cannibal‐induced defenses incur greater costs in toad larvae

“…Although most frequently studied in marine organisms (Oyarzun and Strathmann 2011), a pre‐feeding larval period also occurs in many amphibians, and may also be targeted by stage‐specific threats. These larvae can be extremely vulnerable immediately after their emergence from the protective egg capsule due to their small size, limited defenses, and low motility (Kishida et al 2015). Pre‐feeding larvae can respond to environmental cues, including cannibalism (Kishida et al 2015) and food limitation (Adams et al 2011), and such responses can negatively affect subsequent performance (Marshall et al 2003).…”

Size‐mediated priority and temperature effects on intra‐cohort competition and cannibalism in a damselfly

“…The size advantage might also result in predation by the early‐hatched individuals on the smaller individuals that hatched later. Such predation at the intraspecific level, that is cannibalism, has the potential to affect the survival, development and growth of individuals in a population (Eitam et al., ; Hopper, Crowley, & Kielman, ; Kishida, Tezuka, Ikeda, Takatsu, & Michimae, ). At the population level, cannibalism results in a more even size distribution and tends to stabilize population dynamics (Claessen, De Roos, & Persson, ).…”