Transcriptome analysis of predator‐ and prey‐induced phenotypic plasticity in the Hokkaido salamander (Hynobius retardatus)

Abstract

Predator- and prey-induced phenotypic plasticity is widely observed among amphibian species. Although ecological factors inducing diverse phenotypic responses have been extensively characterized, we know little about the molecular bases of variation in phenotypic plasticity. Larvae of the Hokkaido salamander, Hynobius retardatus, exhibit two distinct morphs: the presence of their prey, Rana pirica tadpoles, induces a broad-headed attack morph, and the presence of predatory dragonfly nymphs (Aeshna nigroflava) induces a defence morph with enlarged external gills and a high tail. To compare the genes involved in predator- and prey-induced phenotypic plasticity, we carried out a de novo transcriptome analysis of Hokkaido salamander larvae exposed to either prey or predator individuals. First, we found that the number of genes involved in the expression of the defence morph was approximately five times the number involved in the expression of the attack morph. This result is consistent with the fact that the predator-induced plasticity involves more drastic morphological changes than the prey-induced plasticity. Second, we found that particular sets of genes were upregulated during the induction of both the attack and defence morphs, but others were specific to the expression of one or the other morph. Because both shared and unique molecular mechanisms were used in the expression of each morph, the evolution of a new plastic phenotype might involve both the co-option of pre-existing molecular mechanisms and the acquisition of novel regulatory mechanisms.

Plasticity and evolutionary divergence in gene expression associated with alternative habitat use in larvae of the European Fire Salamander

“…Our work warrants analysis of additional ecological factors using the same framework. This could include physical parameters reflecting different seasons or biotic factors such as food items or predators (Matsunami et al., ). A more complete understanding of effects caused by multiple and experimentally controlled ecological factors might contribute to explain why colonization of new habitats is sometimes realized by the same transcriptional plasticity and differentiation responses (Schneider & Meyer, ), or in contrast by largely different sets of genes, as we have found in a comparison between pond and stream salamander larvae in S. salamandra and the Near Eastern Fire Salamander ( S. infraimmaculata ) (Goedbloed et al.…”

Differences in perceived predation risk associated with variation in relative size of extra‐pair and within‐pair offspring

“…Likewise, tadpoles of many amphibians are known to develop specialized defensive traits in response to cues that signal heightened predation risk (e.g. Matsunami et al, ). In each of these examples, the key is that offspring bearing different phenotypes each perform well under a particular set of environmental conditions and fare relatively poorly when these conditions are absent.…”

Mechanisms underlying the control of responses to predator odours in aquatic prey

“…Hokkaido salamander larvae (Hynobius retardatus) express five times the number of genes when inducing a defensive (antipredator) morphology following exposure to odours and diet cues from a predator (Aeshna nigroflava) than when inducing a predatory (foraging) morphology following exposure to food cues from the prey, Rana pirica; the difference in gene expression probably reflects the heavier investment required to express the defensive compared with the predatory morphotype (Matsunami et al, 2015). In both cases, genes related to responses to reactive oxygen species were upregulated to account for the increased metabolic demand of morphogenesis.…”