Contributions to Zoology, 86 (4) – 2017Jacques J. M. van Alphen; Jan W. Arntzen: The case of the midwife toad revisited

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Introduction

It is about a century ago that the Viennese biologist Paul Kammerer published his works on lizards, sea squirts and a variety of amphibian species. The results of his experiments invariably seemed to show that the animals he studied were plastic in their reproductive behaviour, colour or morphology when challenged with environments other than the natural one. Moreover, his data seemed to show that, in at least two species - the fire salamander and the midwife toad - these changes were inherited by next generations and thus evidence for Lamarckian evolution. Although his work was criticized by some of his contemporary colleagues, it lasted until long after the First World War before Paul Kammerer was publicly accused of scientific misconduct. The American herpetologist G. K. Noble inspected the last remaining specimen of a male midwife toad that was supposed to show nuptial pads, and found spots of injected Indian ink instead. This observation was published in Nature (Noble, 1926) and irremediably damaged Kammerer’s scientific credibility and the scientific community further ignored his work until 1971, when Arthur Koestler’s book “The Case of the Midwife Toad” renewed interest in Kammerer and his research. Koestler suggested that the midwife toad under scrutiny may have been tampered with by somebody else and depicted Kammerer as the victim of National Socialists sympathisers at the university of Vienna. He did not raise much doubt about the other research being genuine and discounted the possibility that Kammerer would have been a fraud himself. Recently, new publications have appeared, building on Koestler’s (1971) speculations, suggesting that Kammerer was not only the victim of an anti-Semitic conspiracy (Taschwer, 2016), but also a scientist ahead of his time, reporting the first evidence for epigenetics (Vargas, 2009; Vargas et al., 2016).

Evidence for the role of epigenetics in evolution is scarce or absent. If Vargas (2009) and Vargas et al. (2016) would have been right, Kammerer would also have been the first person to provide evidence for the role of epigenetics in evolution. Although plants have diverse pathways overseeing the faithful passage of the methylome to daughter cells, there is little evidence that the environment induces changes in DNA methylation in plant genomes (Wibowo et al., 2016; Akst, 2017). In animals it is even less likely that environmentally induced epigenetic changes are passed on to the next generation, because the CG marks are wiped out in two rounds of reprogramming in the gamete and the early embryo. It thus remains controversial whether germline DNA methylation in animals remains stably heritable (Nagase and Gosh, 2008).

We reviewed Kammerer’s research on fire salamanders and blind cave salamanders and concluded that it was Kammerer himself that committed fraud in these studies (van Alphen & Arntzen, 2016). As the claims for Kammerer being the first to find evidence for epigenetics are based on his work on midwife toads, we decided to review Kammerer’s experiments on this species as well, and evaluate if epigenetics could explain the results. The reason behind our effort is that Vargas (2009) and Vargas et al. (2016) only deal with a simplified version of the results of Kammerer’s experiments and fail to mention important details that would also have to be explained by epigenetics, but are hard to reconcile with present day knowledge.