The introduction of Xenopus laevis into developmental biology: of empire, pregnancy testing and ribosomal genes.

Abstract

The ever greater concentration of biomedical research on fewerand fewer species is a striking general feature of the postwar era. Indevelopmental biology, the South African clawed frog Xenopuslaevis is, with Drosophila, the mouse, the chick, C. elegans and thezebrafish, one of only half-a-dozen ‘model’ organisms used for thevast majority of research. How did a species which occurs naturallyonly in Southern and Central Africa rise to such international promi-nence? Developmental biologists routinely answer this question bylisting the main reasons currently assembled for using Xenopus:ease of maintenance of a wholly aquatic vertebrate in the laboratory;exceptional resistance to disease; a life cycle that among Amphibiais relatively short; large numbers and size of eggs suitable formicrosurgery; and above all its year-round reproductive response tocommercial hormone preparations compared to the limited breedingseasons of other amphibians (Kay and Peng, 1991; Tinsley andKobel, 1996). Another kind of answer is historical, and this is what weoffer here.From the 1880s and the early work of Wilhelm Roux and othersin Germany, experimental embryologists favoured Amphibia(Beetschen, 1996; Nieuwkoop, 1996), but they used the localEuropean and North American species, initially mostly of the frogRana (Maienschein, 1991). By the early twentieth century urode-les were preferred; Hans Spemann (Hamburger, 1988; Fasler,1997) experimented mainly on species of the newt Triton (nowTriturus) and Ross Harrison on the axolotl Amblystoma . FollowingSpemann in the 1930s, even Joseph Needham and colleagues’biochemical analysis of the organizer used newts (Haraway,1976). Only during and after World War II did Xenopus begin itsrise to dominance. But developmental biologists in Europe andNorth America did not choose an African frog after a detached andcomprehensive survey of world fauna. It turns out that the intro-duction of Xenopus into developmental biology laboratories wasmore fortuitous, and is more interesting. Its eventual embryologi-cal exploitation was made possible by specific histories of empireand of endocrinology which happen to have centred to a substan-tial extent in Britain; demand was ensured by a reorientation ofembryology towards biochemical methods. Here we trace thescientific domestication of the South African clawed frog, focusingespecially on how, between the 1930s and the early 1960s, it wasintroduced into European and North American laboratories, wherenot only developmental biologists but also converts from bio-chemistry took it up.