A feral population of African clawed frogs Xenopus laevis from a small pond
in South Wales was sampled continuously for 2 years to assess morphometric
growth. Toe-clips taken at intervals over a 4-year period were found to co
ntain lines of arrested growth (LAG) which corresponded to each consecutive
winter. The first toe-clips revealed a population structure within the pon
d consisting of a dominant cohort of frogs with one LAG that metamorphosed
in 1993, and a few older individuals. Subsequent toe-clips in 1996 and 1998
gave two and four more LAG, respectively. Morphometric growth was found to
be restricted to a short growing season, significant differences in the gr
owth rates of males and females being first detected in their third growth
season. Reproductively active frogs were still within their initial period
of growth, suggesting that Xenopus laevis does not conform to the standard
energy resource allocation mechanisms of typical ectotherms.