Effects of pond water, sediment and sediment extract samples from New Hampshire, USA on early Xenopus development and metamorphosis: comparison to native species.

In an effort to assess potential ecological hazards to amphibian species in selected regions within New Hampshire, the traditional Frog Embryo Teratogenesis Assay-Xenopus (FETAX), a 14-/21 day tail resorption thyroid disruption assay and >30 day limb development tests were conducted with representative surface water and sediment samples. Two separate sets of samples collected from five sites were evaluated. The primary objectives of the study were to determine if samples were capable of inducing early embryo-larval maldevelopment, to determine if maldevelopment included limb defects, to determine if thyroxine co-administration altered the rates of limb malformation and to evaluate the impact of the samples on growth rates, developmental progress and metamorphic climax. Results from these studies suggested that pond water and sediment extract samples, but not whole sediment samples, from B2, FW, LP and W ponds were capable of inducing abnormal early embryo-larval development. In addition, water samples from B2 and W ponds induced significant abnormal hindlimb development. Some abnormal forelimb development was noted in the tail resorption studies, but not to the same extent as the hindlimbs. Each of the water samples induced appreciable developmental delay, including the paired reference site B1, which could be reversed by the addition of exogenous thyroxine.

Limb malformations and abnormal sex hormone concentrations in frogs.

Declines in amphibian populations, and amphibians with gross malformations, have prompted concern regarding the biological status of many anuran species. A survey of bullfrogs, Rana catesbeiana, and green frogs, Rana clamitans, conducted in central and southern New Hampshire showed malformed frogs at 81% of the sites sampled (13 of 16 sites). Brain gonadotropin-releasing hormone (GnRH) and the synthesis of androgens and estradiol, hormones essential to reproductive processes, were measured from limb-malformed and normal (no limb malformation) frogs. Normal frogs had significantly higher concentrations (nearly 3-fold) of in vitro produced androgens and of brain GnRH than malformed frogs. Because most malformations are thought to occur during development, we propose that environmental factors or endocrine-disrupting chemicals that may cause developmental abnormalities also act during early development to ultimately cause abnormally reduced GnRH and androgen production in adult frogs. The consequences of reduced GnRH and androgens on anuran reproductive behavior and population dynamics are unknown but certainly may be profound and warrant further research.