Deformities in cane toad (Bufo marinus) populations in Bermuda: Part III. Microcosm-based exposure pathway assessment

Abstract

Short-term embryo-larval, limb development, and a battery of toxicity identification studies using sediment and water collected from selected ponds found that developmentally toxic samples contained elevated levels of petroleum hydrocarbons and As, Cu, Pb, Cr, Cd, Hg, Fe, and Zn. Sediments spiked with diesel fuel or metals confirmed that the levels of petroleum hydrocarbons and metals found in the sediment were capable of inducing developmental toxicity individually. However, joint mixture interaction studies indicated that the metals and petroleum hydrocarbons acted synergistically. To more rigorously evaluate exposure pathways and the effects induced, chronic laboratory-based microcosm experiments were performed using B. marinus from early embryo to metamorphosis. Results from these microcosm studies indicated that reasonably consistent frequencies of malformations were induced by exposure to contaminated media samples from four contaminated sites compared with frequencies found in field-collected specimens. The frequencies of specific types of deformities in newly metamorphosed organisms from the microcosm studies and in free-roaming field-collected specimens were also similar. Exposure to contaminated media from three of the four sites decreased the frequency of metamorphic completion and at one site reduced the metamorphic rate, compared to exposure to laboratory controls or reference media. Elevated whole body petroleum hydrocarbons and metals tissue residues were detected in organisms from the laboratory microcosms, as well as in the free-roaming specimens collected. To evaluate the impact of maternal contaminant transfer as an exposure route, cross-over exposure studies in which reference organisms were raised, from embryos through metamorphosis, in contaminated media and organisms from a contaminated site were cultured in reference media were conducted. Results from these studies indicated that environmental exposure and maternal toxicant transfer were the potential exposure routes. Overall, the present studies suggested the petroleum hydrocarbons and metals that accumulated in B. marinus during development in microcosms corresponded with increased frequencies of malformation.

Malformation in three anuran species from a preserved remnant of Atlantic Forest in southeastern Brazil

“…The only record in Brazilian anurans was in hybrids of Rhinella icterica (Spix, 1824) with Rhinella crucifer (Wied-Neuwied, 1821), where hybridization seemed to have caused the deformities (Haddad et al 1990). There is evidence that increased rates of microphtalmia in anurans may be caused by exposition to heavy metals (Fort et al 2006). Another possible cause of microphtalmia has been suggested to be caused by Ranavirus FV 3 (Burton et al 2008), but there was no literature on experimental test to evidence it.…”

Status And Conservation Of The Reptiles And Amphibians Of The Bermuda Islands

“…More recently, cross-over exposure studies, in which B. marinus embryos from contaminated sites were raised in reference site media and vice versa, showed that there was also a marked maternal effect on larval development and survival. These studies suggested that metals and petroleum hydrocarbons were being transferred from the mother to her eggs during oogenesis and oocyte maturation, and that this transfer of contaminants had a marked impact on larval development and survival (Fort et al, 2006b). In summary, investigations to date indicate that survival and development of B. mar-inus larvae in Bermuda are being affected both by contaminants found in a number of its ponds and by transgenerational transfer of accumulated contaminants.…”

A case of bilateral anophthalmy in an adult Boana faber (Anura: Hylidae) from southeastern Brazil

“…However, the deformed Boana faber was collected in an area with varying levels of disturbance because the reserve is located in an agricultural matrix where pesticides can accumulate in bodies of water (Tabanez et al 2005). In fact, pesticides are known to cause deformities in embryos and larvae and to produce high rates of eye anomalies in adults (e.g., Bufo marinus; Fort et al 2006).…”