Heavy metal toxicity of kidney and bone tissues in South Australian adult bottlenose dolphins (Tursiops aduncus).

Metallothioneins (MT) concentration, renal damage, and bone malformations were investigated in 38 adult Tursiops aduncus carcasses to determine any associations with cadmium, copper, zinc, mercury, lead and selenium. Significantly higher concentrations of cadmium, copper, and zinc in the liver were observed in dolphins showing evidence of more advanced renal damage. No significant differences in metal or selenium concentrations in the liver were observed between groups differing in level of bone malformations. Some dolphins displayed evidence of toxicity and knowledge of metal toxicity pathways were used to elucidate the cause of these abnormalities. Two dolphins had high metal burdens, high MT concentrations, renal damage, and evidence of bone malformations, indicating possible severe and prolonged metal toxicity. One dolphin showed evidence of renal damage, but the lack of any other symptoms suggests that this was unlikely to be caused by metal toxicity. We recommend examining a range of metal toxicity symptoms simultaneously to aid in distinguishing metal toxicity from unrelated aetiologies.

Metals and selenium in the liver and bone of three dolphin species from South Australia, 1988-2004.

Metal and selenium concentrations (wet weight) were determined in the liver (Cd, Hg, Pb, Zn, Cu and Se) and bone (Pb and Cd) of common dolphins (Delphinus delphis, N=71) and bottlenose dolphins (Tursiops truncatus, N=12, and Tursiops aduncus, N=71) stranded or by-caught in South Australia from 1988 to 2004. Differences in metal burdens existed between species, stranding location, and relative age. T. aduncus had the greatest mean tissue burdens of liver Pb (0.45 mg/kg), Cd (6.45 mg/kg), Hg (475.78 mg/kg), Se (178.85 mg/kg) and Zn (93.88 mg/kg) and bone Pb (2.78 mg/kg), probably reflecting their coastal habitat and benthic prey. Mean Cu was highest in T. truncatus (21.18 mg/kg). Bone Cd was measured only in T. aduncus and averaged 0.05 mg/kg. Stranding location impacted metal burdens. Dolphins from Spencer Gulf had higher mean levels of liver Pb (0.39 mg/kg) while Gulf St Vincent dolphins had greater liver Hg (444.64 mg/kg), liver Se (163.12 mg/kg), and bone Pb (2.85 mg/kg). This may be due to high anthropogenic inputs of Pb and Hg into Spencer Gulf and Gulf St Vincent respectively. Liver Cd, Hg, Se and Pb increased with age in all species while Cu decreased with age, in keeping with previous studies. Se and Hg were positively correlated. The possibility that metallothioneins are driving observed correlations between Zn, Cd, Hg and Cu are discussed. Future research must investigate the toxicological consequences of the metal concentrations reported.

Neurogenesis in septum, amygdala and hippocampus in the marsupial brushtailed possum (Trichosurus vulpecula)

The times of origin of neurons in the septum, amygdala and hippocampus of the marsupial brushtailed possum, Trichosurus vulpecula, were determined with 3H thymidine autoradiography. The long time period for neurogenesis in the brushtailed possum facilitated analysis of neurogenetic gradients in the brain. A series of 20 possums were injected with 3H thymidine from postnatal (P) days 5-95 and were allowed to survive until brain cytoarchitecture was mature. Our results indicate that septal neurogenesis was complete by P21 (38 days after conception) with a medial to lateral gradient of neurogenesis evident in the lateral septal division. Neurogenesis in the amygdala was complete in the basal, central and medial amygdaloid nuclei by P21, and in the lateral amygdaloid nucleus by P46, with a medial to lateral gradient of neurogenesis evident in basal, central and lateral amygdaloid nuclei. In the hippocampus, neurogenesis of pyramidal cells was complete in field CA3 by P50, and in field CA1 by P55. Early forming pyramidal cells (P5-12) were distributed adjacent to the stratum oriens in fields CA1 and CA3, with later forming pyramidal cells distributing in the middle of the stratum pyramidale (P21-32) and on the edge adjacent to the stratum radiatum (P46). Neurogenesis of dentate granule cells extended over a long period of time, from P5, at least until P82, with the earliest forming granule cells (P5-12) distributed adjacent to the stratum moleculare, and the latest forming granule cells (P82) adjacent to the hilus.