Showing papers on "Bufo melanostictus published in 2008"

Effects of diazinon on larvae of the Asian common toad (Bufo melanostictus, Schneider 1799).

Abstract: Continuous subchronic exposure experiments were conducted to assess the effects of diazinon, an organophosphate pesticide, on the survival, growth and activity of larvae of the Asian common toad Bufo melanostictus. Two larval stages, the gill stage (Gosner stages 21 and 22) and gill-atrophy stage (Gosner stages 24 and 25), were continuously exposed to 4 μg/L, 400 μg/L, and 10 mg/L of commercial-grade diazinon for 30 d. Treatments and untreated controls were maintained in triplicate with water changed and pesticide concentrations renewed every 3 d. Observations showed that subchronic exposure to 400 μg/L and 10 mg/L diazinon caused a significant dose-dependent increase in mortality compared to the control, regardless of the age at which larvae were exposed. One hundred percent mortality was observed in larvae exposed to 10 mg/L. No clear age-related sensitivity was evident in this study. The lethal concentrations at which 50% of the tadpoles (LC50) died during 30 d of continuous exposure were 6 and 7.5 mg/L for gill stage and gill-atrophy stage larvae, respectively. Diazinon impaired larval growth and activity. Tail abnormalities were apparent in larvae exposed to 400 μg/L and 10 mg/L of diazinon. This investigation provides the first empirical evidence of the negative effects of diazinon on the survival, growth and activity of B. melanostictus. The high degree of diazinon toxicity in this study highlights the need to consider important nontarget groups when recommending safe levels of pesticide application.

The Identification of the Sex Chromosome and Karyotype of Four Toad Species (Genus Bufo) in Thailand by T-lymphocyte Cell Culture

Abstract: Our knowledge is the first report on karyotypic study of four toad species (genus Bufo) in Thailand namely; large-eared toad (Bufo macrotis Boulenger 1887), Indochinese dwarf toad (Bufo parvus Boulenger 1887), common Indian toad (Bufo melanostictus Schneider 1799) and river giant toad (Bufo asper Gravenhorst 1829). Blood samples were taken from 5 males and 5 females of each four toad species. After the standard whole blood T-lymphocyte culture in the presence of colchicine, the metaphase spreads were performed on microscopic slides and air-dried. Conventional staining, G-banding and C-banding techniques were applied to stain the chromosomes. The results indicated 2n=22 and fundamental number (NF) 44 in both male and female of four toad species. The autosomes of B. macrotis and B. melanostictus is being as 18 metacentric and 4 submetacentric chromosomes while B. parvus and B. asper is as 16 metacentric and 6 submetacentric chromosomes. G-banding technique showed a B. melanostictus's constriction on short arm of Y chromosome (the largest chromosome) but did not show on X chromosome. C-banding technique demonstrated a dark band constriction on Y chromosome of B. melanostictus, the representative of constitutive heterochromatin. However, there is no dark band constriction on X chromosome. So, we conclude that the sex determination of B. melanostictus is XY system. Although we do not treat B. macrotis, B. parvus and B. asper with G-banding and C-banding technique, we also predict that those three species have the same sex determination as B. melanostictus. We extremely appreciate to public our present research, the first cytogenetic study of B. macrotis and B. asper.

Effects of diazinon on survival and growth of two amphibian larvae

Abstract: Amphibian populations are declining globally at an alarming rate and evidence suggests that pesticides may be a principal cause. The present study investigated the effects of diazinon on the survival and growth of larvae of two amphibians, Bufo melanostictus (Asian common toad) and the Sri Lankan endemic Polypedates cruciger (Common hourglass frog). Larvae were laboratory bred from egg clutches collected from ponds and wells in home gardens in the Gampaha and Colombo districts. Two separate trials were conducted using gill stage hatchlings (Gosner stages 20-22) of each species. The larvae were repeatedly exposed to 4 μg/L, 400 μg/L and 10 mg/L of diazinon for seven days. Results showed that exposure to 10 mg/L of diazinon caused significant elevations (p B. melanostictus and P. cruciger as compared to the controls. No significant increases in mortality were noted at 4 μg/L and 400 μg/L. The trends in mortality were significant and positive for both species. Growth retardation was also noted at the highest dose of 10 mg/L, these larvae being significantly smaller than those in the controls (p Keywords: Amphibian, Bufo melanostictus , diazinon, mortality, organophosphate pesticide, Polypedates cruciger , tadpoles doi:10.4038/jnsfsr.v36i2.149 Journal of the National Science Foundation of Sri Lanka 36 (2) 165-169