Studies of the genetic and physiological alterations in cadmium-resistant Biomphalaria alexandrina: Implication of susceptibility to molluscicides and Schistosoma mansoni infection.

Abstract

Abstract Biomphalaria alexandrina snails were examined for their tolerance to cadmium (Cd) toxicity through three generations produced by self-fertilization by exposing snails to serial concentrations of Cd and selection for the most tolerant ones through the successive generations. Results showed a gradual increase in the LC50 and LC90 values through successive generations indicating tolerance upgrading phenotype. Also, the selected Cd-tolerant third generation snails (G3), non-selected laboratory breeding snails and field snails were examined for the toxicity of chemical and plant molluscicides, bayluscide and Anagallis arvensis, respectively and other heavy metals, zinc (Zn), copper (Cu) and lead (Pb). The selected Cd-tolerant third generation (G3) showed higher LC50 and LC90 values for A. arvensis and Cu than each of non-selected laboratory breeding and field groups. The selected and non-selected snails were examined for their susceptibility to Schistosoma mansoni infection and physiological criteria (haematological and biochemical). The selected snails showed refractory tendency and a significant increase in haemocytes; granulocytes; which indicated that their defence mechanism was stronger than non-selected ones. Biochemical criteria indicated that selected Cd-tolerant group had stable liver enzymes and protein levels while had increase in the levels of urea (significant) and creatinine (non-significant) indicating that the liver cells were still intact while renal cells were affected. On the other hand, field group was the most affected followed by laboratory one.