Lead tolerance in the freshwater isopod asellus aquaticus

Abstract

After a survey of the occurrence of Asellus aguaticus in South Lancashire rivers, one site on the polluted river Calder and another on the unpolluted Woodplumpton Brook were selected for further investigation. Calder Asellus were shown to be more tolerant to lead than Woodplumpton Asellus but there was no difference between the populations in their tolerance to copper, zinc, cadmium or arsenic.
Calder Asellus took up more lead from solution than Woodplumpton Asellus at concentrations from 1-300 mg/I, but less at concentrations from 300 to 500 mg/I. Neither population took up lead from food (decaying sycamore or lettuce leaves).
Comparison.of lead lost from the medium with lead gained by Asellus showed that lead was accumulated on the sides of the containers only in the presence of Asellus. This was found to be due to micro-organisms.
Antibiotic treatment decreased lead uptake on the containers and in the Asellus. Two 6pecies of lead-accumulating bacteria, Aeromonas punctata and Citrobacter freundii, were isolated from Asellus and their environment. Experiments using an anti-microbial agent 'Steralize' showed that lead tolerance in both populations was increased in a medium of distilled water, but decreased in 0.025 M CaCl2. Steralize' also increased lead uptake from a freshwater medium. Dissection. experiments showed that lead was accumulated mainly in the cuticle or its underlying tissues:
Lead inhibited oxygen uptake in both populations. Calder Asellus took up more oxygen than Woodplumpton animals in distilled water and in 0.025 M CaCl2, but there was no difference between the populations in river water or in freshwater medium.
Pre-treatment of Asellus with 0.1 mg/l Pb caused the tolerance of large and medium-sized Woodplumpton Asellus to increase to the level of untreated Calder animals. Large Calder Asellus were made less tolerant by pre-treatment, but there was no significant effect on medium sized animals. It was concluded that lead tolerance in A. aguaticus is mainly due to acclimation.