Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

Summary of Detoxifiction Processes
Mechanisms of detoxification vary among aquatic biota and include processes such as
translocation, excretion, chelation, adsorption, vacuolar storage, and deposition. Lead
detoxification has not been studied extensively in aquatic organisms, but existing results indicate
the following:
• Protists and plants produce intracellular polypeptides that form complexes with Pb (Zenk,
1996; Morelli and Scarano, 2001).
• Macrophytes and wetland plants that thrive in Pb-contaminated regions have developed
translocation strategies for tolerance and detoxification (Knowlton et al., 1983; Deng et al.,
2004).
• Some starfish (asteroids) sequester the metal via mineral deposition into the exoskeleton
(Boisson et al., 2002).
• Species of mollusc employ lysosomal-vacuolar systems that store and chemically process Pb
in the cells of their digestive and pericardial glands (Giamberini and Pihan, 1996; AbdAllah
and Moustafa, 2002).
• Decapods can efficiently excrete Pb (Vogt and Quinitio, 1994; Giamberini and Pihan, 1996)
and sequester metal through adsorption to the exoskeleton (Knowlton et al., 1983).
• Fish scales and mucous chelate Pb in the water column, and potentially reduce visceral
exposure.
Avoidance Response
Avoidance is the evasion of a perceived threat. Recent research into heavy metal
avoidance in aquatic organisms has looked at dose-response relationships as well as the effects of
coincident environmental factors. Preference/avoidance response to Pb has not been extensively
studied in aquatic organisms. In particular, data for aquatic invertebrates is lacking.
Using recent literature, this section examines preference-avoidance responses of
invertebrates and fish to Pb and some other environmental gradients.
Aquatic Invertebrates
Only one study was identified on avoidance response in aquatic invertebrates. Lefcort
et al. (2004) studied the avoidance behavior of the aquatic pulmonate snail Physella columbiana
from a pond that had been polluted with heavy metals for over 120 years. In a Y-maze test, first
generation P. columbiana from the contaminated site avoided Pb at 9283 µg/L (p < 0.05) and
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