Selenium–lead interactions in crawfish (Procambrus clarkii) in a controlled laboratory environment

Abstract

To determine whether the relationship between selenium and lead is one of an antagonistic or synergistic nature, experiments were conducted on the freshwater crustacean crawfish or crayfish (Procambarus clarkii). Crawfish were exposed to a known concentration of lead, dissected then analyzed to determine the accumulation of lead and found as follows: gills>exoskeleton>organs>edible meat. Duplicates of the lead exposed crawfish were exposed to a concentration of approximately 10ppm (mg/L) selenium for a week to determine any adverse physiological effects. Analysis of the selenium exposed crawfish revealed time dependent and tissue specific adsorption of selenium identical to the concentrations of the lead exposed crawfish: gills>exoskeleton>organs>edible meat.After exposure to selenium, the crawfish were still living in a complete state of paralysis for seven days. Duplicates were placed in pure water to determine the ability of the crawfish to purge the selenium and regain mobility. Within 24h of purging, eighty-eight percent of the paralyzed crawfish had regained full motor skills. Analysis of the purged crawfish showed a significant decrease in the concentration of selenium in the chitin rich exoskeleton and gills. However, the lead concentration in the gills and exoskeleton of the purged versus non-purged crawfish did not show any significant decrease indicating that the bond between the chitin and lead is much stronger than the bond between the selenium and chitin and/or lead. Proposed mechanisms for each bond are presented in this research.