Research Product

Hexavalent chromium was found to be an effective inhibitor of regenerative limb growth in grass shrimp. A dose-related inhibition of limb regeneration (fifth peripod) by chromium was observed, with total blockage of premolt limb bud growth at the highest concentration tested (4.0 ppm Cr), and greater than 50% inhibition at a concentration of 0.5 ppm. Histopathological studies of severely retarded limb regenerates suggest that Cr6+ causes abnormal alterations in the mitochondria, rough endoplasmic reticulum, and nuclei of the blastemal epithelium. In addition, there was an apparent reduction in the incidence of blastema mitoses. Nerve axon regeneration, upon which basal limb growth is presumably dependent, was adversely affected as evidenced in the markedly swollen axonal processes. The significantly greater sensitivity of the limb regeneration assay is demonstrated by the fact that the 96-h LC50 (0.41 ppm Cr) was an order of magnitude lower than the 96-h LC50 (4.86 ppm) for sensitive molting grass shrimp.