Assessment of Crab Limb Regeneration as an Assay for Developmental Toxicity

The regeneration of a cheliped that is autotomised at the final larval stage, the megalopa, of the mud crab Rhithropanopeus harrisii (Gould) forms the basis of an assay for developmental toxicity. Cheliped regeneration is followed through to the third juvenile crab stage; a regenerate that is approximately two thirds full size normally emerges at the moult to the second crab, and full size is attained at crab 3. The absence of a regenerate at crab 2, or a regenerate that is smaller than normal and/or malformed, is scored as abnormal regeneration. Other parameters examined in this assay include survival and duration of development. The assay is of comparatively short duration (approximately 2 wk), and survival is high following autotomy under optimal conditions. Four insecticides and a herbicide have been tested in the assay at lethal and sublethal concentrations. Of these compounds, methomyl, carbofuran, and alachlor induced abnormal regeneration whereas cypermethrin and RH 5849 did not affect regeneration at the concentrations tested. Although reproducibility of results needs improvement, crab limb regeneration is otherwise a practical assay for developmental toxicity.