Tributyltin is a teratogen in producing deformities in limbs of the fiddler crab,Uca pugilator

Abstract

Exposure to tributyltin (TBT) produces deformities in regenerating limbs of the fiddler crab,Uca pugilator. This study was designed to ascertain whether there was a “sensitive period” during the four-week regeneration time following multiple autotomy, during which TBT exposure was more likely to result in malformations. Groups of crabs underwent autotomy of the chela plus five walking legs, and were exposed to 5.0 or 0.5 μg/L TBT continuously or only during week one, week 2, week 3, or week 4. Regeneration was monitored, and after ecdysis regenerated limbs were examined. The degree of malformation was evaluated on a scale, and for each crab the scores for each of its abnormalities were added together to arrive at an “abnormality index.” While the mean abnormality indices for crabs exposed during week one or week four were quite low, the indices for those exposed during week two were comparable to those of crabs exposed continuously, and those exposed during week three were only slightly lower. This indicates that the sensitive period is during weeks two and three, which is the time of basal growth, when the major events of differentiation and morphogenesis take place. Males were much more susceptible than females, due to the greater sensitivity of their regenerating major chela, compared to the minor chela of females. For both sexes, the regenerating chela was responsible for most of the abnormality index, even though there were five walking legs regenerating also.