A study of normal and regenerative growth in the pistol-crab, alpheus dentipes (Guèr.), with special reference to the phenomenon of chela reversal.

An analysis has been made of the normal growth of the thoracic appendages in the pistol-crab,Alpheus dentipes. The chelae are the only asymmetrical appendages and, within an extensive size range, the growth-coefficient of the large chela (crusher) is smaller than that of the small chela (nipper), even in the most rapidly growing dimensions of the segment containing the growth-centre.The partition coefficient for growth in certain dimensions of the chelae is not constant but is reduced progressively during the growthperiod, due (it is suggested) to the impracticability of maintaining the intensive heterogony developed during the early stages of growth.Regenerative growth of the chelae has been studied quantitatively after autotomy of one, the other, or both normal chelae, effected once only or repeatedly as new chelae appeared at moulting. New chelae are regenerated repeatedly with little or no waning of growth intensity but in continuously growing chelae, growth intensity is substantially reduced at the end of the instar of autotomy. The amount of growth is not correlated with thenumber of days available for regeneration. When both chelae regenerate simultaneously the larger one grows relatively slower than the smaller one to the end of the instar of autotomy but afterwards this condition is reversed. When the nipper alone is autotomised, growth of the crusher is inhibited and shrinkage may occur. Crusher autotomy, on the other hand, stimulates nipper growth and to an extent which varies with the dimension.The problem of chela reversal has been discussed and certain suggestions have been preferred.