Karplus, I., Agricultural Research Organization, Fish and Aquaculture Research Station, Dor, M.P. Hof Hacarmel 30 820, Israel
Barki, A., Agricultural Research Organization, Fish and Aquaculture Research Station, Dor, M.P. Hof Hacarmel 30 820, Israel
Israel, Y., Agricultural Research Organization, Fish and Aquaculture Research Station, Dor, M.P. Hof Hacarmel 30 820, Israel
Cohen, S., Agricultural Research Organization, Fish and Aquaculture Research Station, Dor, M.P. Hof Hacarmel 30 820, Israel

Bi-weekly recordings of size and morphotype of individually marked Macrobrachium rosenbergii raised in large communal cages support the "leapfrog" hypothesis, i.e. the orange-clawed male (OC) metamorphoses into the blue-clawed male (BC) only after becoming larger than the largest BC male in its vicinity. This results in a series of differently sized BC males, whose size is positively correlated with the time of their metamorphosis. This growth pattern is achieved mainly through a delay in the transition from the fast growing OC morphotype into the slow growing BC one. This delay may be due to social interaction among males, as males isolated in small cages did not follow this pattern. The function of the "leapfrog" growth pattern is discussed. © 1991.