Morphological variation of statolith of the jumbo flying squid (Dosidicus gigas) in the eastern Pacific Ocean

The jumbo flying squid(Dosidicus gigas)is one of important economic cephalopods with statolith providing important ecological information.According to the statolith morphology of the squid caught in waters off Chile,Peru and Costa Rica from May,2008 to Oct,2009,the differences of statolith morphology and growth patterns were analyzed.It was found that the statolith morphological characteristics in different areas had statistically significant differences(P<0.05).The length index and only the ventral dorsal dome angle(DDA)angle index had significant differences.The result of the principal component analysis was that total statolith length(TSL)was the most significant indicator of statolith morphology.The significant indicator of statolith angle was rostrum angle(RA)in waters off Chile and Peru,and rostrum lateral dome angle(RDA)in waters off Costa Rica.The growth of various parts was synchronized and allometric during the growth process,and the changing tendency of morphology was narrow body,long and narrow rostrum and large dorsal tallied with the characteristics of pelagic cephalopods statolith.Statolith growth consisted of two phases.According to the data of rostrum lateral dome length(RDL),there were marked differences in morphology between TSL smaller and larger than 1 600 μm.Based on the data of the angle,there were marked differences in RA between TSL smaller and larger than 2 000 μm in waters off Costa Rica,and 1 800 μm in waters off Peru,and there were marked differences in RA in waters off Chile.The angle increased later than the length of statolith,so TSL of 1 600 μm might be regarded as an valid indicator of changes in water layer.