Microstructure of statolith and beak for Dosidicus gigas and its determination of growth increments

In order to research the application of microstructures of statolith and beak to age validation of jumbo flying squid, the samples of the jumbo flying squid were collected by the Chinese squid jigger fleet during July to October in 2013.The statolith, upper beak and lower beak were extracted from 39 samples.Their microstructures were analysed and the growth increments were counted.Meanwhile, the differences between the numbers of statolith, upper beak and lower beak increments were analysed by variance analysis.Results showed that the increments in the dorsal region of the beak's hood were more complete.And to avoid the tip erosion effects, the first increments could be counted in the dorsal area of the rostral sections.This study found that the microstructures of the upper and lower beaks were very similar, and both of them contained longitudinal increments and internal rostral axis.However, in terms of the morphology and the pigmentation process, there are differences between the microstructures of upper and lower beaks.Results indicated that the growth increments of the upper and lower beaks obtained were lineally related with that of the statolith.Values of r² and slope close to 1 were obtained(P < 0.01).Results indicated that both of the microstructures of the upper and lower beaks can better estimate the age of the jumbo flying squid.And the beak should be widely used in the research of age and growth of cephalopod.