Statolith morphology of Gonatopsis borealis in the northwest Pacific Ocean

The morphology and microstructure of statolith of Gonatopsis borealis were studied for the 339 samples, which were collected by Chinese jigging fleets in the northwest Pacific Ocean from September to November 2018. The study indicated that the statolith has the structure with a wide wing and long, narrow rostrum domes. The principal component analysis showed that the total statolith length (TSL), rostrum lateral dome length (RLL), lateral dome length (LDL), wing length(WL) and maximum width (MW) could be used as the morphological characteristic parameters to study the morphological changes of statolith. The analysis of covariance (ANCOVA) showed that there were significant differences in the relationships between MW, LDL and WL versus mantle length (ML) between males and females, but no significant difference was found in other characteristic parameters. The relationships between all of the statolith characteristic parameters and body weight (BW) differed significantly. The relationships between TSL, RLL and ML were optimally described by the linear growth models, and power functions were optimal for WL, MW of males and LDL of males, however, exponential function was optimal for LDL of females. The exponential functions were optimal for the relationship between the LDL, MW of males, and linear functions were optimal for LDL, MW, TSL of females, and power function for the other parameters. With the squid growth, the size of statolith gradually increased, but the ratios of DLL, LDL, RLL, WL to TSL almost remain at the same level, corresponding to 35.66%, 55.84%, 75.23% and 85.82%, respectively.