Comparative Analysis Of Pigmentation Characteristics Regularityon Beak For Cephalopods From Different Families

Cephalopods were rich in resources and had high nutritional value.Cephalopod was one of the important fishing objects in the world fishery.The world cephalopod catch reached its peak in 2014,with a catch of 4,857,900 tons.China was one of the major cephalopod producing countries,and cephalopod fishery had become an important part of China’s offshore fishery.Cephalopod resources had great development potential,including Gonatidae resources and Ommastrephidae resources.Beak was an important feeding organ of cephalopods,with stable morphological structure and abundant information of fishery biology and ecology,which was widely used in cephalopods species identification and population structure division.Pigmentation was one of the important growth changes of beak,which can reflect the change of cephalopods’feeding habits and also affect the feeding behavior of cephalopods.In this paper,the pigmentation characteristics of beak of Gonatopsis borealis,Sthenoteuthis oualaniensis,Berryteuthis magister shevtsovi and Todarodes pacificus were studied,and the pigmentation stage of cephalopod beak in four different seas were compared and analyzed,so as to make use of the pigmentation of beak in the future.According to the samples collected by Chinese squid fishing boats in the northwest Pacific Ocean,the northwest Indian Ocean,the Sea of Japan and the East China Sea during the production survey in 2018-2019,the fishery biological data of Gonatopsis borealis,Sthenoteuthis oualaniensis,Berryteuthis magister shevtsovi and Todarodes pacificus were measured,and the pigmentation stage of beak were classified.Through covariance analysis,we studied whether there were gender differences in pigmentation stage.By analyzing the pigmentation characteristics of beak,the relationship between pigmentation stage of beak and mantle length,body weight,sexual maturity and the external morphological parameters of beaks was established.The artificial neural network was used to analyze the contribution rate of each growth factor to pigmentation of beak of different cephalopods.By comparing the characteristics of pigmentation in beak of cephalopods in four different seas,the differences of pigmentation in beak were preliminarily discussed.The results are as follows:(1)There were no significant difference between sexes in the relationship between pigmentation of beak and mantle length,body weight and sexual maturity for Gonatopsis borealis in the northern northwest Pacific Ocean.There was a positive correlation between pigmentation stage and mantle length,body weight,sexual maturity and the external morphological parameters of beaks,which generally increased gradually with the growth of individuals.The results showed that the lower rostrum length,sexual maturity,lower hood length and lower wing length contributed a lot to pigmentation,accounting for 22.70%,21.80%,16.00%and 11.8%respectively.(2)There were significant differences between sexes in the relationship between pigmentation of beak and mantle length,body weight and sexual maturity for Sthenoteuthis oualaniensis in northwest Indian Ocean.There was a positive correlation between pigmentation stage and mantle length,body weight,sexual maturity and the external morphological parameters of beaks,which generally increased gradually with the growth of individuals.Generally speaking,the deposition rate of female individuals is faster than that of male individuals.The results showed that sexual maturity,mantle length,lower wing length and body weight contributed significantly to pigmentation stage,accounting for 29.4%,14.4%,13.6%and 12.9%respectively.(3)There were significant differences between sexes in the relationship between pigmentation of beak and mantle length,body weight and sexual maturity for Todarodes pacificus in East China Sea Pacific Ocean.There was a positive correlation between pigmentation stage and mantle length,body weight,sexual maturity and the external morphological parameters of beaks,which generally increases gradually with the growth of individuals.Except for the lower rostrum length,the pigmentation stage of beak of female individuals increases faster than that of male individuals with its shape parameters.The results showed that the the lower wing length,lower rostrum length,lower hood length,mantle length contributed significantly to pigmentation,accounting for 27.20%,18.50%,15.60%and 14.10%respectively.(4)Pigmentation stage of beak of Gonatidae and Ommastrephidae were positively correlated with mantle length,body weight and the external morphological parameters of beak,and increased with the sexual maturity.The R~2between pigmentation stage and mantle length is greater than that between pigmentation stage and body weight.The pigmentation stage of beak of Gonatopsis borealis and Todarodes pacificus in immature and mature stage is higher than that of Sthenoteuthis oualaniensis.Among the samples of Gonatidae,the fitting effect of the lower hood length,the lower rostrum length and the lower wing length on pigmentation stage of beak were good.Among the samples of Ommastrephidae,the fitting effect of the lower lateral wall length on pigmentation stage of beak was better.The lower hood length and the sexual maturity of Gonatidae contributed a lot to the pigmentation stage of the beak.The lower wing length and the sexual maturity of Ommastrephidae contributed a lot to the pigmentation stage of the beak.