Study On The Microstructure Of Eyestalk Of Several Economical Shrimps And Crabs

Portunus trituberculatus,Eriocheir sinensis,Penaeus orientalis and Procambarus clarkii are all major economic shrimps and crabs in China.Age identification is the basis for research on fishery resources and fishery management.However,there is no accurate and effective method for age indentification of crustaceans.The analysis of calcified structures to study the age and growth of crustaceans is still a blank in our country.Most of the study focus on the relationship of growth bands and age.In addition to this,the pretreatment method and grinding method for the eyestalks and gastric mills is uncertain which the most proper method is.In this study,we compare different pretreatment methods and grinding section.To select the most proper method and section.Afterward,we develop a method to research the relationship of growth increments and carapace length?CL?and carapace width?CW?and weight of these shrimps and crabs.This paper also periodically conducts a periodic verification of growth increment and proposes corresponding hypotheses.This paper provides usable methods and foundation for future research,and some ideas for future researchers in the age identification of crustaceans.The samples of 148 Portunus trituberculatus,42 Eriocheir sinensis,69 Penaeus orientalis and 180 Procambarus clarkii are studied in this paper.We observed the microstructure of eyestalk of four species of shrimps and crabs,and preliminary studied the relationship between the growth bands and their basic biological characteristics.The main conclusions of the study are as follows :?1?The most appropriate research method is selected according to the type of crustacean to be studied and the desired effect,when selecting the method for grinding the eyestalk.Before cleaning the crab's eyestalk,it is not suitable for boiling.After the inside of the eyestalk is clean,it can stand directly in the embedding box,when grinding the hard-shelled species' eyestalk.However,for the soft-shelled species eyestalk,the eyestalk should be cut first,carefully removing the organic matter attached to theeyestalk.And when grinding,you should be more cautious.For the grinding of the eyestalk of the Portunus trituberculatus,it is easier to observe the growth increments of in the horizontal grinding,and it is easier to observe the growth bands in the vertical grinding.?2?The eyestalk of Portunus trituberculatus,Eriocheir sinensis,Penaeus orientalis and Procambarus clarkii are divided into 4 layers: the epicuticle,exocuticle,endocuticle,and the membranous layer.The width of the growth increments of the eyestalks of Portunus trituberculatus,Eriocheir sinensis and Penaeus orientalis has narrow-wide-narrow fluctuation from the junction of the exocuticle and endocuticle to the junction of the endocuticle and the membranous layer.The width of growth increments near the edge of endocuticle is small,and the width of growth increments of the middle part of endocuticle is large.However,The width of the growth increments of the eyestalks of Procambarus clarkii has wide-narrow fluctuation.The order of the width of the growth increments of the four species of shrimps and crabs is: Procambarus clarkii > Eriocheir sinensis > Portunus trituberculatus > Penaeus orientalis.The variation and size of width of growth increments are positively related to the change and size of the growth rate of the species.?3?In this study,the linear relationship between the carapace length?CL?and the carapace width?CW?of Portunus trituberculatus and Eriocheir sinensis was found to be: Male Portunus trituberculatus :LCW=2.069×LCL+2.004?R₂=0.945?Female Portunus trituberculatus:LCW=1.988×LCL+2.121?R₂=0.961?Eriocheir sinensis:LCW=1.147×LCL-1.167?R₂=0.998?The body weights of Portunus trituberculatus and Eriocheir sinensis increased with the length of the carapace length and the carapace width.The carapace width and their weights showed a power function.The relations is: Male Portunus trituberculatus:W=0.00003×LCW^3.14991?R₂=0.875?Female Portunus trituberculatus:W=0.00003×LCW^3.08819?R₂=0.978?Eriocheir sinensis:W=0.0006×LCW^2.947?R₂=0.9839?The length?L?and weight?W?of Penaeus orientalis and Procambarus clarkii are power functions.The relationship is:Penaeus orientalis:W=0.00002×L2.718?R₂=0.866?Procambarus clarkii:W=6×10-11×L5.792?R₂=0.820??4?Relationship between the numbers of growth increment and CL.According to the minimum AIC rule,The number of growth increment and carapace length of male Portunus trituberculatus showed a logarithmic function.The relations is: LCL=27.812 × LN?t?-59.431?R₂=0.591?.The number of growth increment and carapace width of male Portunus trituberculatus showed a Logistic function.The relations is: LCW= 108.459/1+e-0.130×?t-23.341??R₂=0.634?.The number of growth increment and weight of male Portunus trituberculatus showed a logarithmic function.The relations is: W=72.345×LN?t?-219.994?R₂=0.583?.The number of growth increment and carapace length of female Portunus trituberculatus showed a Gompertz function.The relations is: LCL=28.561×e-0.0515?t-23.856??R₂=0.781?.The number of growth increment and carapace width of female Portunus trituberculatus showed a Gompertz function.The relations is: LCW=58.296×e-0.0493?t-23.693??R₂=0.778?.The number of growth increment and weight of female Portunus trituberculatus showed a logarithmic function.The relations is: W=155.137×LN?t?-503.955?R₂=0.711?.There is a linear correlation between the number of growth bands and molting times of Portunus trituberculatus.The relations is: M=1.055s-0.812?R₂=0.610??The number of growth increment and carapace length of Eriocheir sinensis showed a Logistic function.The relations is: LCL=61.53/1+e-0.066×?t-42.59??R₂=0.969?.The number of growth increment and carapace width of Eriocheir sinensis showed a Logistic function.The relations is: LCW=70.01/1+e-0.063×?t-44.49??R₂=0.971?.The number of growth increment and weight of Eriocheir sinensis showed a Gompertz function.The relations is: W=55.14×e-0.080?t-47.89??R₂=0.895?.The number of growth increment and length of Penaeus orientalis showed a Logistic function.The relations is: L=333.84/1+e-0.04?t-39.46??R₂=0.747?.The number of growth increment and weight of Penaeus orientalis showed a Logistic function.The relations is: W=92.74/1+e-0.09?t-58.11??R₂=0.623?.The number of growth increment and length of Procambarus clarkii showed a Logistic function.The relations is: L=96.66/1+e-0.25?t-2.54??R₂=0.461?.The number of growth increment and weight of Procambarus clarkii showed a Logistic function.The relations is: W=22.48/1+e-0.41?t-11.78??R₂=0.454?.The relationship between the number of growth increment and the CL,CW,and weight was both fast in the early stage and slow in the late stage,which was consistent with the growth pattern.The growth rate of the number of growth increment is consistent with the growth rate of Portunus trituberculatus and Eriocheir sinensis,and gradually slows down with time.The numbers of growth bands are the same as the molting times.The changes in the relationship between the number of growth increment and length and weight are consistent with changes in their growth rates.The number of growth bands of eyestalk of Penaeus orientalis is related to its age.1 age corresponds to 1 growth band.The formation of a growth increment requires 9.9 to 14.6?12.3±1.5?days.No growth band was found inside the eyestalk of Procambarus clarkii.