The Establishment Of Classification System Based On Beak Of Common Cephalopod In The South China Sea

In the coastal waters of South China Sea,there are complexity of fauna composition and diversity of species in cephalopod.The cephalopod fishery has the important position in the coastal marine fisheries.As a feeding organ of cephalopods,beak is a good material for classification and identification,which has the characteristics of stable structure and corrosion resistance.As an important source of human animal protein,cephalopod also occupies an important position in the marine ecological system.It is usually an important food of tuna,whale and other large marine fishes and mammals.Beak usually remained in its stomach because of difficult to digest.Therefore,the establishment of the classification system based on beak is helpful to understand the position and function of cephalopod in the marine ecosystem,and to ensure the sustainable utilization of the resources.To this end,in this study the beaks of six common species in the South China Sea' coastal waters are used as studying object.We will combine with morphology,beak growth characteristics,morphological parameters and individual growth of the basic characteristics,selected from the stability index growth,and establish species classification system and search table based on beak for common cephalopod in the South China Sea,which will provide the basic data for fishery biology research of Cephalopod in the South China sea.The main results are as follows:(1)Fishery biology characteristics of common Cephalopod.In six species of cephalopod,with Uroteuthis chinensis samples,the range of 70-395 mm,the average carcass length is 188.6mm,and the dominant group is 85-155 mm.The body weight range from 22 to 637 g,the average is 139.6g,and the advantage of body weight group is 45-90 g.The mantle length and body weight of different species have significant differences(P<0.05).The relationship for mantle length and body weight of Uroteuthis chinensis,Loliolus sumatrensis,Sthenoteuthis oualaniensis and Octopus ocellatus expressed by power function,Loligo duvauceli,Octopus membranaceus from mantle length exponential function relation with body weight.In stage ? for mature standards,other species removing Octopus membranaceus outside,most of the individuals in the immature stage,Octopus membranaceus samples to stage ?,all samples were not found in stage ?.In addition to other species of Sthenoteuthis oualaniensis in the stomach fullness level to 0 and 1,basically in a state of empty stomach,Sthenoteuthis oualaniensis sample with 1 and 2 grade.(2)Morphological characteristics and morphological parameters of beak.To beak of Uroteuthis chinensis for example,upper beak tip length,edge pigmentation,jaw angle is smaller,shorter.The whole wing extends downward,the side wall has a shallow direction after the degree of depression.The head of beak is very long,and the front part of the pigmentation is obvious,in the back-end transparent state.The lower beak is similar with upper beak,there exist obvious differences in structure,short and sharp beak slip,pigmentation,jaw angle close to 90 degrees.The wing is long,the side wall of a parallelogram,skull short front pigmentation obviously.The analysis of six species of cephalopods showed that there were significant differences in the morphological characteristics of different species of beak.Beak can distinguish well between different species in orders(Teuthoidea,Octopoda)and families(Loliginidae,Ommastrephidae,Octopodidae),can be used as one of the basis for classification of cephalopods.The upper beak of each species is generally longer than lower beak.The length of hood and crest in upper beak is larger than lower beak,while upper wing length is smaller.(3)Study on growth characteristics of beak.Principal component analysis showed that upper hood length,upper crest length,and lower lateral wall length of beak could be used as the index of the morphological parameters of the beak.The morphological parameters of different species are obviously different of six species of cephalopods.These characteristic morphological parameters respectively with mantle length and body weight of the growth equation,species of Loliginidae,beak shape parameters and mantle length has a significant linear relation(P<0.01),the exponential function relationship significantly with body weight(P<0.01).There were same results in Ommastrephidae and Loliginidae,the beak shape parameters and mantle length and body weight were significantly linear relationship,exponential relationship(P<0.01).Species of Octopodidae,the morphological parameters of beak and mantle length and body weight showed significant power function relationship(P<0.01).(4)Selection of stability index and classification index of beak morphological parameters.The analysis of beak morphological parameters ratio of six species of cephalopod showed that various species of beak have stable parameters ratio,and not changed with the growth of individual changes in mantle length and body weight.In order to Uroteuthis chinensis as an example,the beak morphological parameters of proportion index with the individual growth and development is relatively stable state,include URL/UHL,URL/UCL,URL/ULWL,UWL/UCL,UWL/ULWL,UHL/UCL,ULWL/UCL,LRL/LCL,LRL/LLWL,LRL/LWL,LWL/LCL and LWL/LLWL.There are some differences between the stable parameters of different species beak,can be classified on the basis of family,genus and species.(5)Cephalopod classification system based on beak.Firstly,we can find the difference of Teuthoidea and Octopoda,Loliginidae and Ommastrephidae and distinguish them according to the morphological characteristics of beak.Secondly,we can distinguish different species according to the difference of morphological parameters of beak stability index.Based on the above results,we established a classification table of common cephalopod in the South China Sea.