| In recent years,as a result of global warming and the deterioration of the marine environment,the coral reef ecosystem has deteriorated rapidly.Stony corals are the foundation of the coral reef ecosystem,in order to address the problem of coral reef degradation and restoration,it is necessary to study coral morphology and growth characteristics.In this paper,we studied one of the dominant coral species of Hainan Island,Galaxea fascicular is,focusing on the morphology and growth characteristics of the two types of Galaxea fascicularis,and the seasonal variation of their symbiotic zooxanthellae,explored the two types of clusters of microbasic p-mastigophores(MpM)shaped coral adaptation strategy differences,so as to provide theoretical support for coral reef protection.According to the nematocyst morphology,Galaxea fascicularis can be divided into two types:Hard(H)and Soft(S),and this morphological characteristics,is associated with a deletion of mitochondrial DNA over a period of 290 bp,S(Soft)contains the 290 bp(Long,denoted as SL),while H(Hard)does not(Short,denoted as HS).In the surrounding sea area of Hainan Island,the HS type and SL type coexisted and interlaced,and the proportion is roughly the same.The shape and appearance of type HS and SL are also different,the HS helmet is high and the tentacle is long,while the SL helmet is short,the tentacles are short and around the helmet cap.In addition,the preliminary study showed that the resistance of the two cluster corals to high temperature whitening was also significantly different,and the HS type was high temperature resistant and SL type was not resistant.This paper further reveals the differences in morphological structure and growth characteristics of these two types of clustered helm corals.The results are as follows:1.Morphological differentiation of two types of Galaxea fascicularisThrough the microscope and Image-Pro Plusn7.0c software on the tufted helmet shaped spines of coral cnidocyst(LS),width(WC),cystic sac(LC)measurement.S type of nematocyst capsule wide fat,its central spines ca.as long 1/2 and H capsule;type of nematocyst capsule slender,the central spine length is about S type and H type capsule long 1/3.nematocyst capsule length had no significant difference.According to the type of Hydra tentacle type MpM nematocyst clusters,helmet shaped coral can be divided into three types,namely H,S and M.Two types of cnidocyst proportion of type M is not equal to the number of the majority,close to the S type or S type and H type cnida.H type compared with S type nematocyst in spine length(LS),width(WC),sac thorn length/sac length ratio(LS/LC)and cystic sac width/length ratio(WC/LC)were significantly less than S(P<0.05).On Hainan Island around the different populations,spine length(LS),width(WC),cystic sac(LC),thorn length/sac length ratio(LS/LC)and cystic sac width/length ratio(WC/LC)were significantly different in different geographical position(P<0.05).However S type MpM of nematocyst size and shape is relatively stable,there was no significant difference between geographical groups(P>0.05).2.Comparison of the morphology,structure,hardness and composition of two types of Galaxea fascicularisThe height of the Galaxea fascicularis helmet cap is the distance from the top of the helmet to the surface of the coenosteum.The results showed that the height of helmet cap of type HS and SL was 6.34 ± 1.65 mm and 3.72 ± 1.22 mm,and the height of HS helmet was significantly higher than that of SL type(P<0.05).In the number of septa statistical process,it was found that the order of formation of septa was ? round(6 slices),? wheels(6 pieces,intersections between ? wheel spacers)and? wheels(12 pieces,between ? and ? wheel septum).Then the ? wheel septum(between 24 pieces,between the ? or ? separators and the ? wheel septum)and the ?wheel septum(between ? or ? or ? grade septum and ? wheel septum).The adult cup ? wheel septum will be full,and the ? wheel septum is not full.The development of the ? round septum,when the ? septum was not complete,was born,or two cases were regenerated after the whole ? wheel was released.The length of diaphragm was measured by electronic magnifier and MicroCaptureHD software.The results showed that the length of HS type ?,? and ? wheel spacers was significantly less than that of SL type(P<0.05).The diameter of the adult cup with 24 septum was measured,the HS type was 3.95 ± 0.93 mm,and the SL type was 3.27 ± 0.6 mm.There was no significant difference between the two groups(P>0.05).The correlations between the number of diaphragms and the circumference of two types of coral are:y = 1850.11+1850.74x,R2=0.593,p=0.The spacer number,helmet of larger diameter Changyue week long.In addition,the length of two types of first class septum is significantly related to the helmet diameter,and the relation is,y =8.67+0.1x,R2=0.9519,P=0.3.Comparison of growth and asexual reproduction of two types of Galaxea fascicularisThe marginal coenosarc part of the sample was damaged by segmentation.8 days after being cultured in the laboratory,it is observed that a young cup will be produced on the wound in the wound,similar to the callus.Based on the statistics of the number of new young cups(number/cm)on the edge length of the same culture time samples,we compared the repair and growth rate of two kinds of clustered corals.The results showed that the number of newly born young cups of type SL showed more than the HS type from the first week,and the statistical difference was significant(P<0.05)for 18 weeks in the laboratory culture.The location of young cup development of Galaxea fascicularis is mainly from the coenosteum(cd)area,and the second is in the adult cup's Cup root(pdl),the lateral wall(pd2)and the top(pd3).The order of growth is cd,pd1,pd2,pd3,while in the central region of the sample,it is produced mainly from the top of the adult cup(pd3).A statistical analysis of 16 samples from two groups of indoor breeding showed that the number of pd3 on the top of the helmet cap was significantly higher than that of the HS type in the unit area(cm2).It shows that the asexual reproduction of type SL is more active than the HS type.For natural population,the proportion of SL type young cup was higher than that of HS,but there was no significant difference(P>0.05).The proportion of SL type young cup in summer was significantly higher than that of young cup in winter(P<0.05),but there was no significant difference between HS type.4.Seasonal changes of symbiotic zooxanthellae in two types of Galaxea fascicularisClustered helmeted coral and zooxanthellae are mutually beneficial,and zooxanthellae photosynthesis can provide most of the coral's organic nutrients.The density of zooxanthellae was calculated by counting the count of blood cell count board,and the density of zooxanthellae and the calcium quality of helmet were analyzed.It was found that the greater the density of yellowish algae,the more calcium in helmet(P<0.01).The seasonal variation of the density of the zooxanthellae in Galaxea fascicularis was significantly higher in winter than in the summer(P<0.05).We compared the two types of zooxanthellae in Galaxea fascicularis,the results showed that the density of HS was higher than that of type SL,and there was a significant difference in winter(P<0.05).The RFLP method was used to identify the strains of zooxanthellae,and the three strains of HS and SL were found to be C,D and CD(the coexistence of C and D).The proportion of zooxanthellae in type HS individuals is CD>C>D,and the proportion of zooxanthellae in SL type is C>D = CD.Due to the high photosynthetic efficiency of C.zooxanthellae,D.zooxanthellae confers higher heat resistance to symbiotic helmet-shaped corals.Therefore,the rapid growth of SL type(the faster formation of callus)may be related to the more individual proportion of the C strains of zooxanthellae.Based on the morphology structure and growth characteristics of HS type and SL type Galaxea fascicularis,and the comparison of environmental adaptation strategies of two types of Galaxea fascicularis,we can infer that HS type Galaxea fascicularis might has higher temperature resistance and SL type might has faster growth rate.Our result here could provide a theoretical basis for the artificial reef corals adaptive evolution. |
PDF Full Text Request