A Morphology Classification And Phylogenetic Analysis Of Three Species Of The Scleractinian Coral Genus Goniopora

The skeletons of scleractinian corals are easily affected by environmental factors,and the external morphology of some species is highly similar,which is difficult to distinguish.In this study,three species of Goniopora with similar appearance were taken as the experimental objects,and their morphology,tissue sections,density and species of symbiodinium,morphology of nematocysts and other parameters were compared and analyzed,in order to find more auxiliary identification features to classify them more accurately and find out more accurate classification standards.At the same time,using high-throughput sequencing technology,the mitochondrial genomes and comparative transcriptomes of three species of Goniopora were obtained and analyzed to explore their evolutionary relationship and the internal reasons for the color differences of appearance.The main reserach results are as follows:1.The morphological characteristics and identification result of three species of Goniopora are as follows:(1)Macromorphology: There were some differences in the number of septals and the diameter of calices among the three species of Goniopora:The diameter of calices of G.lobata is 3.32 ± 0.06 mm,the number of septals were21.71 ± 2.36;the diameter of calices of G.planulata is 4.80 ± 0.4 mm,the number of septals were 21.10 ± 1.8;the diameter of calices of G.norfolkensis is 3.20 ± 0.63 mm,the number of septals were 14 ± 2.81.(2)Micromorphology: The shape of septal teeth of three species of Goniopora were symmetrical,gentle,curved;the number of septal teeth of G.norfolkensis was the most,G.planuata was the least,and G.norfolkensis has no granule.(3)There was no significant difference among the three tissue sections.(4)There was no significant difference in the composition of symbiodinium among three species of Goniopora;G.norfolkensis has the highest density of symbiodinium,followed by G.planulata,and G.lobata has the lowest density of symbiodinium.(5)The morphology of nematocysts: G.planulata has the longest nematocysts,followed by G.norfolkensis,and G.lobata has the shortest nematocysts;there was no significant difference in the width of cnidocyst among three species of Goniopora;the length of cnidocyst of is significantly shorter than G.planulata and G.norfolkensis.2.The result of mitochondrial sequencing: The whole mitochondrial genome of G.planulata was completely consistent with G.norfolkensis,the total length was 18,766 bp,GC content is 37.2%.The proportions of base A,C,G and T were 25.6%,13.7%,23.5%,37.2%.Based on mitochondrial genomes of 20 species of Scleractinia corals to constructed a phylogenetic tree showed that,G.planulata has a close relationship with G.columna,with a remote relationship with G.lobata.3.Single copy homologous gene analysis based on comparative transcriptome showed that,G.lobata has close relationship with G.norfolkensis.Using the annotation information of comparative transcriptome,the realtime-q RCR result showed that green fluorescent protein gene expression was significantly higher than purple-blue nonfluorescent chromoprotein expression in G.lobata with green color;while in G.planulata and G.norfolkensis,purple-blue non-fluorescent chromoprotein expression was significantly higher than green fluorescent protein gene expression.