Genetic Variation And Phylogenesis Of The Cuttlefishes In The Waters Of China

Phenotypic variation was researched in four populations of Sepiellamaindroni de Rochebrune, 1884.collected from the coastal waters of SouthChina by observing and measuring softbody as well as hard structuresincluding upper beaks and radula. Results indicated that the formula of armswere inconsistent among the 4 samples, with the samples from Putian (PT)as 2<1<3<4 as well as Nan'ao (NA) and Shenzhen (SZ) being the same as2<3<1<4, while that of Zhanjiang (ZJ) being 1<2<3<4. Radula of PT, NAand ZJ samples was observed based on scanning electron microscopy. Theradula consisted of 7 longitudinal rows of teeth: a median tooth and the 1^st,2^nd, and 3^rd lateral or lateral, inner marginal, and outer marginal teeth. Amarginal plate was absent. The formula of radula was: 3 · 1 · 3. There wasno difference among the PT, NA and ZJ samples.The radula of nine dibranchiate cephalopods was compared on thebasis of scanning electron microscopic observation and morphologicalmeasurements. Results indicated that all of them consisted of 7 longitudinalrows of teeth. The formula of radula was: 3 · 1 · 3. Sepioidea (Sepia robsoni,S. esculenta, S. pharaonis, S. latimanus, S. aculeate, Sepiella maindroni,Euprymna berryi) had only one cusp in the median tooth and no marginalplates;but Octopus variabilis and O.ocellatus had 3-5 cusps, and themarginal plates were present. We also illustrated there were other differencein the radular structure among the nine species. The relationship of radula ofthe cuttlefishes, octopuses and squids were discussed. And we suggestedthat radula should be thought in the cuttlefish taxonomy.Screening of 46 putative enzyme-coding loci and 4 different kinds oftissues of Sepiella maindroni for enzymatic activities using starch gelelectrophoretic technique proved that 21 enzymes such as AAT, AK, ALP,AP, CK, DIA, EST, FBP, G3PDH, GPI, GRS, IDH, LDH, MDH, MEP, MPI,NP, PGDH, PGM, SOD and XO, were active to S. maindroni after beingstained. The tissue exhibiting stable and clear bands was also determined. Inall of the tissues used, mantle muscle tissue was the best for electrophoreticsurvey of isozymes. Buccal bulb muscle, eye and liver were fairly good forsome special enzymes, such as DIA, EST, MPI, NP, etc.Allozymic electrophoresis was used to investigate the genetic variationin 5 populations of the common Chinese cuttlefish Sepiella maindroni,distributed in the water of Japan, East China Sea and South China Sea,respectively. Samples were routinely examined at 14 enzymes comprising23 putative allozyme loci. The result revealed moderate levers of geneticvariability, with the proportion of polymorphic loci, P=0.1390.95, 0.2260.99,average observed heterozygosities per locus=0.038, average expectedheterozygosity per locus=0.039, and the effective number of alleles Ne, withvalues of 1.26. Nei's mean genetic distance (D) and identities (I) rangedfrom 0.0001 to 0.0018 and 0.9999 to 0.9987.Sequence of cytochrome oxidase subunit I (COI) gene was used toinvestigate the genetic variation in 5 populations of the common Chinesecuttlefish Sepiella maindroni in the waters of China and Japan. Part of COIgene was amplified with the polymerase chain reaction (PCR) andsequenced for 27 individuals, six from Nagasaki (NG), five from PT in EastChina Sea, and three other samples in South China Sea (five from each of 2samples collected off NA and SZ, six from ZJ). Resultant sequence datashowed that there were eleven variable nucleotide positions in the 661base-pair segments of the gene and that all 27 sequences were grouped into9 haplotypes (A-I). No marked genetic difference was observed amongthose populations.Part of the 16S rRNA gene was amplified with PCR and sequenced for29 individuals, five from NG, six from PT, and six from each of the threesamples collected off NA, SZ and ZJ. The result showed that a total of 5nucleotide positions were found to have gaps or insert of base pairs amongthese individuals, and thirteen positions were examined to be variable in allthe sequences, which ranged from four hundred ninety four to five hundrednine base pairs. All of the individuals were grouped into seven haplotypes(from A to G). No marked genetic difference was observed among thosepopulations. All of the individuals from Nagasaki belonged to haplotype Aand haplotype C were found only in the coastal waters of China. It wassuggested that haplotype C could be taken as a kind of genetic marker toidentify the populations distributed in the water of Japan and East-SouthChina Sea.Phylogenetic relationships for extant cephalopods have been basedmainly on morphology and paleontology. Nucleotide sequence data fromCOI gene and partial 16S rRNA gene were used as an alternative molecularapproach to morphology and can provide valuable information ontaxonomic relationships at the infra-familial and much higher level. Severalphylogenetic trees were built by the Maximum likelihood,Neighbour-Joining and parsimony methods. The coleoids were obviouslydivided into two main lineages, Octopoda and Decapoda (Sepioidea +Teuthoidea). The order Sepioidea, including the Sepiidae, Sepiolidae andIdiosepiidae, was not supported by molecular evidence. Sepiolids wereclearly excluded from the order. Sepiella (Sepiella maindroni) and Sepia(including 5 species) could not have visible boundary line based on COIgene data. The reason was explained. Both of the data of 16S rRNA andamino acid of COI can distinguish both of the genera (Sepiella and Sepia).The COI and 16S rRNA genes of cephalopods were a prevalent tool toanalyze taxonomic relationships.