Study On The Molecular Phylogeny Of Coastal Gunus Parapenaeopsis Based On Chineses Species And The Classification Status Of Close Species

Seven species of the Genus Parapenaeopsis (Crustacea, Decapoda) have been recorded from China coastal seas,while 19 identified species were reported in the Indo-West Pacific Region. All of these species are of economic importance in local fisheries production. Some of them, such as Parapenaeopsis hardwickii (Miers, 1878) in the East China Sea and the South China Sea, are high-yield resources. The long-standing question existed in marine crustacean resources study is whether Parapenaeopsis hardwickii (Miers, 1878) and the closely related species Parapenaeopsis cultrirostris(Alcock,1906)are two distinct valid species or the same species. Liu & Wang (1987) and Liu et al.(1988) recorded both of them as distinctive valid species, but recently they suggested that Parapenaeopsis cultrirostris Alcock should be the synonym of Parapenaeopsis hardwickii(Miers). The rostrum of the latter male is sexual dimorphic, being long sigmoid styliferus in the young stage but changing into short dagger shaped after maturation ecdysis. This needs further confirmation. Liu and Wang (1987) recognized 2 new species, which were morphologically similar to P. cornuta (Kishinouye, 1900), and were named as P. sinica Liu et Wang and P. incisa Wang et Liu in 1987. Although the 3 species are distinguished on morphological characters, they are very similar and usually be confused. So, the distinction and validity of the two species still needs more strong evidences. The present study utilized the method of sequences (16S rRNA,cytochrome C gene )comparisons to testify the validity of the 2 close species groups . Alignment of the sequences of the 16S rRNA and COI gene was used to reconstruct phylogenetic tree and to infer phylogenetic relationship of the 7 Chinese species. The molecular phylogenetic study results are as fellow: (1)There is only one species between P. hardwickii and P. cultrirostris in Chinese specimens. Parapenaeopsis cultrirostris Alcock is the synonym of Parapenaeopsis hardwickii Miers. The rostra of the latter males are sexal dimorphic. (2) P. sinica, P. cornuta and P. incise are 3 valid closely related species. The phylogenetic relationship between P. cornuta and P. incise is closer, and the molecular phylogenetic study result doesn't stand for the suspicion of the 2 species' validity. (3) The dendrograms of the 6 shrimps reveal that there is apparent deficiency in analysis of the phylogenic relationship in Genus Parapenaeopsis just by the sequences of 16S rDNA and COI gene. (I) 16S rDNA is fitter to analyze the relationship among closely relative species. The genetic marks such as 18S rDNA or 28S rDNA should be also analyzed in order to reveal the relationship among distantly relative species. (II) The difference of the base substitution pattern among the 3 kinds of codes of COI gene is remarkable, and the COI gene fragment in our study is rather short. So, it's difficult to use COI gene to reconstruct good dendrograms which can successfully reveal the phylogenic relationship. Thus the longer fragment such as cyt b gene is more suitable to farther study on the phylogenic relationship in Genus Parapenaeopsis.