||The genus Petrolisthes is the largest, the most widely distributed genus in the family Porcellanidae. It contains over 100 species distributed around the world , including over 16 species commonly found near the shore of Taiwan . We discuss the diversity and phylogeny of them, and the similarities and dissimilarites of between the molecular biology and traditional morphology.|
We got 15 pocerlain crabs specimen and almost 900bp and 800bp of them in the 16S rRNA and 12SrRNA of MtDNA respectively. The average pairwise distances is 0.2510 and 0.2249, and the phylogenetic relationship can be determined by observing the morphology of the Petrolisthes crabs, especially the number of spines on the anterior margin of the carpus of the chelipeds, which are an important basis for evolution and classfication.
The tree is made from the morphological characters is put more weight by us to the numbers of spines on the anterior margin of the carpus of the chelipeds, and the presence or not of the spines of the outline of the chelipeds. And we can get the same resuit as the molecular phylogenetical tree. This provides an evidence to the situation that molecular phylogeny will present to the morphological character, and some of the characters are more important to the molecular evolution.
The phylogeny relationship of porcelain crabs of the west and east Pacific don’t be separated by the Pacific. But the primary phylogenetic relationship still present to the morphological characters. The group T is some species that evolve rapidly with the environment at the later evolution phase.
The mitochondrial DNA of Petrolisthes has been sequencing two third of all and compared with the 5 previously studied species （Limulus polyphemus、Artemia franciscana、Daphnia pulex、Penaeus mondon、Pagurus longicarpus）in the class Crustacean. The results reveal that the genome of Petrolisthes is arranged most like that of the hermit crab Pagurus, suggesting they may share an ancestral phenotype. However, the start and terminal codon of Petrolisthes show a unusual similarity to that of Penaeus, the phylogenetic result of the sequence of the protein coding genes support the classification to the anomura conclude the Pagurus and Petrolisthes, and there are high bootstrap values more than 84 with the clade of Pagurus and Petrolisthes in the neighbor-joining method tree and maximum parsimony tree. These analysis showed encourage much needed research and discussion about the relationship between anomura, brachyura and macrura, of the order Decapoda.