| The Echinothurioida belongs to Echinoidea,Echinoidea.Echinothurioida is 60 species of 11 genera and 3 families.Echinodermata is the only deuterostomes in Invertebrates and has a high evolutionary position in Invertebrates.The Echinothurioida is a special kind of sea urchins with very poor records of fossil species.The Echinothurioida shells are soft and can sometimes be moved on soft deep-sea sediments large hoof-shaped spines.It is distributed in the global sea area and in the deep sea of shallow sea.It is easy to distinguish from other sea urchins because of its soft cortical shell and thin overlapping bone plates.Anderson found a large number of new species in a 2013 and 2016 study of Echinothurioida in New Zealand and southeastern Australia,suggesting that the global diversity of Echinothurioida is not yet fully understood.And because of the dark,high pressure,hypoxia and oligotrophic characteristics of the deep sea,is a natural extreme environment.Seamount is a unique habitat in the ocean.However,due to the influence of sampling methods,the understanding of Echinothurioida form the seamounts of western Pacific is insufficient.In this paper,the marine research Institute of Oceanology of the Chinese Academy of Sciences has been studying the specimens of the Echinothuriidae and Phormosomatidae collected from Magellan mountain area,Jiaolonghai mountain area,Yapu sea mountain area,Mariana sea mountain area and Caroline sea mountain area in the since 2014.By means of traditional morphology and scanning electron microscopy,identification were carried out on the species of Echinothuriidae and Phormosomatidae distributed in the Western Pacific Seamounts.The phylogeny of the Echinothurioida has been studied by molecular biotechnology.In addition,the geographical distribution of the species in the Echinothuriidae and Phormosomatidae were also studied.1)A total of 4 genera and 9 species were described.Among them,5 species were new to science(Araeosoma sp.1,Araeosoma sp.2,Araeosoma sp.3,Araeosoma sp.4 and Hygrosom sp.1)and a new record Phormosoma placenta Thomson,1872.The morphological characteristics and distribution of all the species were described,the classification and retrieval table of the Araeosoma was compiled.2)The genetic distance spacing based on COI gene sequence was constructed,and the genetic distance spacing based on 16 S gene sequence was constructed..It is proved that the arrangement of the pore pair in the aboral side of the Tromikosom can not be used as an identification feature among species.Composed of the Tromikosom and Sperosoma.And the genetic distance of different genera of the genus Echinothurioida varies greatly.3)The phylogenetic tree of Echinothurioida was constructed.It is proved that the monophyletic development of the Echinothurioida.And families are non-monotonic development.Whether the difference between families can be regarded as the difference between departments or genera is open to question.Phormosoma and Sperosoma are more basic and developed to form sister branches,and Araeosoma is more evolved.4)The global distribution characteristics of Echinothuriidae and Phormosomatidae were reviewed,and the distribution characteristics of soft sea urchins in the Seamounts of Western Pacific were discussed with in situ camera data.Proving that the Pacific is a hotspot for biodiversity.All species in the Asthenosoma and Hapalosoma are completely distributed in shallow water depths of 1000 m.The Araeosoma is the dominant species in the western Pacific Ocean.Most of the Echinothurioida species have hard substrates,which may be related to the limitations of sampling.This study is helpful to understand the species composition and distribution characteristics of the Echinothuriidae and Phormosomatidae form the seamounts of western Pacific,to reveal the rich biodiversity form the seamounts of western Pacific,to enrich the gene sequence database and species information of the mountain sea creatures,to provide a reference for the hypothesis and geographical distribution of the distribution of seamount biodiversitys,and to provide basic information for the phylogenetic development of the deep Echinothurioida,which is of great significance to the exploration and utilization of deep sea biological resources and the protection of deep sea biodiversity in China. |
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