Evolutionary analyses of phylum Chaetognatha based on mitochondrial cytochrome oxidase I gene

Authors : Sam PETER, Manoj Kumar Bhaskaran NAİR, Devika PİLLAİ

Pages : 508-518

View : 9 | Download : 2

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Chaetognaths insert ignore into journalissuearticles values(arrow worms); are an enigmatic group of transparent planktonic invertebrates and play an important role in the marine food web. Their morphological and developmental features have raised extensive debates since the discovery of the phylum in the 18th century. Uncertainty in the phylogenetic placement of certain chaetognath species still exists and is puzzling many scientists who have tried to clarify this task. Studies using a portion of both small subunit ribosomal ribonucleic acid insert ignore into journalissuearticles values(SSU rRNA); and large subunit ribosomal ribonucleic acid insert ignore into journalissuearticles values(LSU rRNA); genes when integrated with conventional taxonomy were contributed to resolve taxonomical issues in this group. Here we present the first phylogenetic study of Chaetognatha based on a portion of mitochondrial cytochrome oxidase I insert ignore into journalissuearticles values(COI); gene and compare our results with the earlier morphological and molecular evolutionary hypotheses. This study includes 16 extant species, representing 8 genera and 6 of which are among the 9 extant families. We recommend the following clade structure for the phylum: Aphragmophora comprising Sagittidae with Pterosagittidae and Krohnittidae included in the Sagittidae and Phragmophora comprising Eukrohniidae, Spadellidae, and Heterokrohniidae. Phylogenetic analyses also supported the division of Phragmophora into two monophyletic groups: the Monophragmophora and Biphragmophora. Moreover, Ctenodontina/Flabellodontina and Syngonata/Chorismogonata suborders were not validated. Precise phylogenetic investigations using various molecular markers and specimens from diverse regions are definitely needed to provide an exact evolutionary concept on this phylum.
Keywords : Chaetognatha, evolution, phylogenetic analysis, mitochondrial cytochrome oxidase I gene, Bayesian inference, maximum likelihood