Phylogeny of sea cucumber (Echinodermata: Holothuroidea) as inferred from 16S Mitochondrial rRNA gene sequences

Abstract

This study aimed to determine phylogenetic relationship between and among selected species of sea cucumbers 
\n(Echinodermata: Holothuroidea) using 16S mitochondrial ribosomal RNA (rRNA) gene. Phylogenetic analyses of 37 
\npartial sequences of 16S mitochondrial rRNA gene using three main methods namely neighbour joining (NJ), maximum 
\nparsimony (MP) and maximum likelihood (ML) showed the presence of five main genera of sea cucumbers: Molpadia 
\nfrom order Molpadiida and four genera of order Aspidochirotida namely Holothuria, Stichopus, Bohadschia and 
\nActinopyga. All of the 17 species obtained from Malaysia distributed among the main genera except within Actinopyga. 
\nInterestingly, Holothuria excellens was out of Holothuria group causing Holothuria to be paraphyletic. High bootstrap 
\nvalue and consistent clustering made Molpadia, Stichopus, Bohadschia and Actinopyga monophyletic. The relationship 
\nof Actinopyga with the other genera was unclarified and Stichopus was sister to Molpadia. The latter finding caused 
\nthe resolution at order level unclear. The pairwise genetic distance calculated using Kimura 2-parameter model further 
\nsupported and verified findings from the phylogenetic trees. Further studies with more samples and different mitochondrial 
\nDNA genes need to be done to get a better view and verification on the molecular phylogeny of sea cucumbers