Phylogenetic variation of marine sponges (Porifera: Demospongiae) surrounding Con Co Island of Vietnam employing 28S rRNA gene fragments

Demosponges are the most divergent of all current known marine sponges. In Vietnam, knowledge on their phylogenetic information still limited, although it is important for sustainable conservation of these lowest metazoans. In this study, the phylogenetic variation of 13 demosponges (named CC4-CC49) collected from Con Co Island in the Central Vietnam was elucidated based on polymorphism in DNA sequences of D1 (346 bp) and D3-D5 (637 bp) fragments on their 28S ribosome RNA gene. Phylogenetic Neighbour Joining trees of both sequence data sets revealed that 13 studied samples were clustered into 5 lineages belonging to 6 families of 4 orders in class Demospongiae with strong confidence intervals (87-100%), reflecting their high phylogenetic variation. 49 and 88 specific substitutions among lineages and particular character sets for each lineage were observed when aligned D1 and D3-D5 fragments of the taxa in each lineage, interpreting significant genetic distance between the 5 lineages. High homology when in-pair aligned each sequence set of the studied and referred demosponges inferred 13 current samples to be 7 different taxa as previously identified based on morphological characters, indicating the congruence between morphometry and current molecular employment in identification of these samples. Molecular approach in this study could be applied for further research on genetic diversity including phylogenetic divergence of sponges in other regions of Vietnam.