AUTHOR=Gong Lin , Yang Mei , Janussen Dorte , Dohrmann Martin , Li Xinzheng 

TITLE=A new species of Caulophacus (Hexactinellida: Lyssacinosida: Rossellidae) from the western Pacific Ocean, with new insights into the mitochondrial genome characteristics of hexactinellid sponges

JOURNAL=Frontiers in Marine Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.979912

DOI=10.3389/fmars.2023.979912

ISSN=2296-7745

ABSTRACT=<p>A new species, belonging to the rossellid subfamily Lanuginellinae Gray, 1872, is described based on two specimens collected from two different seamounts in the western Pacific Ocean. Species characterization was approached by analyzing the morphological and skeletal features as well as the complete mitochondrial genome. <italic>Caulophacus</italic> (<italic>Caulodiscus</italic>) <italic>iocasicus</italic> sp. nov. is distinguishable from its congeners by its branched external shape and a unique combination of microscleres. It only has hemionychohexasters while other <italic>C</italic>. (<italic>Caulodiscus</italic>) species additionally have either onychohexasters or discohexasters. Furthermore, the new species has microhexactins, which have not been reported from the other six species of <italic>C</italic>. (<italic>Caulodiscus</italic>). Regarding the mitochondrial genome, the occurrence of the <italic>atp8</italic> gene, the absence of <italic>tRNA <sup>E</sup></italic>, the translocation of <italic>tRNA <sup>D</sup></italic> between <italic>cob</italic> and <italic>nad6</italic>, and the rearrangement of <italic>nad6</italic>-<italic>nad4</italic> distinguish the new species from other rossellids and even other hexactinellids for which mitogenomic information is available. The herein revised morphological and molecular information of the genus <italic>Caulophacus</italic> also suggests that the monospecific subgenus <italic>C.</italic> (<italic>Caulophacella</italic>) should be removed from <italic>Caulophacus</italic> and reinstated as a separate genus in the subfamily Lanuginellinae.</p>