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

Abstract

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. Caulophacus (Caulodiscus) iocasicus sp. nov. is distinguishable from its congeners by its branched external shape and a unique combination of microscleres. It only has hemionychohexasters while other C. (Caulodiscus) species additionally have either onychohexasters or discohexasters. Furthermore, the new species has microhexactins, which have not been reported from the other six species of C. (Caulodiscus). Regarding the mitochondrial genome, the occurrence of the atp8 gene, the absence of tRNA E, the translocation of tRNA D between cob and nad6, and the rearrangement of nad6-nad4 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 Caulophacus also suggests that the monospecific subgenus C. (Caulophacella) should be removed from Caulophacus and reinstated as a separate genus in the subfamily Lanuginellinae.

Expanded sampling of New Zealand glass sponges (Porifera: Hexactinellida) provides new insights into biodiversity, chemodiversity, and phylogeny of the class

“…More taxonomic work on the morphology of the poorly known Caulophacella and its relationship to Lophocalyx , as well as better taxon sampling of the latter (currently 12 described species) will be necessary to settle this issue. In any case, Caulophacella clearly groups outside Caulophacus , confirming its status as a separate genus ( Gong et al, 2023 ; contra Boury-Esnault et al, 2015 ). The other species (and new genus) of Lanuginellinae sampled during Sonne Cruise SO254 with several specimens (NIWA 126169 and four other samples; Table 1 ), despite having some similarities in spiculation to Sympagella (see above), the sister taxon to all remaining lanuginellines, clearly diverges after that genus in the molecular phylogeny and forms a distinct branch in the Lanuginellinae clade ( Fig.…”