Two New Species and One New Genus of Glass Sponges (Hexactinellida: Euplectellidae and Euretidae), From a Transect on a Seamount in the Northwestern Pacific Ocean

Abstract

Hexactinellid sponges often form structural habitats for other organisms and thus support high biodiversity. Two representative morphotypes of hexactinellid sponges were sampled by a remotely operated vehicle along a transect (depths of 2377–2758 m) on the Ko-Hakucho Guyot in the northwestern Pacific Ocean, both new to science. One new species, Flavovirens hemiglobus gen. et sp. nov., which is pedunculate and bears the main choanosomal spicules of diactins, is clearly attributed to the euplectellid subfamily Bolosominae. Its set of microscleres present (namely, predominating oxyhexasters and discasters, and rare discohexasters and staurodiscs) characterizes it as a new genus. The other new species, Chonelasma tyloscopulatum sp. nov., which is funnel in form without dichotomous branching tubes or lateral oscula and has firm body walls supported by a three-layered dictyonal framework, is clearly attributed to the euretid genus Chonelasma (subfamily Chonelasmatinae). Its presence of surface pentactins, two types of scopules, and both oxy- and disco-tipped hexasters or hemihexasters as common microscleres, characterizes it as a new species. The placements are also supported by molecular phylogenetic evidence from nuclear 18S rDNA and 28S rDNA, and mitochondrial 16S rDNA and cytochrome c oxidase subunit I (COI) gene. More sampling efforts should be conducted to improve the understanding of the biodiversity of deep-sea seamount sponges.

Teganium (Porifera, Hexactinellida) from the Middle Ordovician Castle Bank fauna of Avalonia (Wales, UK)

“…In Teganium, the presence of a dermal or hypodermal skeleton that overlies small internal cavities surrounded by a very fine hexactin-based choanosomal skeleton is a relatively derived feature, although superficially similar to Cyathophycus . Teganium differs from Cyathophycus, however, in the irregularity of the primary skeleton, which is not tied to the sponge axis, and does not show quadruling; this is much more similar to the dermal surface structure seen in many extant hexactinellids (e.g., Chonelasma; Shen et al, 2022). Among known Palaeozoic fossils, Teganium is in some ways similar to the Hirnantian stem-group rossellids Matteolaspongia Botting, Muir, 2018 andShouzhispongia Botting, Janussen, Zhang andMuir, 2020; the latter also possessed similarly minute spicules.…”

Integrating Field and Ashore Knowledge to Fill the Gaps of Habitat Mapping in Unexplored Edges of the Pacific Ocean

“…Despite the advancements in technological tools and exploration endeavors many aspects of the deep-sea environments still being underknown. In the near future to fill the gaps in the most marginalized areas of the world what is important is establishing a trust relationship with local people, fostering at the same time the intangible and natural heritage preservation [12]. This is what extensively happened during the Nautilus Expedition season 2023, where the local communities held a pivotal role in each stage of the field mission accomplishment.…”