AUTHOR=Xu Ting , Sun Yanan , Wang Zhi , Sen Arunima , Qian Pei-Yuan , Qiu Jian-Wen 

TITLE=The Morphology, Mitogenome, Phylogenetic Position, and Symbiotic Bacteria of a New Species of Sclerolinum (Annelida: Siboglinidae) in the South China Sea

JOURNAL=Frontiers in Marine Science

VOLUME=8

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2021.793645

DOI=10.3389/fmars.2021.793645

ISSN=2296-7745

ABSTRACT=<p><italic>Sclerolinum annulatus</italic> n. sp. (Annelida: Siboglinidae) is described based on specimens collected from soft sediment of the Haima cold seep in the South China Sea. Morphologically, <italic>S</italic>. <italic>annulatus</italic> n. sp. is distinct in having a tube with transverse rings and a forepart (i.e., anterior region) containing one arched row of elongated plaques on both sides of the dorsal furrow. Genome skimming, assembly, and annotation produced a nearly complete mitogenome of <italic>S. annulatus</italic> n. sp. with 15,553 bp nucleotides that encodes 13 protein-coding genes, two rRNA, and 22 tRNA. Phylogenetic analyses based on the mitochondrial <italic>cytochrome c oxidase I</italic> (<italic>cox1</italic>) gene and a concatenated dataset comprising the mitochondrial <italic>cox1</italic> and <italic>16S rRNA</italic> genes along with the nuclear <italic>18S rRNA</italic> gene both strongly support the placement of <italic>S</italic>. <italic>annulatus</italic> n. sp. in the genus <italic>Sclerolinum</italic><xref ref-type="bibr" rid="B61">Southward, 1961</xref>. Based on <italic>cox1</italic>, <italic>S</italic>. <italic>annulatus</italic> n. sp. is most closely related to an undescribed siboglinid from off Kushiro in Japan (“Pogonophora” sp. Kushiro-SK-2003). Transmission electron microscopy, microbial <italic>16S rRNA</italic> amplicon sequencing, phylogenetic reconstruction, and stable isotope analyses together indicate that <italic>S</italic>. <italic>annulatus</italic> n. sp. hosts a single phylotype of sulfur-oxidizing endosymbionts.</p>