A New Polychaete, Scolelepis (Parascolelepis) Brunnea sp. nov. (Annelida: Spionidae), from Korea.

A new spionid polychaete, Scolelepis (Parascolelepis) brunnea sp. nov., from an intertidal mud flat in Korean waters, is reported. The new species is unique among species of Scolelepis Blainville, 1828 in having conspicuously long, reddish-brown branchiae on the anteriormost chaetigers. The new species is morphologically and genetically most closely related to Scolelepis (Parascolelepis) anterobranchiata Lee and Min, 2022 from Korea. However, the new species differs from the latter by a combination of the following characteristics: presence of reddish-brown pigmentations on anteriormost body, neuropodial hooded hooks appearing from chaetigers 21 to 22, larger size of worms, and three teeth above the main fang of neuropodial hooded hooks. Detailed description and images of the new species, along with three gene regions (cytochrome c oxidase subunit I [COI], 16S ribosomal DNA [16S rDNA], and 18S rDNA), are provided.

The complete mitochondrial genome of a marine polychaete, Prionospio cf. japonica (Annelida: Spionidae).

Prionospio Malmgren 1867 is one of the abundant genera of the family Spionidae Grube, 1850. Despite its rich diversity, information on their complete mitochondrial genome has remained unknown. In this study, we determined the complete mitochondrial genome of a spionid polychaete, Prionospio cf. japonica Okuda 1935. The specimen was collected from the fine sand in the intertidal zone of South Korea. The mitogenome consists of 15,267 base pairs, harboring 13 protein-coding genes (PCGs), 22 transfer RNAs, and two ribosomal RNAs. The maximum-likelihood phylogenetic tree based on the 11 PCGs showed that Prionospio cf. japonica grouped with other spionid polychaetes and formed a monophyletic group. Also, the mtDNA of P. cf. japonica was more closely related to that of non-polydorin spionid, Marenzelleria neglecta, than polydorin spionids. The molecular data will be valuable for studying evolutionary relationships among annelids.

Two new Scolelepis species (Annelida: Spionidae) from the Yellow Sea in Korea.

Two new spionid polychaetes of the genus Scolelepis from the intertidal habitats of the Yellow Sea in Korea are described and illustrated. Scolelepis (Parascolelepis) anterobranchiata sp. nov. is characterized by a combination of the following characteristic: palps with smooth globular expansions at the basal part, branchiae appearing in the anterior part of the body, absence of notochaetae in chaetiger 1, notopodial postchaetal lamellae partially fused with branchiae in anterior chaetigers, and neuropodial hooded hooks appearing from chaetigers 1819 with two pairs of teeth surmounting a well-developed main fang. Scolelepis (Scolelepis) rubra sp. nov. can be distinguished from its congeners by the following characteristics: reddish-pink body, presence of notochaetae in chaetiger 1, branchiae approximately twice as long as notopodial postchaetal lamellae, neuropodial bidentate hooded hooks usually appearing from chaetigers 2631, and presence of notopodial hooded hooks in posterior chaetigers. Based on molecular data, the sequences of the two new species showed relatively large genetic distances from other Scolelepis species in COI (15.819.5%) and 16S rDNA (4.915.8%). Morphological variability of prostomial shape in the genus Scolelepis is discussed for the first time.

Rhynchospioaciliata sp. nov., a new spionid species (Annelida, Spionidae) from the Korea Strait.

A new spionid polychaete, Rhynchospioaciliata sp. nov., was discovered in the fine sandy sediments of an intertidal habitat from Korean waters. The new species is considered a simultaneous hermaphrodite, but no brooding embryos were found in any of the specimens collected in this study. This species is unique in the absence of ciliation in the anteriormost chaetigers. Rhynchospioaciliata sp. nov. is morphologically most similar to Rhynchospiofoliosa Imajima, 1991 from Japan in having an elevation on the prostomium, conspicuously large and foliaceous branchiae, and intersegmental lateral pouches. However, the new species differs from the latter by the following characteristics: (1) large and lanceolate notopodial postchaetal lamellae of chaetiger 1, (2) transverse ciliated bands and ciliation on the inner branchiae absent in anteriormost chaetigers, and (3) pygidium with one pair of ventral cirri and numerous elongated dorsolateral cirri. Detailed description and illustrations of the new species are provided with molecular information on mitochondrial cytochrome c oxidase subunit I (COI), 16S ribosomal DNA (rDNA), nuclear 18S rDNA, and 28S rDNA.

New species of the genus Spio (Annelida, Spionidae) from the southern and western coasts of Korea.

A new spionid polychaete, Spiopigmentata sp. nov., is described from the southern and western coasts of Korea. This new species differs from its congeners by the combination of the following morphological characteristics: the presence of orange-brown pigmentation on the anterior part of the prostomium, black pigmentation on the peristomium and along the body, U-shaped nuchal organs, a comparatively long extension of metameric dorsal ciliated organs, three pairs of white dots per chaetiger, two to three posterior abranchiate chaetigers, and the presence of tridentate neuropodial hooded hooks. The partial 16S ribosomal DNA (rDNA) and nuclear 18S rDNA sequences of the new species and Spio sp. 2 reported by Abe and Sato-Okoshi (2021) from Japan showed high similarity, indicating that these two specimens belong to the same species. A detailed description and illustrations of the new species, together with molecular information, are provided.

The complete mitochondrial genome of Boccardiella hamata (Annelida: Polychaeta: Spionida).

In this study, the complete mitogenome sequence of Korean Boccardiella hamata was determined. This is the first complete mitogenome in the order Spionida. The complete mitogenome of B. hamata is 17,561 bp in length with 12 protein-coding genes (atp8 gene absent), 23 transfer RNAs, 2 ribosomal RNAs, and 1 control region. Interestingly, the gene arrangement of the 12 PCGs of B. hamata is unique, which is very different from that of the other polychaetes currently known. The phylogenetic tree supported the traditional taxonomic position of Spionidae within subclass Sedentaria.