The authors sampled sediments along China’s southern coast from Zhejiang Province in the east to Guangxi Province in the west between 2019 and 2026. They collected material with a 0.05-square-metre grab sampler during high tide, washed sediment through a 0.5-millimetre sieve and preserved the retained specimens in 100% ethanol.

Morphological examinations included stereomicroscopy, compound microscopy, scanning electron microscopy and methyl green staining to identify glandular areas. DNA analyses covered five partial gene fragments: the mitochondrial COI and 16S rRNA genes and the nuclear 18S rRNA, 28S rRNA and H3 genes. Genetic distances were calculated with the Kimura 2-parameter model in MEGA X, and examined specimens were deposited at the Third Institute of Oceanography in Xiamen.

The complete holotype of B. multibranchia measured 47.78 millimetres long and 1.20 millimetres wide and had about 173 chaetigers. Diagnostic features included a short prostomial palpode, mixed chaetae in both rami of chaetiger 6 and numerous dorsal abdominal branchiae. The species was found in intertidal or shallow-water estuarine and inner-bay habitats containing mud, muddy sand or sandy mud.

Twelve B. multibranchia specimens from nine localities were sequenced. Within-species Kimura 2-parameter distances ranged from 0 to 4.3% for COI, 0 to 0.9% for 16S, 0% for 18S, 0 to 0.1% for 28S and 0 to 1.6% for H3. COI distances among specimens from Guangxi were substantially higher than those within the other sampled localities, suggesting possible population divergence that remains unconfirmed.

A sequence from Hainan was 1.3% from a paratype and fell within the observed within-species range, leading the researchers to assign that specimen to B. multibranchia. The new species differed from sequenced members of its genus by 22.3% to 44.6% based on COI. An 18S distance of 1.2% from B. lepte also exceeded the 0% within-species divergence recorded for B. multibranchia.

The complete holotype of P. simplex measured 20.11 millimetres long and 0.55 millimetres wide and had about 104 chaetigers. It lacked branchiae and differed from the previously described P. tenuis in having an areolated anterior thoracic epithelium and a clearly constricted transition between thorax and abdomen. The species is currently known from intertidal sites near Dadeng Island in Xiamen Bay and may occur in Fujian mangrove wetlands.

Two P. simplex specimens yielded all five gene markers, providing the first molecular data reported for the genus Parheteromastus. No within-species genetic variation was detected across the markers except for one nucleotide substitution in COI. The limited material available for this species restricts the extent of its documented geographic and genetic variation.

Detailed comparison with P. tenuis was also constrained because the earlier species had no published description or illustration of its abdominal hooks. In contrast, B. multibranchia was sampled across a wider geographic range and compared with available molecular sequences for other Barantolla species, although the higher COI distances among Guangxi specimens require further sampling to determine whether they represent a distinct population.

Subject of Research: Taxonomic description of two new Capitellidae species from southern China

Article Title: Two new species of Capitellidae ( Annelida , Polychaeta ) from the southern coasts of China

Article References: Lin, J.-H., García-Garza, M. E., Zhang, S.-Y., & Lin, H.-S. (2026). Two new species of Capitellidae (Annelida, Polychaeta) from the southern coasts of China. ZooKeys, 1292, 227-241. https://doi.org/10.3897/zookeys.1292.203560

Image Credits: AI Generated

DOI: 10.3897/zookeys.1292.203560

Keywords: Capitellidae, taxonomy, marine annelids, Polychaeta, new species, integrative taxonomy, morphology, molecular analysis, southern China, species, Annelida, southern