A gorgonian Nanji sea plume (Pseudopterogorgia nanjiensis) from subtidal zone of Nanji Islands

NEWS - During a benthic biodiversity expedition in the subtidal zone of the Nanji Islands in the East China Sea, researchers identified two specimens of Pseudopterogorgia as new species based on morphology and molecular features. Nanji sea plume (Pseudopterogorgia nanjiensis) most closely resembles P. fredericki in its irregular branching shape and unclear scaphoid.

Molecular phylogenetic analysis, based on mtMutS-COI gene sequences, delineated a monophyletic clade that includes all species of Pseudopterogorgia. Within this clade, P. nanjiensis shows close phylogenetic affinity to P. fredericki Williams & Vennam 2001 and P. australiensis Ridley 1884.

Members of the genus Pseudopterogorgia Kükenthal 1919 are widely distributed in shallow waters of the Indo-West Pacific. The location of P. nanjiensis is in the intertidal zone of the Nanji Islands with a water depth of 14 meters. This species is named based on the type location of the Nanji Islands and the colonies attached to rocky substrates with a water temperature of 18C and pH 8.13.

The genus Pseudopterogorgia is characterized by a pinnate or irregular branching structure, the absence of anastomoses and C-shaped or scaphoid-like sclerites present in the coenenchyma. Based on the branching structure and sclerite shape, this specimen is undoubtedly included in this genus.

P. nanjiensis, P. fredericki and P. australiensis are characterized by the absence of anastomoses and the presence of scaphoid-like sclerites in the coenenchyma. However, P. nanjiensis can be distinguished from P. fredericki based on sclerite morphology and is easily distinguished from P. australiensis based on irregular branching shape.

The addition of the new species P. nanjiensis found in the Nanji Islands, so there are currently a total of 8 valid species in Pseudopterogorgia. The precise phylogenetic placement of the genus Pseudopterogorgia remains essentially equivocal, mainly due to the low support values assigned to the corresponding nodes in the mtMutS-COI tree.

The 28S rDNA tree shows high support values for most internal branches, but the systematic position of Pseudopterogorgia remains unresolved. This uncertainty arises from the inclusion of sequences representing only 7 of the total 13 genera currently recognized within Gorgoniidae and is further compounded by the fact that many of these genera show polyphyletic or paraphyletic relationships.

The authors therefore suggest the need for further genomic data to achieve greater resolution. Such data should include a more complete collection of 28S rDNA sequences and potentially include highly conserved elements plus exons (UCE+exons).

Original research

Sun T, Xu Y, Xu K, Chen S, Xie S, Zhan Z (2024). A new gorgonian Pseudopterogorgia nanjiensis sp. nov. (Cnidaria, Octocorallia, Gorgoniidae) from the Nanji Islands, China. ZooKeys 1213: 237-249, DOI:10.3897/zookeys.1213.126841

Dlium theDlium