Molecular phylogeny and morphological comparison of the deep-sea genus Alloptilella Li, Zhan & Xu, 2021 (Octocorallia, Pennatulacea)

Abstract

A previously described species and a new one belonging to the recently described sea pen genus Alloptilella Li, Zhan & Xu, 2021, are here described and illustrated based on a morphological and molecular study of materials collected in the Tasman Sea (SW Pacific) and at Puerto Rico (Caribbean Sea), respectively. The species, Alloptilella moseleyi comb. nov. (Kölliker, 1880) and Alloptilella williamsi sp. nov., are in overall agreement with the generic diagnosis of Alloptilella., based on the type species, Alloptilella splendida Li, Zhan & Xu, 2021. A single relatively large colony (55 to 95 cm in total length) is known for each of the three Alloptilella species. The transferred and the new species differ from the type species in having an opposite, rather than alternate, placement of polyp leaves along the rachis, colouration of autozooids, and mesozooids (in the case of A. moseleyi comb. nov.), and spicular features (e.g. maximum sizes in different parts of the colony, presence/absence of tentacular sclerites). Alloptilella williamsi sp. nov. is the first species of the genus recorded so far from the Atlantic Ocean, all other described species being western Pacific. A molecular comparison based on a set of concatenated sequences of four markers (three mitochondrial genes (mtMutS, ND2, and COI) and a nuclear segment (28S)) relates the species here studied to the published sequences of Alloptilella splendida, within the named Clade II of previous general phylogenetic studies on the octocoral Order Pennatulacea. Alloptilella is a monophyletic grouping, sister group of the genus Scytalium Herklots, 1858. The available molecular information of the genus Ptilella Gray, 1870, is reinforced with sequences (mtMutS, ND2 and 28S) from specimens of Ptilella inflata (Kükenthal, 1910) collected off the Namibian coast (SE Atlantic).