New insights and investigation: Morphomolecular notes on the infraciliature, taxonomy, and systematics of pleurostomatid ciliates (Protozoa, Ciliophora), with establishment of a new suborder, two new genera, and three new species
Zhang Gong-Ao-Te, 1中国海洋大学海洋生物多样性与进化研究所, 山东 青岛266003, 中国 2青岛海洋科学与技术中心, 海洋生物学与生物技术功能实验室, 山东 青岛266237, 中国 3河北大学生命科学学院动物系统学与应用重点实验室, 河北 保定071002, 中国 4上海海洋大学海洋动物系统分类与进化上海高校重点实验室, 上海201306, 中国 5沙特国王大学理学院, 动物系, 利雅得11451, 沙特 6英国自然历史博物馆, 生命科学系, 伦敦SW7 5BD, 英国, Zhang Teng-Yue, Chi Yong, Pan Hong-Bo, Zhang Zhe, Zhang Jia-Chen, Niu Jun-Hua, Ma Hong-Gang, A.S. Al-Rasheid Khaled, Warren Alan, Song Wei-Bo
Abstract
Pleurostomatid ciliates, as a highly diverse and widely distributed unicellular eukaryote group, play a crucial role in the cycling of nutrients and energy in microbial food webs. However, research on pleurostomatids remains insufficient, resulting in a paucity of molecular information and substantial gaps in knowledge of their phylogenetic relationships. In recent years, we investigated pleurostomatid diversity in various Chinese habitats, including their systematic relationships and taxonomic circumscriptions, which were comprehensively analyzed using an integrative morphomolecular approach. Results revealed that: (1) pleurostomatids can be categorized into two suborders, Protolitonotina <bold>subord. nov.</bold> and Amphileptina Jankowski, 1967; (2) Protolitonotina <bold>subord. nov.</bold> represents the ancestral pleurostomatid group and includes two genera, <italic>Protolitonotus</italic> and <italic>Heterolitonotus</italic> <bold>gen. nov.</bold>, characterized by right kineties progressively shortened along rightmost full kineties and absence of a left dorsolateral kinety; (3) <italic>Heterolitonotus</italic> <bold>gen. nov.</bold> represents an orphan lineage and is defined by an oral slit extending to its dorsal margin; (4) “<italic>Protolitonotus clampi</italic>” does not group with congeners but instead represents an orphan lineage, thus <italic>Novilitonotus</italic> <bold>gen. nov.</bold> is established to which <italic>P. clampi</italic> is transferred as <italic>Novilitonotus clampi</italic> <bold>comb. nov.</bold>; (5) three new species, <italic>Apoamphileptus paraclaparedii</italic> <bold>sp. nov.</bold>, <italic>Heterolitonotus rex</italic> <bold>gen. nov., sp. nov.</bold>, and <italic>Loxophyllum apohelus</italic> <bold>sp. nov.</bold>, are described; and (6) helices 21es6a to 21es6d within the V4 region of small subunit ribosomal RNA (SSU rRNA) may serve as a useful tool for discriminating pleurostomatids. The evolutionary relationships among all main lineages of pleurostomatids are discussed and a key to the identification of pleurostomatid genera is provided.